The program of research on building materials and structures, carried on by the

National Bureau of Standards, was undertaken with the assistance of the Central

Housing Committee, an informal organization of governmental agencies concerned with

housing construction and finance, which is cooperating in the investigations through a subcommittee of principal technical assistants.

CENTRAL HOUSING COMMITTEE

SUBCOMMITTEE ON TECHNICAL RESEARCH

Walter Junge, Chairman. A. C. Shire, Vice Chairman.

Federal Housing Administration. United States Housing Authority.

Sterling R. March, Secretary.

George E. Knox,

Yards and Docks (Navy).

Vincent B. Phelan,

National Bureau of Standards (Commerce).

Edward A. Poynton,

Ofl&ce of Indian Affairs (Interior).

George W. Trayer,

Forest Service (Agriculture).

Elsmere J. Walters,

Construction Division (War).

CHAIRMEN OF SECTIONS

Specifications Materials Maintenance

Carroll W. Chamberlain Elsmere J. Walters John H. Schaefer

Mechanical Equipment Methods and Practices

Robert K. Thulman

Albert G. Bear,

Veterans' Administration.

Pierre Blouke,

Federal Home Loan Bank Board (Federal Loan Agency).

Carroll W. Chamberlain,

Public Buildings Administration (Federal Works Agency).

Joseph M. DallaValle,

Public Health Service (Federal Security

Agency)

John Donovan,

Farm Security Administration (Agriculture).

NATIONAL BUREAU OF STANDARDS

STAFF COMMITTEE ON ADMINISTRATION AND COORDINATION

Hugh L. Dryden, Chairman.

Mechanics and Sound.

Phaon H. Bates, Gustav E. F. Lundell,

Clay and SiUcate Products. Chemistry.

HoBART C. Dickinson, Addams S. McAllister,

Heat and Power. Codes and Specifications,

Warren E. Emley, Henry S. Rawdon,

Organic and Fibrous Materials. Metallurgy.

The Forest Products Laboratory of the United States Department of Agriculture is cooperating with both committees on investigations of wood constructions.

[For list of BMS publications and how to purchase, see cover page III.]
UNITED STATES DEPARTMENT OF COMMERCE • Harry L. Hopkins, Secreta NATIONAL BUREAU OF STANDARDS • Lyman J. Briggs, Director

BUILDING MATERIALS

and STRUCTURES

REPORT BMS33

Plastic Calking Materials

by J. J. TREGONING, K. A. MILLIKEN, A. HOCKMAN,

w. H. SLIGH, and d. w. kessler

ISSUED JANUARY 20, 1940

The National Bureau ot Standards is a fact-finding organization;

it does not "approve" any particular material or method of construction. The technical findings in this series ot reports are to be construed accordingly.

UNITED STATES GOVERNMENT PRINTING OFFICE • WASHINGTON ' 1940

FOR SALE BY THE SUPERINTENDENT OF DOCUMENTS, WASHINGTON, D. C. • PRICE 10 CENTS
Foreword

The penetration of moisture through masonry walls is usually confined to joints

which were improperly filled or to joints which opened subsequent to construction on

account of structural movements. Joints which are particularly apt to open from structural movements are those between the masonry and frames of doors or windows.

Plastic calking materials have come into extensive use for filling certain joints in masonry

as well as in some other types of construction. They are intended to remain sufficiently

pliable to yield and maintain a seal in joints that vary in width to such an extent as to render the use of mortar or other rigid joint filler impracticable. Although the cost of the calking is relatively small, the failure to properly maintain a seal may result in costly

repairs.

Considerable difficulty has been experienced in obtaining entirely satisfactory

service from the plastic calking compounds, and hence a study has been made to devise

suitable tests for determining the qiiality of such materials. Tests for rate of hardening,

bond, tenacity, and shrinkage have been devised, and such determinations are of value

in showing the probable behavior in service. It has been found that their performance is influenced, to a large extent, by the nature of porous materials with which the com- pounds are placed in contact. There is a marked variation in uniformity of all brands

studied, which indicates that more rigid control is necessary in the manufacture of such

products.

Lyman J. Briggs, Director.

nil
Plastic Calking Compounds

\by J. J. Tregoning, K. A. Milliken, A. Hockman, W. H. Si,ic;h, and

' D. W. Kessler

CONTENTS

i Page

I. Introduction 1 II. Samples 2

III. Composition studies 2

1. Methods 2

2. Analytical results . 2 IV. Physical determinations 4

1. Current tests 4

2. Proposed tests 5

(a) Shrinkage 5

(b) Bond 6

(c) Tenacity 6

(d) Rate of hardening 6

(e) Oil retention 7

(f) Consistency 7

(g) Density 7

(h) Volatile loss 7

3. Comparison of results of current and proposed tests 7

ABSTRACT

One phase of this study was concerned with the de- velopment of test procedures and the accumulation of data to form the basis of a specification. By inspection of several installations and numerous specimen

joints after exposure to the weather for several years,

it was decided that tests for shrinkage, rate of hardening, bond, tenacity, staining, and slumping tendency

afford a good basis for predicting the performance.

Since calking compounds are commonly used in contact with porous materials whose absorptive properties

materially affect the performance, it is necessary to employ an accessory porous material in the tests. For

this purpose a certain limestone has been selected be- cause of its uniformity. The test procedures have

been so devised that three specimens are prepared for each sample and on these eight properties are deter- mined.

A study of the composition of proprietary compounds

has shown that a large variety of formulations are used.

Oils most commonly used are fish, soybean, linseed,

and tung. Cottonseed and rapeseed oils were employed in some mixtures whereas there were a few

brands in which the vehicle consisted of rosin, tallow,

or synthetic resin. In a considerable number of the

proprietary compounds, the volatile content was too

high for good performance. A study of compositions

in relation to performance has indicated that pretreatPage

V. Relation of type of building material and width of joints to performance 8

Vl. Relation of composition to performance _ 10

1. Vehicle 11

(a) Linseed oil 11

(b) Soybean oil 12

(c) Fish oil 13

(d) Tung oil 16

(e) Miscellaneous 16

2. Pigments 16

3. Thinners 16

VII. Relation of physical properties to per- formance 17

VIII. Primers and their effectiveness 18 IX. Durability 19

1. Exposure of strain-test .specimens. , 19

2. Exposure of rigid joints 20

3. Inspection of buildings 20 X. Summary 22

ment of the oil is of first importance, and that considerable care must be exercised in selecting fillers as well as keeping the volatile content very low. Certain factors which may affect the performance of plastic calking materials in service have been studied. Compounds that give good service in one type of masonry do not always give similar results on all other

types. Often very porous masonry absorbs less of the

vehicle than much denser materials do. Capillary

forces of the pores seem to be of considerable importance. A compound may be satisfactorj^ in wide joints

but fail in narrow joints. Primers have been found to have some value in reducing shrinkage of mixtures of pronounced staining characteristics, but they may

affect the bond adversely. Good mixtures do not

require primers.

I. INTRODUCTION

The purposes of this investigation of calking

compounds were (1) to develop simple test procedures and obtain data for use in specifications, (2) to study compositions and physical

properties in relation to performance, and (3) to study the installation and service conditions

which have a bearing on performance and

durability.

[1]
A large number of commercial samples were

collected and numerous experimental compounds were prepared in the laboratory.

Chemical analyses were made of the commercial

compounds. Physical tests were made on both

commercial and experimental compounds. The

tests now used in certain specifications were employed as a guide in determining the specific

properties which give suitable indications of quality. Laboratory studies have been supplemented, as far as possible, with exposure

tests and inspections of actual installations.

II. SAMPLES

Forty producers cooperated by supplying

samples of their products. In several cases, two or more samples of the same brands were

obtained at different times in order to determine the causes of certain undesirable properties. One hundred and ninety experimental

compounds were prepared for a supplementary

study of compositions.

A large number of samples submitted for test

in connection with various Government construction projects were utilized for comparing

the results of current tests with those of certain new tests which will be described later. Exposure tests, started at intervals during the past

8 years, were examined for information on

quality. The specimens consisted of grooves

m limestone blocks filled with the compounds.

About 50 brands of calking are represented in these tests, and there are more than 100

specimens of some brands.

III. COMPOSITION STUDIES

1. Methods

The methods used in the chemical examination of commercial calking compounds are

briefly outlined as follows:

(a) The volatile matter was determined by

spreading 5 to 10 g of the calking compound in a thin layer in a tin dish about 2^ in. in diameter, which had previously been weighed,

weighing, heating the dish and contents for

3 hr at 105° C, and reweighing. The loss in weight at 105° C was regarded as "volatile,"

and from this figure the percentage of volatile was computed.

(b) The percentage of pigment was determined by weighing accurately about 15 g of the compound in a centrifuge tube. Fifty

milliliters of extraction mixture (10 volumes of ethyl ether, 6 of benzol, 4 of methyl alcohol,

1 of acetone) was added and the sample

thoroughly disintegrated in the solvent. The

tube and contents were centrifuged rapidly for

5 min. The clear supernatant liquid was decanted into a casserole and heated to remove

volatile constituents from the nonvolatile vehicle. The extraction was repeated two more

times. The tube and pigment were then

heated at 100° C for 3 hr, cooled, weighed, and

the percentage of pigment calculated. The

pigment was examined petrographically to identify its ingredients.^

(c) The percentage of nonvolatile vehicle was determined by difference.

The identification of the type of saponifiable

oil in the vehicle and its method of bodying, as given in table 1 , were based on suitable chemical

and physical methods The viscosities of the

vehicles were estimated by comparison with

Gardner-Holdt standards, after the extracting

liquid had been removed from the vehicle.

2. Analytical Results

Table 1 contains the results of the chemical

analyses of 72 commercial calking compounds.

Most of them consisted of finely ground and

fibrous materials (the pigments) mixed with a drying or semidrying oil and some volatile

thinner (the vehicle). A great variety of materials were identified in the finely ground

portion of the pigments, calcite being the most

common, but quartz, lithopone, zinc sulfide,

dolomite, and diatomaceous silica were also used. The fibrous material was usually as- bestos in the medium-short fiber grades of the

crysotile or tremolite varieties. The amount

of pigment varied from 28 to 88 percent.

The vehicles in a few compounds were mineral oil, sulfurized oil, tallow, rosin, or cotton- seed pitch. Mineral spirits was the most

commonly used thinner, but kerosene was

used in two of the samples. The amount of

volatile matter varied from 1 to 37 percent.

I The authors are indebted to H. F. McMurdie for the petrographic

exaTninations.

[2]
I

The treated oils used in the commercial

calking compounds could not be identified as accurately as untreated oils. Because of the

changes in the physical and chemical characteristics of oils which occur in the different

motliods of bodying, the identification of the

bodied oils was sometimes uncertain. Ttie oils in seven commercial compounds could not be

identified, but the characteristics oi' others

classified them into definite groups.

Table 1.Composition and physical studies on 72 commercial samples of plastic calking

Pigment

Nature ^

Vehicle

Nonvolatile

Major constituent aso o

Shrinkage

at IT) days ' Stain on

' Condition of pats on lime- stone >>

COMPOSITIONS CONTAINING LINSEED OIL

87

Calcite and chrysotile

Calcite and chrysotile Lithopone, calcite, and chrysotile Calcite and lithopone

Calcite, amphibole, and chrysotile

Calcite, amphibole, lithopone, and

chrysotile. Chrysotile and amphibole

Calcite, amphibole. and chrysotile Tremolite and zinc oxide

Calcite Tremolite, calcite, and feldspar

Calcite Zinc oxide, chrysotile, and tremolite

Calcite - Calcite

% % in. % %

30 Apparently blown lin- Vi 1 0. 00 6.9 2.5 SS S B, T, \V 1 seed.

34 do V, 1 .03 4. 2 3.2 OK s T-W 1-2 40 do --- Vi 6 .00 14.7 4.6 OK s Th-W 2

25 do Vi 6 .00 5.2 OK s Th-W 3 27 do V2 6 .21 "6.4 4.5 OK OK Th-W 2-3

24 do Vi 3 . 16 2.4 OK ss Sm-Th 2-3

33 do Vi 7 .28 5.5 2.5 OK OK Th'W 2-3 45 do Vi 5 .18 0.4 3.2 OK OK T-W 1 36 do Vi 10 .07 10.6 8.3 OK SS Th-W 2-3

14 do Vi 2 .01 .•i. 5 2.3 OK s Th-W 2-3

29 do V, 12 . 16 10.8 7.0 OK OK Th-W 3

21 do V, 1 .08 5.6 2.0 OK ss Th-W 2-3

31 Apparently polymerized Vi 9 .00 15.4 5. 9 OK OK T-W 1 linseed oil. 11 do Vi 1 .08 6.4 2. 3 OK OK B-Th-W 2

12 do Vi 1 .02 2.9 1.6 OK OK B-Th-W 2 COMPOSITIONS CONTAINING SOYBEAN OIL

35 Apparently blown soy- Vi 12 0. 05 12.3 7.4 OK S

bean oil. 30 do Vi 13 . 12 18.4 5.8 OK S

27 do Vi 13 .18 11.5 6.4 OK s

30 do Vi 10 .00 20.3 6.3 OK (') 23 do V, 9 .00 17.7 6. 1 OK OK

38 do Vi 14 .04 17. 7 8.7 OK OK

43 do Vi 10 .07 12.3 6.4 OK OK

20 do.-_ Vi 1 .01 2.2 1.7 OK OK

42 do Vi 11 .05 9.6 4.9 OK OK

42 do Vi 9 .00 9.8 6.0 OK OK

36 do Vi 9 .00 11.8 5.0 OK OK

38 do Vi 14 0. 02 24.0 9.7 OK ss

45 do Vi 12 .23 16. 1 9.5 OK ss

41 do V, 2 .39 3.6 3.6 OK OK

Amphibole and lithopone Diatomaceous silica, chrysotile, and

amphibole.

Lithopone, amphibole, and chrysotile Quartz, chrysotile, and amphibole

Quartz, chrysotile, and amphibole

Amphibole, quartz, and chrysotile

Calcite, tremolite, and chrysoltile Calcite

Calcite, chrysotile, and opaque material

Calcite, chrysotile, amphibole, and

opaque material.

Calcite, chrysotile, and opaque material

Calcite, chrysolite, and amphibole

Zinc oxide and chrysotile

Calcite, chrysolite, and amphibole

Th-W

Th-W

Th-W

T-W

Th-W

T/i-TT Th-W

"Th-W"

Th-W

Th-W\\.\ Sm-Th.

Th COMPOSITIONS CONTAINING FISH OIL

27 Apparently blown fish Vi 17 0.07 18.4 11.8 OK S

oil. 26 do Vi 25 .02 24. 7 12. 1 OK s

29 do Vi 18 .09 22.7 11.9 SS s

21 do Vi 8 .00 18. 2 6.0 OK OK

24 do Vi 15 .00 17.0 10.1 OK s

59 do Vi 7 .21 8.8 4.5 OK OK

39 do Vi 7 . 13 9.8 4. 1 OK OK

33 do Vi 11 . 11 13.5 9.6 OK OK

33 do Vi 11 .17 14.6 9.8 OK OK

30 do Vi 23 .06 19. 5 11.7 OK S

19 do Vi 3 . U 12.0 2.2 OK OK

33 do Vi 10 . 12 8.9 7.5 OK S

45 do Vi 1 .24 6.3 3.7 OK OK

46 do Vi 11 . 15 14.6 9.2 OK OK

20 do Vi 1 .21 2.9 1.0 OK OK

37 do Vi 13 .13 14.2 9.4 OK OK

32 do Vi 8 . 10 9.9 5.4 OK OK

33 do Vi 8 . 19 10.9 7.0 OK OK

35 do (') 5 .09 6.4 4.0 OK OK

38 do (-) 13 . 13 12. 1 .5.0 OK S

16 do... (=) 8 .00 10.0 5.3 OK s

IS D-g... 56 ISA-g... 49

53

8 C-g 71 IS E-k... 61 16A-g.... 34

17 A-g... 54 18A-g..- 56

18 B-g. .__ 56

IS E-g.... 47

IS F-k_^ 78

IS G-g ... 57

16 B-g. . . 54

16 D-g___. 43

17 B-k___ 79

19 A-g.._ 50

20 A-g.-, 60

20 B-g...- 59

18 C-/C.... 60

21 A-g... 49

22 A-k... 76

Dolomite, calcite, chrysotile, and amphibole. Calcite and chrysotile

Calcite, chrysotile, and amphibole

Calcite and chrysotile

Calcite, chrysotile, and tremolite

Calcite, cotton fibers, and chrysotile

Calcite Cotton fibers, calcite, and chrysotile Chrysotile, calcite, and dolomite

Calcite and chrysotile Calcite and dol(imite

Calcite, tri niolitc, and chrysotile

Calcite and anipliibole

Calcite, amphibole, zinc oxide, and

chrysotile. Amjjhibole and calcite Calcite and chrysotile

Calcite Chrysotile and calcite Calcite, chrysotile, and amphibole

Amphibole and chrysotile

Calcite, amphibole, and lithopone

Sm-Th

Sm-Th

Th-W. Th-W.

Sm-T.

fh-W. Sm-Th

Th-W.

See footnotes at end of table.

[3
Table 1.

Composition and physical studies on 72 commercial samples of plastic calking—Continued

Sample

designation

Pigment

Nature

Vehicle

Nonvolatile

Major constituent

1.^

Shrinkage

at 15 days Stain onCondition of pats on lime- stone

COMPOSITIONS CONTAINING TUNG OIL

%

18 C-g..-- 60

18 D-k... 83

18 E-k.... 85

23 A-g.-- 61 U A-g.... 54

Calcite and chrysotile

Calcite do

Calcite, quartz, and chrysotile Talc and calcite

Apparently polymerized tung oil. do

do

do Apparently polv. tung & fish oil.

% in. % %

V, 11 0. 25 6.3 4.

1

OK OK B-T-W...

Vi 3 .01 4.0 1.7 OK OK do

Vi 3 .37 3.2 1.7 OK OK Th-W

Vi 11 .31 8.7 4.6 OK ss Th-W

V, 16 . 13 16.7 9.5 OK OK B-Th-W

1-2

1-2

1-2

2

COMPOSITIONS CONTAINING MISCELLANEOUS VEHICLES

25 A-k.

US B-g.

26 A-g^

27 A-g.

27 B-g^

S7 C-g.

16 E-g.

16 F-k_

28 A-g.

29 A-k^

SO A-g.

SO B-g_

SO C-k.

SO D-g.

50 E-g.

51 A-g.

32 A-g.

Chrysotile and lithopone

Chrysotile and lithopone

Tremolite. feldspar, and lithopone Opaque material Opaque material Opaque material Amphibole, calcite, chrysotile and

quartz. Amphibole and chrysotile Lithopone and chrysotile Talc, chrysotile, calcite, and amphiboleCalcite, amphibole, and chrysotile Calcite and chrysotile Calcite Amphibole, calcite, and chrysotile

Calcite, chrysotile, amphibole, and zinc oxide Magnesite and chrysotile Calcite

Apparently rapeseed oil. ____do Apparently blown cot- tonseed oil. Cottonseed pitch -__-dodo Apparently sulfurized

oil.do Apparently rosin Apparently tallow Unknown

do

do

dodo

.do-

.do.

V, 17 0.01 13. 6 6.0 OK S (i) V, 16 .01 16.0 7.0 OK s (') V, 6 .37 9.4 6.8 OK OK Th-W 2

(«) 37 . 10 36.2 20.6 OK s (0

(•) 26 .02 34.2 l.'i.7 OK s (0 « 10 .01 7.3 2.2 OK s (0

4 .02 11.3 2. 5 SS ss T-W 1

1 .02 4. 2 2.

1

OK OK Sm-Th 1

(') 1 .29 OK ss B-Th 1 w 3 .38 OK OK B-Sm-T 2 v. 18 . 18 16. 2 8.1 OK ss B-W. 2 V, 14 .00 18. 5 7.5 OK OK Th-W 9 V3 1 .00 8. 2 1.7 OK s (0 Vz 14 . 17 13. 6 5.6 OK OK Th 2 V, 16 .00 21. 5 9.6 OK OK Th-W 1-2

v. 15 .02 13.8 8.5 OK OK Th 2-3 V, 15 .00 6. 4 1.7 OK OK B-Sm-T.. 1

« Numbers designate particular manufacturers; letters A, B, C, etc., different samples or brands; g and k stand for gun grade and knife grade respectively; e.g. manufacturer 2 submitted 2 gun-grade samples, designated 2 A-g and 2 B-g.

k Calcite includes the various forms of whiting such as chalk whiting, precipitated whiting and ground limestone. Chrysotile is a variety of asbestos while the minerals identified as amphibole and tremolite are mainly mixtures of fibrous (absestos) and nonfibrous particles. {Vi, in range A to T (Gardner-ITnldt standards).

U', in range Via I' (Gardncr-llnjiit standards).

Vz, in range Z^to Z6 (Gardner-Holdi standards),

i Volatile by method described in section III, 1—This ingredient was apparently mineral spirits except in samples 25A and 25B.

• Not determined.

' Shrinka.ge of H-in. layer of plastic on limestone; H-in. layer on glass,

e OJ['=satisfactory; .SS=slight stain; i9=stain. These observations were made at end of first year, on specimens stored in the laboratory. B=brittle, Sra=smooth, T=thin, 2'/i= thick, wrinkled. Numerals signify hardness, namely, 7=satisfactory, 2=hard, 3=very hard. Two figures, 1-2, signify intermediate hardness,

i Specimen hard throughout.

IV. PHYSICAL DETERMINATIONS 1. Current Tests

The tests used heretofore in connection with

specifications have been of value in determining

tlie early behavior of materials under conditions

similar to those of service, but some of them are cumbersome and do not afford the desired in- formation as to the cause of poor performance.

Hence a series of simpler tests has been devised

which it is thought wUl determine the quality

of calking compounds more easily and defi- nitely. A satisfactory means of testing these

products without an accessory porous material

has not been found, and hence a particular

limestone is used for this purpose.

Tests ^ used during the past 8 years consist of

(1) a strain test (see fig. 1) made on a joint

between two slabs of a designated limestone;''

(2) a stain test on limestone (see fig. 2, D and F)

and marble; (3) a slump test (see fig. 2, E); and

(4) a copper corrosion test. The requirements

are that a Ya-vo.. joint in the strain test can be

extended (stretched) 0.05 in. without breaking

the seal, that the plastic in a groove % in. wide

^ .4 test procedure for plastic calking mater i lls, Proc. Am. Soc. Testing

Materials 35, pt. 2, 581 (1935).

3 This limestone is produced by the Rockwood Alabama Stone Co.,

Russellville, Ala., and is designated as "veinless gray" from the Aday

quarry. Before use in any of the tests the stone is dried for 24 hr at 105° C.

4]
and Yi in. deep in a block of limestone shall not

slump or flow when the filled groove is placed

in a vertical position for 24 hr at room temperature followed by 24 hr at 50° C (122° F), that

oil shall not separate from the plastic and stain

the limestone block used in the slump test or spread around a pat placed on white marble,

I

and that the plastic shall not discolor a bright

copper plate when a pat is left on the surface

for 5 days.

2. Proposed Tests

Physical properties which are believed to have a bearing on performance are (a) shrinkage, (b) bond, (c) tenacity, (d) rate of hardening,

(e) oil retention, and (J) consistency. Density

and volatile loss of the plastics are obtained in connection with the shrinkage determination.

Since these procedures have not been published heretofore, they are described here in

detail.

(a) Shririkar/e

This property is detenniiied by means of a

brass ring 2% in. in diameter and }i in. high

(volume, V, known to nearest 0.01 ml), a

ground-glass cover plate and a slab of limestone

3% by 3}^ by % in. (see fig. 2,C). The combined

weight (ll'i) of the ring, slab, and cover plate

is determined (all weights to 0.01 g); then the

ring is centered on the slab, and a Ys-va. layer *

of the plastic is spread inside the ring to form

contact with the stone and rmg, and the weight

(W2) determhied (with cover plate). The portion of the ring above the plastic is then fiUed

' A tool used for spreading and gaging the thickness of the layer is made from a piece of brass i by M by H in. At IH in. from one end a

slot } s in. wide and 5 s in. deep is cut perpendicular to one edge. From

the slot to the nearer end the edge of the metal is cut back for H in. The

sharp corner between the notch and the new edge is rounded and beveled

slightly for the purpose of producing a fiUet with the calking where it joins the ring. The tool is held with the notch over the edge of the ring and the short end inside the ring. The edge outside the ring is held

firmly against the stone slab as the tool is moved around to level the calking sample.

Figure 1.Strain-testing devices. A, horizontal type; K, vertical type, showing strain gages C and F with specimens in position for testing. D is a specimen joint used in type .1, and G

shows the accessory materials for making a joint for type E.

[5]
with distilled water, so there are no air bubbles

when the cover plate is in place and this weight

(IF3) is determined. Since the volume of 1 g

of water is approximately 1 ml, the volume of

the plastic Vc=V- iWs + W2). The water is then poured off and the sample exposed to the

air for 15 days, after which the weights W2'

split, leaving a soft layer in contact with the

stone. This property may be also determined by

spreading a )8-in. layer of the plastic on a slab

of limestone and after submerging the specimen

in water for 2 days. If the bond is unsatisfactory, blisters will form in the plastic.

Figure 2.

Apparatus and specimens.

A, penetration specimen; B, penetration apparatus; C, shrinkage specimen and equipment. B, E, and F. are perrormanee tests in which D shows no slump or stain, E shows slumping, and F shows staining.

and W3', corresponding to W2 and W-s, are determined. The volume shrinkage is (W3' —

W2')—{W3—W2) and this times 100 divided by

Vc is the percentage of shrhikage.

{b) Bond

The bonding value of the plastic is estimated

from the shi-inkage specimen after removing the

ring. One-fourth of the plastic is loosened from

the stone with a spatula and pulled upward.

If the plastic peels off, the boncUng property is not satisfactory. A satisfactory sample will

(c) Tenacity

This may be deternihied on the sample used

for shrinkage. The portion loosened for the

bond test is folded over on the remaining part

and creased three times (bent 180°) along the same line. Embrittlement, or lack of tenacity,

is indicated if the specimen breaks or cracks.

(d) Rate of Hardening

This is determined with a penetrometer (see

fig. 2, B) on a joint between limestone slabs

spaced % in. filled with the plastic to a depth

[6]
of 1}^ in. and length of 3^ in.^ The apparatus

is the same as that required for determining

the penetration of bituminovis materials (ASTM

standard D 5-25, penetration of bituminous

materials),® except that the weight on the needle

point is rediiced to 12.5 g. The depth to which

the needle penetrates the plastic in 5 sec is recorded for three trials made near the middle

of the joint. After curing the joint for 15

days, the skin is removed and three more penetration readings made. The hardening is computed from

h=

in which h is the rate of hardening, Fj and P2

are respectively the averages of the original

and final penetrations.

(e) Oil Retention

This is rated from the specimen used to determine rate of hardening by measuring the

distance on either side of the calking that the

limestone is discolored.

(/) Consistency

Since the principal concern of the buyer in regard to consistency is whether the material

will flow from the joints or sag, this test is made to simulate service conditions. A joint

specimen is made between the same two slabs

* Three penetration readings are made along the center Hne of the

joint, as soon as the specimen has been prepared, by determining the depth of penetration in 5 sec. The position of the points for test are

selected so that the first is about % in. from one end of the joint, and the

other two are spaced at intervals of about in. The specimen is then

stood on edge with the joint horizontal and aged for 15 days, .^fter removing the skin from the calking material, three penetration readings

arc made at points % in. apart, the first being % in. from the end opposite

to that used for the first penetration.

* Am. Soc. Testing Materials standards, nonmetallic materials, pt. 2, p. 1080 (1936).

of limestone used for the rate of iiardening test

(see fig. 2, A). The space filled is % in. wide,

lYi in. deep, and 3^ in. long. The joint is placed in a vertical position with no support

below the plastic. The amount of sag is measured from the lower face of the stone to the lowest point assumed by the plastic after storing 1 day at room temperature and 1 day

at 50° C (122° F).

{g) Density

Density is computed from the data obtained

in the shrinkage test as follows:

^~

V,

'

(h) Volatile Loss

The loss in weight of the specimens used for the shrinkage test is considered as the volatUe

loss. This is reported as a percentage by

weight of the sample, and is computed from

v^iW2-W2')l00KW,-Wr)7

3. Comparison of Results of Current and

Proposed Tests

Table 2 gives results of physical tests on 26

samples of trade brands and also on 25 experimental compounds made in the laboratory.

The trade samples were submitted for various

Government projects between April 1938 and

February 1939. Laboratory mixtiu-es show

typical results for those made in this investigation. The data indicate that the shrinkage

and rate of hardening values were lower for experimental than for commercial compounds,

indicating a probability of better performance

in service.

' The percentage of volatile determined in this way is less than that determined by heating at 105° C (the basis for "volatile" in table 1),

185644°—40 2 [7]
Table 2.

Results of physical tests i on commercial and experimental compounds

[All gun-srade samples]

Qomiilo rl oci (rn Q f inn 2 Strain

Stain on ^ Slump

Shrinkage

Volatile

loss (by

weight) Bond 3 Tenacity '

Penetration Rate of harden- Lime- ing stone Aiarble Original Final

in. % % 0.01 cm 0.01 cm /o ClC2

0. 40 OK OK OK 3. 8 0.

1

OK OK 58 41 29

. 30 OK SS OK 13. 9 4. 0 OK 243 134 45 cs . 24 OK OK OK 8. 2 2. 2 nUJ\V 150 76 49

46 Oi OK OK OK 12. 9 1. 7 OK OK 170 92 C5 '. 14 OK OK OK 20.2 6.

1

OK OK 212 106 50 C6 . 11 OK S OK 17. 5 6. 4 OK OK 224 108 52 €7 . 12 OK OK OK 8. 9 2. 2 OK OK 83 38 54 CS . 16 OK OK OK 19. 8 6. 7 OK OK 282 134 52

31 OK OK OK 6. 2 0.

1

OK OK 138 67 51 CIO '. H OK OK OK 13. 5 9! 5 OK OK 238 103 57 Cll . 20 OK OK OK 10. 3 1. 6 OK OK 251 129 49 C72 . 31 OK OK OK 9. 4 1. 6 OK OK 224 120 46 CIS . 04 OK OK OK 25. 1 12. 4 F F 273 67 76 04 OK OK OK 24. 0 9. 4 OK F 275 93 66 CIS 45 !oo OK OK OK 27^ 0 13! 7 OK OK 210 115 C16 . . 04 OK S OK 23. 0 8. 5 OK OK 242 95 fil C17 . 02 8S SS SS 7. 2 0. 2 F F 95 19 QHoU CIS .._ . GO OK OK OK 26. 2 10. 8 OK OK 160 60 C19 . 01 OK s OK 16. 7 6. 2 OK F 97 38 61 CSO- - - !03 OK OK OK 22! 3 10] 5 OK OK 250 87 65 C21-^^ _ _ . 00 OK OK OK 20. 2 6. 7 F OK 232 74 Do C2t--- _ . . ... . 04 OK OK OK 22. 4 5. 2 F OK 163 68 58 ... . 03 OK OK OK 6. 0 0. 2 OK F 135 46 66 C2^ 00 OK OK OK 7. 2 0 0 p F 258 45 83 C25 !oo OK s OK 4. 2 0^6 F F 163 24 85 K103 , . 20 OK vs OK 7.

1

0. 0 OK OK 160 138 14 E16G _ _ . 24 OK OK OK 4. 8 0. 0 OK OK 225 130 42 E1G7 - . - ... ... . 10 OK VS OK 12. 7 1. 9 OK OK 278 137 51 B168 . 17 OK OK OK 11. 6 1. 3 OK OK 255 106 58 Em . . !7 OK VS OK 13! 0

{.'7 OK OK 159 70 56 E17i _- - __ . 12 OK vs OK 14. 7 1. 9 OK OK 155 82 47

. 26 OK OK OK 5. 0 0. 0 OK OK ^290 230 21 E173. _ .__ . 27 OK OK OK 7. 6 0. 7 OK OK 273 170 38 E17^ . 27 OK OK OK ] 1. 5 1. 5 OK OK 265 169 36 E175 !40 OK OK OK 13! b l!9 OK OK 223 146 35 _

. 36 OK OK OK 16. 0 1. 5 OK OK 214 130 39

. 03 oo SS OK 25. 2 3. 2 OK OK 205 130 37

. 00 .9 s OK 22. 0 0. 0 F F >290 88 70 E179 . 18 OK VS OK 12. 8 3.3 OK OK >290 222 23 Eisn . . 10 ss s OK 12. 3 0. 6 OK OK 286 242 15 E181- .22 OK OK OK 13.4 3.

1

OK OK 290 225 22 E182 .22 OK OK OK 11.3 1.9 OK OK >290 244 16 E18S .24 OK OK OK 13.

1

4.4 OK OK 283 213 25 ElSi .26 OK OK OK 10.6 2.4 OK OK 225 187 17 E/S5 .25 OK OK OK 10.4 2.3 OK OK 202 126 38 Em . 15 OK OK OK 16.9 4.5 OK OK 259 188 27 E187 .26 OK OK OK U. 5 2.8 OK OK 249 152 39 E188 . 25 OK OK OK 13.2 3.1 OK OK 261 134 49 E189 .33 OK OK OK 8.8 1.6 OK OK 245 144 41 E190 .45 OK OK OK 12. 5 3.8 OK OK 202 113 44

' strain, staining, and slump tests were made by the methods described in section IV, 1; the other tests were made by the methods described in section IV, 2.

2 Commercial samples designated by C; experimental, by E.

3 OA:=satisfactory; VS= very slight; ^'=failure; S=stain; S.S'=sIight stain. The average and range values for commercial

and e.xperimental compounds are given in table 3. Table 3.

Average and range values for coynmercial and

experimental compounds

Compounds

Shrinkage Rate of hardening Volatile loss

Average Range Average Range Average Range

Commercial

Percent

15

12

Percent

4 to 27

5 to 25

Percent

60

36

Percent

29 to 85

17 to 70

Percent

5

2

Percent Oto 14 Oto 4 Experimental

V. RELATION OF TYPE OF BUILDING

MATERIAL AND WIDTH OF JOINTS

TO PERFORMANCE

The performance of calking compounds on

different types of building materials is influ- enced by the porosity and the capillary forces

in the pores. Shrinkage and hardening of the

mastics, are to a large extent, caused by the

loss of some of the vehicle. Porous materials

in contact with calking compounds may absorb

[8]
a sufficient amount of the oil to cause excessive

shrinkage and hardening, whereas the same

plastic in contact with less porous materials

may give satisfactory results (see figs. 3 and 4). On the other hand, the mastics adhere more

tenaciously to porous materials. Wlien a joint

is made between brickwork and a metal and

excessive shrinkage occurs, the mastic will usually separate from the metal. Furthermore, the ability of the mastics to remain in a

vertical joint without slumping is affected by

porosity and capillary forces. Workmen prefer

a calking material that can be easily applied

with a gun. Producers naturally cater to their

customers and make the mixtures as soft as

possible. This sometimes leads to trouble,

because a mixture that will remain in joints

between absorptive brick may flow out of

joints between marble or other less absorptive

materials.

Figure 5 illustrates the manner in which a

calking compound may flow from vertical

joints between dense bricks, whereas the same

plastic remams in place between porous bricks.

Figure 6 shows similar results when a calking

compound was placed in vertical joints ranging

from nonporous on the left to very porous materials on the right. Figure 7 shows the progressive shrinkage of three commercial calking

compounds on glass and on limestone over a period of 30 days, and figure 8 shows the shrinkage of six samples on limestone for 10 months.

The shrinkage on glass is assumed to be caused

entirely by evaporation of volatile thinner,

whereas that on limestone is the result of volatilization and absorption of vehicle. For samples referred to in figure 7, the loss of volatile

caused more than half of the shrinkage. Mixtures of low volatile content shrink mainly

from loss of oil to adjoining materials, and if in contact with nonporous materials or porous

materials of low capillarity, such mixtures

show little shrinkage.

Calking materials give better results in wide

joints between porous materials than in narrow

joints. Figure 9 shows one calkmg mixture in

joints between limestone slabs where the joint

widths vary from }^ in to }^ in. The narrow

Figure 3.

Staining of various materiaU b;/ one calking mixt lire.

The irregular stains on brick (8), limestone (6), concrete (4), and marble

(1) probably indicate variations in the capillary properties of these

materials. Cracks formed in the joints between the materials which

absorbed considerable amounts of oil.

joints show excessive shrinkage and cracking.

The actual amount of oil absorbed from the

calking was about the same for all joints, but

the total amount of oil in the plastic requked

to fill a narrow joint is less than that for a wide one. For example, if a ^s-in. joint and a

}^-in. joint are filled with the same mixture,

there will be only one-fourth as much in the

[9]
Figure 4.

One calking compound between dense bricks (light colored) and more porous bricks.

Cracks formed between most of the porous bricks within a few days, whereas the calking compound was in good condition between the dense bricks.

first as in the second. Usually plastic calking

in joints less than % in. wide is not very satis- factory. When it is necessary to calk very narrow joiats or cracks, one should use a

plastic containing very little volatUe and an

oil that will not stain. A somewhat stifl:"er mixture is required for wide joints in order to prevent sagging.

VI. RELATION OF COMPOSITION

TO PERFORMANCE

Table 1 gives the results of composition

studies and physical tests on 72 commercial

compounds. The data on volatile and shrinkage were determined by methods which were changed later to simplify the tests, and for this reason these data are not strictly comparable

with those presented in tables 2, 4, and 6. There are so many variables involved in the

manufacture of commercial compounds that

the results in table 1 do not furnish a very satis- factory basis for evaluating the effects of various

ingredients on performance. For this reason

the results on trial mixtures, some of which are described in table 2, are considered to give a more adequate basis for estimating the effect of certain ingredients.

[10]
Figure 5.

Slumping of a calking material from joints between dense bricks {3 and 4) while the same plastic remains

in place between porous bricks {1 and 2).

1. Vehicle

(a) Linseed Oil

Twelve commercial compounds contained

blown linseed oil. Four of these gave satis- factory results in the strain and staining tests, but only one remained as soft as desired in a pat on limestone for 1 year. Samples which

contained polymerized linseed oil were less satisfactory in some of the tests, but their

hardening, as indicated in the last column of

table 1, seemed to be less than for compounds

prepared from blown oil.

Six experimental mixtures were made from

blown linseed oil of viscosities from Zl to Z4,

and four mixtures were made with polymerized

linseed oils of Z3 to Z6 viscosities. All of these

compounds gave satisfactory test results, but

those with polymerized oils hardened less rapidly on limestone than the others. One of the three mixtures made with heavy-bodied

polymerized linseed oil, thinned to lower viscosities with raw soybean oil, was unsatisfactory.

Data on one trial mixture from each group is included in table 4.

[11]
Figure 6.

Amount of slumping in joints of various materials. The compound slumped when placed between steel (1 and 1), steel and marble (1 and 2), marble (2 and 2), and marble and wood (2 and 3). The same compound did not slump when placed between wood (3 and 3), concrete (4 and 4), limestone (6 and 6), and brick (7 and 7). Considerable shrinkage and cracking occurred between the more absorptive materials.

(b) Soybean Oil

The commercial compounds in which treated

soybean oil was the vehicle gave lower strain

values than those containing bodied linseed oil. The correlation between the viscosities of the

extracted oils and the tendency of the compounds to stain marble was better with this

group of samples than with other oils. With

one exception, pats of these compounds on

limestone hardened upon standing in the laboratory.

Six experimental compounds were prepared

from a commercially blown soybean oil of Z6

viscosity. These were entirely unsatisfactory.

Eighteen more were made with blown soybean

oU of Z4 viscosity, and these gave satisfactory

test results. With one exception, they re- mained plastic after 6 months in pats on lime- stone and stayed soft in the container. Penetration tests on two of these compounds showed

an average hardening of 38 percent in 15 days.

Experimental mixtures which used tung oil and

soybean oil, polymerized to viscosities Y, Z2,

Z3, and Z4, were satisfactory except when the

Y viscosity oil was used. These compounds

formed wrinkled skins, but retained their

plasticity in the containers. The penetration

test on these compounds showed an average

hardening of 21 percent in 15 days. Data on

three experimental mixtures with soybean oil as a vehicle are included in table 4.

[12]
Z8

26

Z4

ZZ

ZD

% 16

^ 10

, No. 5

> LEGEND

Shrinkage or? g/ass o

" " sfone X

1 1

1

1

oX

1

1

1

)

1

i

1

1

1 )arnp

20_A: .g-x

1

1

j 5

'OH 0

j /X ^mple No. 4-g -.—^x

' /

lie No:4-q

//^

0

4 8 10 IZ 14 16 18 20 2Z Z4 26 28 30

T/'me in days

Figure 7.

Shrinkage of three commercial samples of calking on glass and limestone for 30 days.

Sample numbers correspond to serial numbers in table 1.

(c) Fish Oil

Blown fish oils were used as a vehicle in 22

of the commercial compounds. Only four of

these failed to give strain-test readings above

0.05 in., but, like most of the compounds,

hardened excessively when pats were left standing on limestone for 1 year. Sixteen experimental compounds were made

from commercially blown fish oils of V, Y, Z,

and Z6 viscosities, but all were unsatisfactory.

The viscosity of the lighter oils was increased

by further blowing, and 36 experimental mixtures made from them. These were satisfactory in the physical tests and had a very slow

rate of hardenmg, for only two became hard

after 1 year on limestone. The viscosity of the

Z6 fish oil was lowered by the addition of other

oils, and 24 experimental compounds prepared.

All were satisfactory in the physical tests and

were still plastic after 9 months on limestone.

Data on six of the experimental mixtures with

fish oil as a vehicle are given in table 4.

[13]
FiGUEE 9.

Effect of width of joint

upon shrinkage and cracking.

Panel of limestone with joints varying from }s in. to y> in. calked with one plastic mixture. Excessive shrinkage and cracking occurred in all joints less than in.

14
1

Table 4.Composition and physical studies on I4. experimental mixtures

Pigment Vehicle Physical tests Observations

Composition Nonvolatile Volatile Stain on " °i

No.

Material Amount Amount Kind

Oil

viscosity

a

3

0

a<

Kind Amount

Strain Li

me

-

stone Marble

Shrinkage Skin at 48 hours

Hardness pats

on

li:

stone

'

E6S

Em

E188

E68 Em

Eli2

MIXTURES CONTAINING FISH OIL

fPrecipitated whiting

I Talc

ILithopone

[Asbestos, 7M

fPrecipitated whiting

Talc Lithopone

Asbestos, 7M

[Asbestos, Fl

[Precipitated whiting

I Asbestine Titantox

[Asbestos, 7D

[Ground limestone. .

.

Talc

[Asbestos, IM

[Chalk whiting

I Talc 1

I Zinc sulfide [Asbestos, J<1 [Precipitated whiting Talc Lithopone

Asbestos, Fl

[Asbestos, 7M

60

[Fish oil blown with small amount of

[ commercial drier.

[Fish oil blown at

I 130° C. 0.05% coI bait added as drier.

[ Varnish 2%.

Fish oil blown at

140° C. 0.1% cobalt and 0.2% lead added

as drier. Blown fish oil (commercial) and boiled

linseed oil (9:1). Blown fish oil (commercial) and raw lin- seed oil (24:1). 0.2% Mn added as drier. Blown fish oil (commercial) and raw lin- seed oil (24:1). 0.05%

cobalt added as drier. Varnish 2%.

%

32

37

}.

33

37 V

29

|z.5 41

NoneMineral

. spirits.

.do_

None.

'Mineral

i spirits.

.dom.

0. 35

.20

.25

.63

OK

OK

OK

OK

OK

OK

OK

OK

OK

ss

OK

OK

Medium

...do.

..do...--

.do_

..do.

SlightSmooth.

do

-do-

[Slightly

I wrinkled.

...do.

Smooth

1 (13)

1 (9)

1 (7)

1 (13)

2(10)

2(10)

MIXTURES CONTAINING SOYBEAN OIL

Elb

Ens

ElSl

{Precipitated whiting

Talc Lithopone

.^.sbestos, 72) {Precipitated whiting

Talc Lithopone

Asbestos, 7H

fPrecipitated whiting. Talc

< Lithopone

.\sbestine lAsDestos, 7M

63

Soybean oil blown at 120°C. 0.01%, cobalt added as drier. Varnish 2%. Soybean oil blown at 140° C, varnish, 2%.

0.08%o cobalt added

as drier. Mixture of soybean and

tung oils (4:1) heated

to 285° C. 0.05% co- balt as drier.

Z2

(Mineral

\ spirits

None.

(Mineral

\ spirits.

0. 20

.22

OK

OK

OK

OK

OK

OK

Medium.

Low.

Medium

.

'Slightly

, wrinkled..

Wrinkled.

Smooth.

1 (9)

1 (7)

1 (6)

MIXTURES CONTAINING PERILLA OIL

[Ground limestone E69 xLithopone

(Asbestos, 7M

iGrouna limestone Lithopone

Talc

Asbestos, 7M

60

30 j-72 103530

30 |70

5

fBlown perilla oil (com-

\ mercial).

[Mixture of blown pe-

< rilla oil (commercial)

I and raw tung oil.

22

|z5 25

(Mineral

[ spirits.

.do...

0. 18 OK OK

5 .26 OK OK

Mediimi

.

-do.

Smooth.

•Slightly

, wrinkled.

3(13)

}2to3(ll)

MIXTURES CONTAINING LINSEED OIL

E137

E1B5

Em

fPrecipitated whiting

.

Talc Lithopone

-Asbestos, Fl

.-\sbestos, 7M

'Precipitated whiting- Talc .-- Lithopone

-Asbestos. Fl

[Asbestos, 7M

Precipitated whiting1 -Asbestine [Lithopone-.- -.- [Asbestos, 7M.

[Mixture of polymer-

{ ized linseed and raw

[ soybean oils (3:1).

f

Polymerized linseed

oil. 0.05% cobalt added as drier. Varnish 2%.

[Linseed oil blown at

I 120° C. 0.24% lead

I and 0.03% mangal nese added as driers.

ZB

ZJ,

46

36

/Mineral

1 spirits.

-do-

-do--.

0.30

.38

OK

OK

OK

OK

OK

OK

Medium

.-do-

-do_--

SmoothfS 1 i g ti 1 1 y 1

1 \ wrinkled. /

^

1 (10)

.do- 1 (7)

" Oii'=satisfactory; SS=slight strain.

^ Numerals signify hardness, namely, l=satisfactory, 2=hard, 3 = very hard,

theses indicate the time (in months) the pats have been on limestone. Two figures, 1-2, signify intermediate hardness. Numbers in paren-
id) Tung Oil

The five commercial compounds which contained timg oil also contained resins and may

be classed as varnish base compounds. These

had good adhesion, remained plastic, and had

excellent workability. A small amount of tung

oil was bodied in the laboratory and used for preparing four experimental compounds. These

were inferior to the commercial compounds,

formed wrinkled skins, and were unsatisfactory

in the physical tests.

(e) Miscellaneous

All of the compounds grouped in table 1 under "Miscellaneous" were unsatisfactory ex- cept 28 A-g, which contained rosm. Seventeen experimental mixtures were made

from commercially blown perilla oil of Z6

viscosity, and seven mixtures were made with

a commercially blown rapeseed oil of the same

viscosity. Although some of these preparations were adhesive enough to pass the strain test,

all but one of them became hard upon standing.

Wlien the viscosity of these two oils was

lowered by the addition of other oils and the

resulting mixtures used to prepare experimental

compounds, the preparations made from blown

perilla oil were slightly better than the six made

from blown rapeseed oil, but all of them hardened too rapidly.

2. Pigments

As shown in table 1, the pigments consisted

of a number of materials, some of which were

finely ground, the others being fibrous. The

fine-ground portion included calcium carbonate

in one of its several forms, talc, quartz, and

diatomaceous silica ; to these lithopone and zinc

oxide were sometimes added to produce lightcolored compounds. The fibrous portion was

generally short fiber asbestos, but cotton fibers were found in two compounds.

Of 11 commercial samples which contained

calcite alone as the pigment, 7 were knife-grade

and 4 were gun-grade. All of the knife-grade

and two gun-grade samples showed poor bonding properties. In the experimental mixtures

it was found that precipitated whiting as the

entire pigment produced compounds that

hardened rapidly and had poor bonding properties, as in the case of tlie commercial samples.

On the other hand, compounds made with other

types of calcium carbonate as the entire pigment, such as chalk whiting or ground limestone, showed fairly good plastic and adhesive

properties when mixed with the proper oils. However, one outstanding property common to

all calking mixtures containing only calcium

carbonate as the pigment was their tendency

to slump. The addition of about 10 percent

of any one of the medium-fine grades of

asbestos {7D, 7K, or 7M) overcame the slumping, hut an equivalent amount of the very fine grades of fiber did not. A pigment which gave good results in

several experimental mixtures was composed

of 50 percent of precipitated whiting, 30 per- cent of talc, 10 percent of lithopone, titanox, or

zinc sulfide, and 10 percent of asbestos.

3. Thinners

The amount of volatile matter in commercial

compounds varied within wide limits. Eleven

samples contained 1 percent or less, one com- poimd 37 percent, and the average of the

entire group was 9.4 percent. Mineral spirits was the most commonly used thinner, although

26 A-k and 26 B-g contained large amounts of kerosene.

The amount of volatile used in experimental

mixtures depended largely on the viscosity of the oil. With viscosities of ZJi., Z5, and Z6, the

volatile A^aried between 5 and 7 percent. Oils

of lower viscosities required less volatile and,

in many cases, thinner was unnecessary.

Wlien higher percentages of volatile were used,

the mixtures showed little or no adhesion, high

shrinkage, and they hardened rapidly.

[16]
Five niixtiires * were made similar in all respects with the exception that the volatile

varied from zero to 16 percent in equal steps.

The various mixtures were placed in }^-in.

joints between slabs of limestone. Cracks

formed in all mixtures with more than 4 percent of volatile. Strain tests and penetration tests were also made on these mixtures at the end of 15 days. The results are shown in

table 5.

Table 5.

Strain and penetration tests

Sample Volatile Strain Penetration

1 Percent

0

4

812

16

Inches

0.26

.23

.03 .02

.02

0.01 cm

>155 no

74

00

2

3

4

5

Of the commercial compounds in table 1 containing more than 15 percent of volatile, only

two remained satisfactorily soft in pats on

limestone for 1 year.

VII. RELATION OF PHYSICAL PROPERTIES TO PERFORMANCE

The period of time during which a calking

compound will serve its purpose depends on the

ability of the compound to retain certain physical properties such as adhesiveness, coliesiveness, and plasticity. Adhesiveness supplies the

necessary bonding property, whereas cohesiveness enables the compound to resist rupture

within itself. The plastic condition depends on

the fluid ingredients in the mixture. Volatile

constituents may soon evaporate, thus causing

shrinkage and stifl'ening of the compound.

Porous materials in contact with the calking

compound may extract some of the nonvolatile

fluid, causing further hardening and shrinkage.

Changes in consistency can be measured as described in section IV, 2 (d) of this report.

Such determinations on commercial materials

have shown that a large change in consistency

occurs within a period of 2 weeks. Observa-

' Base composition as follows:

Oil: Three parts blown fish and 1 part raw tiing heated to 270° C.

(viscosity =Z4).

Pigment: Precipitatccl whiting 60%

Talc 25%

Zinc sulfide 10%

Asbestos 7K. 5%

tions on exposure specimens indicate that this

is a continuous process which may render the

rapidly hardening compoujids useless in less than a year, whereas some remain sufliciently

soft to function for several years. Shrinkage indicates that the conipoiind has

lost a portion of the vehicle. The first manifestation of shrinkage is the formation of con- cave joints or cracks. Some compounds also form voids within the mass, which may be the

result of shrinkage. Regardless of whether

shrinkage is accompanied by hardening, it is undesirable, because it places the joint filler in tension even when there are no structural mo\'ements. Figure 11 shows several rigid joints in which shrinkage has caused cracks. These

usually occur at the sides of joints, but sometimes they form within the compound.

Wlien a joint is in tension, brought about by

shrinkage or a structural movement, the calking should stretch without breaking the bond.

The forces are transmitted to the joint filler by means of its bond; hence the adhesive property

is very important. The most common type of

failure observed in test joints and in buildings was that of ruptured bonds. A satisfactory means of determining the actual bonding

strength of plastic substances has not been

found. The test for bond outlined in section

IV, 2 (b) is not quantitative, but enables one to distinguish between satisfactory and luisatis- factory bonding properties.

The formation of cracks within the plastic

indicates that the cohesive strength is less than

the bonding strength. Mixtures of high-volatile content are apt to become somewhat brittle or deficient in cohesive strength after a short

time. The test for tenacity described in sec- tion IV, 2 (c) aft'ords a means of determining

this property.

The density of proprietary compomids varies

from about 1.3 to 2.5 (10.8 to 20.8 lb to the gal).

Since the density of the materials composing

various products does not vary greatly, it seems logical to believe that those of low

weight contain more entrapped air than the

heavy compositions. If this is true, a lowdensity product may be expected to harden more rapidly than one of high density, provided

the oil contents of the two axe identical, because

the entrapped air will cause some oxidation of

[17]
the oils within the mass. A high-density com- pound is more apt to flow or shmap in the joints

than a low-density material of the same consistency. Therefore, the high-density material

must be made somewhat stifter to overcome

slumping, and this may add materially to the

cost of application. Since the data obtained

in the shrinkage test enables one to compute

the density, this should be done for additional

information.

VIII. PRIMERS AND THEIR EFFECTIVENESS

Various types of primers are used with plastic

calking materials. They are intended to seal the pores of the masonry or other building material with which the calking compound is to be

placed in contact. Shellac is one of the com- mon primers; but thinned oils, thinned varnish,

aluminum soap solutions, and waterglass are

also used. It seems to be a common practice

to coat the sides of joints with the primer and

then insert the calking without allowing a suffi- cient time for the priming solution to dry. It is doubtful if any primer will seal the pores

effectively if the primer is not allowed to dry.

If the plastic is applied to joints treated with

shellac or waterglass before the latter are dry.

the bond may be adversely aft'ected. The drying time of any primer is affected somewhat by

the type of surface to which it is applied.

Workmen claim an additional advantages for primers in that they "lay the dust" in joints

and thus permit a better bond to be obtained.

Dust interferes with bonding, but it can

probably be removed at less cost by other means.

Studies were made on 11 commercial primers

by applying them to limestone 24 hr before the

calking materials were applied. Shrinkage,

tenacity, and bond determinations were made

on the calking materials after 60 days and compared with those from similar tests in which no

primer was used. The results are given in

table 6. Five brands of calking with volatile

contents from approximately 8 to 22 percent were used in these tests. The slight reductions in shrinkage caused by

various primers cast considerable doubt on

their value for improving the performance of calking materials. This is especially true when the calking compound has a high volatile content. In some cases the bond and tenacity were affected adversely. Primers which materially reduced the shrinkage without seriously

affecting the other properties were thinned

oils, thinned varnishes, and tung-oil paint.

Table 6.

Results of tests with calking materials on stone primed with various commercial primers in comparison with

the same calking on unprimed stone

Primer

used on

stone surface 2

Calking samples i

7S A-g (7.8%) 16A-g (21.9%) U A-g (8.8%) U D-g*

(12.0%)

5703 (8.7%,)

Shrinkage

None

a

b

ci

e/._... g

h

i

3k

Tenacity 3

OK

OK

OK

OK

FOK

OK

OK

OK

OK

OK

OK

Bond ' ShrinkOK

OK

FOK

FOK

OK

OK

OK

OK

OK

OK

Tenacity 3 Bond < ShrinkOK

OK

FOK

FOK

OK

OK

OK

OK

OK

OK

Tenacity 3

OK

OK

OK

OK

OK

OK

OK

OK

OK

OK

OK

OK

Bond ' Shrink- ShrinkOK

OK

OK

OK

FOK

OK

OK

OK

F

FOK

Tenacity 3

OK

FOK

OK

FOK

OK

OK

FFOK

OK

Bond

OK

OK

F

FOK

OK

OK

OK

OK

OK

OK

OK

> Serial numbers in table 1 with percentage volatile (weight loss in 60 days) in parentheses. Sample 5703 is not listed in table 1.

2 Primers a, b, and a are essentially aluminum-soap solutions. Primers g, i, and ; are thinned oils containing aluminum soap. Primers e. /, and A are thinned varnishes. Primers c and k are shellac and tung-oil paint, respectively.

3 F signifies failure; OJsT, satisfactory.

* Tenacity and bond were not determined for this sample. The test had not been developed at the time these measurements were made.

[18]
—

H

[ gum.

-

Figure 10.

Effect of priming upon staining property of calking compounds.

I'anel of limestoue in which the joints were primed for half of the length (right half) and the other half left unprimed, then all filled with a call<int; mixture of pronounced staining quality. Primers used were water-siass (top), thinned oil (middle), and shellac (bottom). The results shown in figure 10 indicate that

the performance of a staining compound can

be improved somewhat by priming, but that

primers do not entirely prevent the absorption

of oil or the formation of cracks. A point that

should be considered is the durability of the

primer. Solutions of waterglass (silicate of soda) tend to decompose, on drying and

exposure to the air, into silica (more or less hydrated) and sodium carbonate; the silica layer on the masonry may reduce the bond

between the calking compound and the masonry

and the sodium carbonate may saponify some

of the oil in the compound. Shellac is not very

durable when exposed to the weather, and

there is not much protection to it in a calked

joint on the outside of a building. However, it has some desirable features for this purpose in

that it dries quickly and forms a film that is temporarily almost impermeable. In general,

primers may be considered of value only in preventing or reducing the absorption of oil by

porous materials. They do not prevent shrinkage caused by volatile matter in the calking;

hence a nonstaining compound cannot be

expected to serve its purpose any better in

primed joints than in unprimed joints.

IX. DURABILITY

The weathering and aging effects were studied

by means of exposure tests on the roof of a

building and inspection of actual installations.

The indications are that oil mastics do not

usually deteriorate by crumbling, as do some

masonry mortars, but fail by gradual hardening, bond rupture, or cracldng within the compound. Those materials which contain an

excess of pigment often form a network of fine cracks and become almost as hard as mortar.

Such compounds would probably disintegrate

after a period of years, but they fail to function

as plastic joint fillers in a much shorter time.

In the exposure tests, brittle films formed on

the surface of a few specimens, which finally

broke and scaled oft".

1. Exposure of Strain-Test Specimens

One series of exposure tests consisted of joints between slabs of limestone, slate, and

marble and also between five grades of brick.

These accessory materials were chosen for a

large range in porosity, the percentage of water

absorption being approximately as follows:

Limestone, 5; slate, 0.35; marble, 0.16; and

the bricks ranged from 1 to 12. Seventeen

commercial brands of calking materials made

by the larger producers were used. The types

of oil used in these compounds were not Imown.

All were gun grade except two. The volatile

varied from 1 to 14 percent and pigment from

46 to 85 percent. Six compounds contained

whiting in amounts varying from 2 to 79 per- cent of the total pigment, and seven compounds

contained rosin. Several joints between lime- stone slabs were made with each brand of

calking material.

[19]
Strain tests were made on the limestone

specimens after aging, as follows: first set cured

for 30 days indoors; second set exposed to the

weather for 30 days; third set exposed to the

weather for 1 year. There was no appreciable

difference in the results for specimens cured

indoors 30 days and those exposed to the

weather for 30 days.

Joints made from two brands of calking

showed no retrogression after 1 year's exposure,

but the other samples showed decreases in strain values ranging from 12 to 100 percent

and averaging 60 percent. Joints in the very

dense materials (marble and slate) for most

tests gave higher strain values than the joints

in limestone. However, the results on joints

between the dense brick were usually not as high as for joints between more porous grades.

Since the removal of vehicle from the plastic

may seriously affect durability, the lower strain

value with the dense brick seems to indicate

that the capillarity of these was greater than

for the more porous grades. Very dense

materials like marble probably exert a strong

capillarity, since they often show oil penetrations extending an inch or more away from

the joints. However, the amount of oil re- moved from the plastic in producing such stains

is small, because the total porosity of the marble is very low.

Observations on the specimens that had been

exposed to the weather for 1 year gave some

indications of the causes of deterioration. In

several specimens the plastics had started to separate at the sides of joints on account of

shrinkage and poor bond. Decreases in strain

values on aging may indicate that the materials

have hardened excessively or that the bonding

value has retrogressed.

2. Exposure of Rigid Joints

Seventeen brands of calking materials in grooved blocks of limestone have been studied

after exposure to the weather for periods varying from 2 to 8 years. The stone blocks measured 4 by 4 by 2}^ in. with two grooves % in. wide and % in. deep. Both grooves in each were filled with one sample of calking, the only

difference being that one groove was primed

and the other imprimed. Some brands of

calking in the exposures were represented by more than 100 specimens. The inspection of these specimens consisted in rating them as to tightness of the joints, consistency of the

calking, and general appearance.

Most brands showed large differences in results for different samples. This may be

partly accounted for by the fact that some

manufacturers produce compounds of several

different compositions. However, there are

also marked variations in the products of manufacturers who apparently use only one formula.

For instance, a firm which evidently uses 1 formula has 75 specimens in these tests. There

are 21 specimens in the group that have been

exposed for an average of 7 years, and 15 of them were judged to be in a passable condition.

In the group exposed for an average of 3 years

there were 17 specimens, and only 7 of them

were rated as passable. Similar variations occur in most other brands, as illustrated in figure 11. A few specimens of various products were found to be in good condition after exposure

for 6 or 8 years. The composition of the calking materials used in these tests was not determined, and hence it is not possible to draw any

definite conclusions regarding the efl^ects of various ingredients on durability. Conclusions based on the assumption that any brand was made according to a single formula over a period of years are of doubtful value. The

tests give indications that it is possible to make

a plastic calking compound that will give satis- factory service for more than 8 years, but for consistently satisfactory performance it may

be necessary for some producers to control the

fabrication process more carefully.

One conclusion that seems to be justified by

these tests is that coloring pigments are detri- mental to durability. All specimens in which

the calking was white or blue in color were

very hard and showed a network of fine cracks.

3. Inspection of Buildings

Inspections were made of calking materials

in 33 structures located in 18 cities, the farthest

south being Galveston, Tex., the most northerly

being Willianisport, Pa. The brands of calking were known for most of these and 15 dift'erent

[20]
Figure 11.

Rigid joints in limestone after exposure to the weather. Two specimens of each brand were sslected from a large number to represent the best results (left) and the poorest (right) for each of 12 products. The numbers above each group signify the same brands as in table 1.

products were represented, but no specific

information regarding tlieir composition was

available. The plastics were in contact with

various materials, such as granite, marble,

limestone, brick, mortar, steel, bronze, and

wood.

The observations on actual installations agree, in general, with laboratory results and

observations on exposure specimens in that the

plastics bond somewhat better to porous materials than to nonporous materials or to materials of very low porosity. Plastic joints

between brick and steel were noted where

excessive shrinkage had caused the calking

compound to separate from the steel. An

instance of slumping, as in figure 6, was found

where a gun-grade calking material was used

between marble and metal. Excessive hardening of the plastics in marble construction was noted where sufficient coloring pigment had

been used in the compounds to produce very

light colors. In several cases it appeared that

the calking was less durable in contact with

mortar than where it was in contact with stone. The calking in one case where it was used

between sheets of lead had failed completely.

[21]
The installations examined were from 2 to 8

years old and in about 50 percent of these the

calking appeared to be in good condition,

whereas that in about 20 percent was poor. These observations indicate that calking compounds can be made which will give good service

for more than 6 years. No definite differences

in performance could be attributed to dift'erent climatic conditions.

X. SUMMARY

Seventy-two commercial brands of plastic

calking compounds were examined by chemical

and microscopic methods, and the effects of

different treatments of oils in numerous trial mixtures were studied by means of certain

laboratory tests. The compounds were studied (1) by laboratory tests simulating the conditions of service,

(2) by exposure tests, and (3) by inspection of several structures showing the materials in use for periods up to 8 years. New tests have been devised which are simpler than the tests now in use, and the

properties so determined are thought to give more specific information on quality.

Certain conditions affecting the durability

and performance have been given attention. In this connection various types of primers

have been tested to determine their effects on

shrinkage, bond, and tenacity of the plastic

calking compounds. The performance of these

products on various types of building materials

with particular reference to porosity and

capillarity has been studied. Although the

work has not been completed, the followingstatements seem to be justified:

1. A considerable variety of ingredients can

be utilized in the plastic calking compounds

with good results. For the vehicle certain

blown oils such as soybean, cottonseed, linseed,

and fish seem to give the most satisfactory

results. When mixed with properly treated

oils, the pigments may consist of any of the

common fillers, such as calcite, talc, asbestine,

etc., with asbestos fibers. These can be used in almost any proportions provided that not less than 5 percent is fiber of a suitable grade.

Coloring pigments—such as lithopone, zinc

oxide, or titanox—should be limited to amounts

that will not cause the compound to craze or harden too rapidly. Volatile thinner in the

vehicle causes shrinkage of the compound and

if used in excessive amounts, "bleeding,"

premature hardening, or loss of tenacity may

occur.

2. Physical qualities desired are low shrinkage, low rate of hardening, tenacity, adhesiveness, and ability to retain the vehicle; also, the

consistency should be such that the compound

will work easily but not flow, after placing in the joints. The formation of a skin within 3 days after placing in the joints is desirable.

3. Hardening of the plastics reduces their

ability to function under service conditions and

caxises higher bonding stresses when the joint

is in tension. The average rate of hardening of 93 samples of proprietary compounds was 55

percent, the maximum being 87 percent and the

minimum 15 percent. Since the value of a calking compound depends on its remaining soft,

the rate-of-hardening test is believed to be a good indication of durability.

4. Shrinkage is caused mainly by evaporation

of volatile matter and absorption of a part of the vehicle by porous materials in contact with

the calking. In the usual commercial compounds, shrinkage continues over several

months and sometimes amounts to more than

25 percent of the original volume. The first manifestation of shrinkage of calking compounds is the formation of concave joints or

cracks. Excessive shrinkage causes separation

from the sides of joints or, in materials of poor

tenacity, the formation of cracks within the

plastic. The average shrinkage of trade products for 15 days in contact with limestone was, for 104 gun-grade materials, 22 percent;

and for 26 knife-grade materials, 8 percent.

Since shrinkage causes strains in the calking

sufficient, in many cases, to cause bond failures

regardless of structural movements, it seems

evident that a low limit for shrinkage should be

a requirement.

5. The adhesion or bonding value of plastics

varies appreciably with the type of adjacent

material, that is, they bond more satisfactorily to porous materials than to materials of low

porosity. The value of the compound in this respect seems to depend to some extent upon

the type of pigment (filler) used.

[22]
6. The consistency required for different in- stallations may vary somewhat with such

considerations as joint widths, the type of material in contact with the calking, and the

temperature at the time of application. If the calking does not sag or flow withm a few

hours after the joints are filled, sagging is not

apt to occur later. Troubles of this kind are more frequent in joints between nonabsorptive

materials than in joints between absorptive

materials. The addition of thinner, as sometimes practiced at the building site to make

compounds more workable, is apt to cause

undesirable results. For cold-weather application the producers recommend softening the

calking by setting the container in hot water.

7. Staining of porous materials by plastic

calking indicates that oils were of too low

viscosity or that too much thinner was used in the compound. Stainmg of masonry materials

by the calking is objectionable in two ways:

(1) The appearance of the masonry is unpaired.

(2) If appreciable amounts of oil are removed

from the calking, shrinkage and hardening

result. OH stains in materials havmg a porosity

of 10 percent or more usually disappear after a few months of weathering, but in denser materials they disappear very slowly.

8. The density of commercial calking mixtures varies from 1.3 to 2.5 (10.8 to 20.8 lb per

gal). The lighter mixtures probably contain a

considerable amount of entrapped air which may

increase the shrinkage and rate of hardening.

9. Priming the surfaces of porous materials

before placing the calking may reduce staining

and adversely aft'ect bond and tenacity. When

primers are used, they should be allowed to dry

before the calking is applied. Tests on various

primers indicate that thinned varnishes and

thinned oils are the most satisfactory types.

10. Inspection of masonry structures and

exposure specimens indicates that it is possible

to make calking compounds that wiU last for at least 8 years. Studies on specimen joints that

have been exposed to the weather for several

years indicate that each of the trade preparations varied in quality, resulting in large dift'er- ences in dui'ability.

Washington, July 21, 1939.

[23]


r Ii i I
BUILDING MATERIALS AND STRUCTURES REPORTS

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BMSl Research on Building Materials and Structures for Use in Low-Cost Housing lOi: BMS2 Methods of Determining the Structural Properties of Low-Cost House Constructions. _ 10^ BMS3 Suitability of Fiber Insulating Lath as a Plaster Base 10^ BMS4 Accelerated Aging of Fiber Building Boards 10^ BMS5 Structural Properties of Six Masonry Wall Constructions 15^ BMS6 Survey of Roofing Materials in the Southeastern States 15^ BMS7 Water Permeability of Masonry Walls lOji BMS8 Methods of Investigation of Surface Treatment for Corrosion Protection of Steel 10^ BMS9 Structural Properties of the Insulated Steel Construction Company's "Frameless-Steel"

Constructions for Walls, Partitions, Floors, and Roofs lOf BMSIO Structural Properties of One of the "Keystone Beam Steel Floor" Constructions Sponsored by the H. H. Robertson Company lOp

BMSll Structural Properties of the Curren Fabrihome Corporation's "Fabrihome" Constructions for Walls and Partitions 10^ BMS12 Structural Properties of "Steelox" Constructions for Walls, Partitions, Floors, and Roofs

Sponsored by Steel Buildings, Inc 15j^ BMS13 Properties of Some Fiber Building Boards of Current Manufacture 10^ BMS14 Indentation and Recovery of Low-Cost Floor Coverings lOi BMS15 Structural Properties of "Wheeling Long-Span Steel Floor" Construction Sponsored by

the Wheeling Corrugating Co lOji BMS16 Structural Properties of a "Tilecrete" Floor Construction Sponsored by Tilecrete Floors, Inc lOfi BMS17 Sound Insulation of Wall and Floor Constructions lOp

BMS18 Structural Properties of "Pre-Fab" Constructions for Walls, Partitions, and Floors Sponsored by the Harnischfeger Corporation lOp

BMS19 Preparation and Revision of Building Codes 15p

BMS20 Structural Properties of "Twachtman" Constructions for Walls and Floors Sponsored by

Connecticut Pre-Cast Buildings Corporation 10(6 BMS21 Structural Properties of a Concrete-Block Cavity-Wall Construction Sponsored by the National Concrete Masonry Association 10^ BMS22 Structural Properties of "Dun-Ti-Stone" Wall Construction Sponsored by the W. E. Dunn Manufacturing Co 10(4 BMS23 Structural Properties of a Brick Cavity-Wall Construction Sponsored by the Brick Manufacturers' Association of New York, Inc 10^ BMS24 Structural Properties of a Reinforced-Brick Wall Construction and a Brick-Tile CavityWall Construction Sponsored by the Structural Clay Products Institute 10^ BMS25 Structural Properties of Conventional Wood-Frame Constructions for Walls, Partitions,

Floors, and Roofs 15^ BMS26 Structural Properties of "Nelson Pre-Cast Concrete Foundation" Wall Constructions

Sponsored by the Nelson Cement Stone Co., Inc lOfi BMS27 Structural Properties of "Bender Steel Home" Wall Construction Sponsored bv The

Bender Body Co lOfi BMS28 Backflow Prevention in Over-Rim Water Supplies 10^ BMS29 Survey of Roofing Materials in the Northeastern States.: 10(4 BMS30 Structural Properties of a Wood-Frame Wall Construction Sponsored by the Douglas

Fir Plywood Association - 10(4 BMS31 Structural Properties of "Insulite" Wall and "Insulite" Partition Constructions Sponsored by the Insulite Co 15^ BMS32 Structural Properties of Two Brick-Concrete-Block Wall Constructions and a Concrete- Block Wall Construction Sponsored by the National Concrete Masonrv Association. 10^ BMS33 Plastic Calking Materials '. 10^