Nationei Bureau of Star.caids

Library, N. W. Bldg.

AUG 1 9 1952

S6

Methods and Equipment for Testing

Printed-Enamel Felt-Base Floor Covering

United States Department of Commerce

National Bureau of Standards

Building Materials and Structures Report 130
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[List continued on cover page in]
UNITED STATES DEPARTMENT OF COMMERCE . Charles Sawyer, Secretary NATIONAL BUREAU OF STANDARDS • A. V. Astin, Aclinf, Director

Methods and Equipment for Testing

Printed-Enamel Felt-Base Floor Covering

George G. Richev, Elizabeth H. McKenna, and Robert B. Hobbs

Building Materials and Structures Report 130

Issued May 1, 1952

For sale by the Superintendent of Documents, U. S. Government Printing Office, Washington 25, D. C.

Price IS cents
Foreword

Print ed-enamel felt-base floor coverings form the largest class of resilient non-textile floor coverings, which include linoleum, rubber tile, asphalt tile, and plastic tile and sheeting. The annual production of printed-enamel

floor coverings, known in the trade as "felt-base rugs", amounts to more than

200 million square yards, valued at over 80 million dollars at the factory.

Despite this large volume of production, no generally accepted methods for the evaluation of the properties of this material have been established. This

paper describes methods and equipment for measuring the Aveight, over-all

thickness, thickness of enamel and of seal coat, resistance to scrubbing with

cleaning compound, resistance to kerosine, flexibility, and tearing strength.

The results of laboratory tests are correlated with results of service tests of

eleven proprietary products. The correlation was significant for all properties

studied except thickness of seal coat, but no single property was outstanding

in its level of significance. Thus it appears that these tests will be useful for manufacturers, purchasers of large quantities, and others interested in evaluating printed-enamel felt-base floor coverings.

A. V. Astin, Acting Director.

Contents

Page Foreword ii 1. Introduction 1

2. Materials tested . 1

3. Test methods and equipment 2

3.1. Atmospheric conditions 2

3.2. Weight . __i 2

3.3. Flexibility 1 2

3.4. Tear resistance 2

3.5. Thicknesses of the seal coat and of the enamel coat 3

3.6. Over-all thickness 3

3.7. Resistance to cleaning compound 3

3.8. Resistance to kerosine 4

4. Service tests 4

4.1. Test of materials laid in corridor 4

4.2. Test of materials laid on stairway 5

5. Results of tests 5

5.1. Correlation of results of laboratory and service tests 5

5.2. Measurements of weight and thickness 8

5.3. Flexibility..- . 8

5.4. Tearing strength 9

5.5. Resistance to cleaning compound 9

5.6. Resistance to kerosine :__ 9

5.7. Service tests 9
Methods and Equipment for Testing Printed-Enamel

Felt-Base Floor Covering

George G. Richey, Elizabeth H. McKenna, and Robert B. Hobbs

This paper describes methods and equipment for measuring the weight, over-all thickness, thickness of enamel and of seal coat, resistance to scrubbing with cleaning compound, resist- ance to kerosine, flexibility, and tearing strength of printed-enamel felt-base floor covering. Results of laboratory tests are correlated with results of service tests of 11 proprietary

products. The correlation was significant for all properties studied except thickness of

seal, coat, but no single property was outstanding in its level of significance.

1. Introduction

Procedures for the evaluation of the properties

of some nontextile floor coverings, such as linoleum,

rubber tile, and asphalt tile, have been established

for many years. These methods and the equipment associated with them have been accepted

generally by consumers and manufacturers.

Printed-enamel felt-base floor covering attains an

annual volume of production amounting to 200

million square yards, valued at 80 million dollars at the factory, according to the 1947 Census of

Alanufactures. Although this volume of production exceeds that of any other type of nontextile

floor covering, no generally accepted methods of

tests have been established for the evaluation of

the properties of printed-enamel felt-base floor coverings.

The purpose of this investigation was to develop

such methods of laboratory tests, and to correlate

the results of laboratory tests with the behavior of the material in actual service, insofar as

practicable.

The methods reported here are suitable for the

evaluation of the following properties: Weight,

flexibility, tear resistance, thickness of enamel

coating, over-all thickness, resistance to cleaning

compounds, and resistance to kerosine. These

methods and the results given in this paper may

also be employed in the development of improvements in this type of floor covering.

2. Materials Tested

Eleven samples of printed-enamel felt-base floor covering purchased on the open market from retail outlets in Washington, D. C, were included

in this investigation. They represented all available grades from all the manufacturers whose

products were obtainable at retail at the time.

The samples included materials from all price ranges. Each floor covering consisted of a prepared felt backing to one side of which was applied an enamel

coating, which constituted the wearing surface.

The under side of the felt was painted. Microscopic examination of sections cut from the floor coverings showed, on all except one, that a paint

coating had also been applied on the upper side of

the felt backing before application of the enamel

coat. Descriptions of the materials are given

in table 1.

Table 1. Manufacturer, size, and other identification of printed-enamel felt-base floor coverings tested

Designation Manufacturer Size Form Other identification by

manufacturer Description of color and pattern

C-L.

C-2_.

C-3_.

C-4_.

C-5_.

C-6.

C-7_.

C-8_.

C-9_. C-10

C-ll

W

x

YX

z

ft. 9 x 12

12 x 12

12 x 12

9 x 12 9x12

9 x 12 9x 126

9 x 12 9x12

9 x 12

Rug

..do.

_.do.

__do. -do_

.do.

.doRoll. Rug.

.do.

.doDeluxe, heavy weight.

Standard, secondStandard, regular- Deluxe

_do-

_ do- None—

.

do_

do.

First grade- None

Leaf pattern in various shades of red with slight amounts of green, yellow, and black. Gray, black, blue, and red tile pattern on ivory background.

Light tan, black, blue, and red tile pattern on ivory background. Tan and brown dot pattern with some red and black and scattered blocks of green, yellow, black, and red on cream background.

Tile pattern in various shades of gray with contrasting gray dots; a few solid blocks of yellow, blue, red, and green on ivory back- ground.

Floral pattern in blue, green, brown, tan, and orange on back- ground of two shades of red. Tile pattern in gray, black, ivory, red, and tan. Block pattern in gray, red, and black on ivory background.

Floral pattern in various shades of red with green, yellow, brown, and red on a background predominately tan and gray. Leaf pattern in tan and brown shades, with slight amounts of red, orange, ivory, and green on chocolate background.

Floral pattern in black, white, and tan with slight amount of green on red background.

985468—52 1
3. Test Methods and Equipment

3.1. Atmospheric Conditions

Measurements of all properties were made with

specimens conditioned in an atmosphere of 65 ±2

percent relative humidity at a temperature of 70°

±2° F for at least 48 hr. The specimens were

also tested under these atmospheric conditions.

These conditions were adopted simply because

they were the ones most conveniently available at the time the tests were made. There seems to be no reason to prefer them over the present standard

conditions of 73° F and 50-percent relative

humidity.

3.2. Weight

The weight of each floor covering was obtained

by weighing and measuring specimens approximately 4 by 4 in. in size cut from the full thickness

of the material. Weighings were made to the nearest gram, and lineal dimensions were measured

to the nearest 0.02 in. From the weight and measurements so obtained, using three specimens, the

average weight per square yard was calculated.

3.3. Flexibility

Specimens, each 2 by 8 in., were cut longitudinally and transversely from each of the floor coverings, then bent over a series of mandrels of

decreasing size, ranging in diameter from 4 to 1 in., by increments of }i in. , until cracking of the enamel

coating was observed. Each strip was bent at its center over the mandrel, with the felt backing on

the inside, through an arc of 180° in approximately

5 sec. and at approximately a uniform speed. Two

specimens were tested from each of the floor coverings.

3.4. Tear Resistance

In the study of tear resistance, the Elmendorf

tear tester modified to double its capacity, as described by Carson and Snyder, 1 was used. The

method of operation of the tester was similar to that described in the ASTM test for tearing resist- ance of paper,2 except for the number, size, and

shape of specimens used. This method deter1 F. T. Carson and L. W. Snyder, Paper Trade J. 86, 13 (1928).

2 ASTM Designation D689-44, ASTM Standards,.Part III-B (1946).

Figure 1. Dimensions of specimen for test of tear resistance.

mines the average force, in grams, required to tear a single rectangular specimen by measuring the

work done in tearing the specimen through a fixed

distance. The scale of the tester is graduated to indicate the ratio of the work done (in gramcentimeters) in tearing the specimen to the total tearing length of 16 sheets. This total tearing

length is 16 times 4.3 cm times 2, that is, 137.6 cm. The factor 2 is included because, in order to tear a sheet through a given distance, the tearing force,

must be exerted through twice that distance.

Preliminary tests were made to compare, with

the rectangular specimen, one having a semicircular shape, with a radius of 38 mm, above the top

of the initial slit. The dimensions of the specimen

are shown in figure 1

.

For the rectangular specimen, the length of tear was 43 mm. As the capacity of the instrument was doubled, the indicated scale readings were

multiplied by the factor 16X2 to obtain the

average tearing force in grams.

For the specimen with the semicircular area, the

radius of curvature, 38 mm, was equal to the length

of tear. Hence, the indicated scale readings were

multiplied by the factor (16X2X4.3)/3.8, that is, 36.2, to obtain the average tearing force for the

specimen.

The residts of comparative tests on the two

shapes of specimens for two varieties of floor cover- ing are given in table 2. Each mean represents

eight determinations. The variability for the

rectangular specimens is much greater than for

those with the semicircular area. For this reason, further tests on all the floor coverings were made

with the semicircular specimens.

Table 2. Tearing strength, in grams, of rectangular and semicircular specimens

Sample

Rectangular specimen Semicircular specimen

Machine direction Cross-machine

direction Machine direction Cross-machine

direction

Mean Std. dev. Mean Std. dev. Mean Std. dev. Mean Std. dev.

C-5

C-6._

954

965

6446 1,274 1,356

130

144 915

898 40

22 1,1701,025

79

83

2
In making subsequent tests, five specimens

were cut from each of the two principal directions

of the floor covering and tested. The indicated

scale reading was multiplied by the factor 36.2 to obtain the tearing force in grams. This value was rounded off to the nearest 10, and in the

mean of the five determinations for each direction was recorded.

3.5. Thicknesses of the Seal Coat and of the

Enamel Coat

Thicknesses of the seal coat and the enamel

coat were determined by observation with a measuring microscope on sections cut at a right angle

to the surface of the floor covering. The equipment used was capable of making measurements

accurate to 0.0005 in. The arithmetic mean of 10 measurements was taken as the thickness of

the seal coat. The arithmetic mean of 10 measurements of sections comprising at least three

different colors of the pattern was taken as the

thickness of the enamel.

3.6. Over-all Thickness

The over-all thickness of the floor covering

under a load of 3.0 ±0.1 oz exerted by a weight

through a flat contact foot 0.25 ±0.01 in. in diameter was determined by means of a dial micrometer. Measurements were made to the nearest

0.001 in. The arithmetic mean of five measure- ments was taken as the over-all thickness of the

material.

3.7. Resistance to Cleaning Compound

The resistance of the enamel coating to scrubbing

with an alkaline soap solution was determined

with a modified Schiefer abrasion machine.3 This

apparatus was modified to use a nylon bristle

brush as the abradant, and to accommodate a brass

cup to retain the test specimen and the solution.

Figure 2 shows the brush, cup, and specimen in

position on the machine.

The brush, shown schematically in figure 3, was made from a commercial article by sawing it in

half transversely and cutting the slots by which the

brush is engaged in the holder. Each tuft consists

of 34 nylon bristles, each 0.014 in. in diameter, and

the backing is of polymethyl methacrylate. The

bristles were worn to a uniform length before use by rotating the brush 1,000 times in the Schiefer machine against B-A flint paper 1/0, with a load

of 4.14 lb. In order to keep the solution distributed over the surface of the specimen during operation of the machine, a distributor plate of

acrylic plastic, % in. wide, was fixed along a

radius of the cup, so as to just clear the surface of

the specimen and the side of the cup. The total

load on the brush was 4.14 lb. The solution used for the test contained 0.5

percent of soap, conforming to the Federal Specification for chip soap,

4 and 0.5 percent of chemically pure sodium carbonate. It had a pH of

about 10.6. In order to simulate more closely the conditions

of scrubbing in actual service, the temperature of

the solution was maintained at 45° ±2° C during

the test. This was accomplished by keeping the

entire apparatus in a heated enclosure, with the

temperature of the solution being measured by a thermocouple immersed in it. The test specimen was cut with a circular steel die having a diameter of 4

X %2 in. It was placed

in position and the cup was attached. Approximately 50 ml of the solution, previously warmed

to 50° C, was placed in the cup. The machine was then operated for 9,000 revolutions of the

specimen against the brush. The specimen was

removed, rinsed with tap water, allowed to dry at room temperature, and the area of seal coat or

felt exposed was measured to the nearest 0.01 in.2 with a planimeter. The areas in square inches

exposed on five test specimens from each material

4 Federal Specification P-S-566a for Soap; Chips.

Figure 2. Schiefer abrasion machine with cup and brush

for measuring resistance to cleaning compound.

I » I ' t I l » c

'it

Mil 1

II

II

3"

8

3 Herbert F. Schiefer, Lawrence E. Crean, and John F. Krasny. J. Research NBS 42, 481 (1949) RP1988. Figure 3. Brush used with Schiefer abrasion machine.

3
were added, and the result taken as the effect of

scrubbing with the cleaning compound.

In order to study the effect of variations between the brushes on the results of this test, a comparison was made of one brush that had been

used for tests of 70 specimens (600,000 rotations

in the Schiefer abrasion machine, representing

approximately 40 hr of service in the machine)

and three new brushes. Twelve strips were cut

at random from sample C-5, and four test speci- mens were cut from each strip. A specimen from

each strip was tested with each brush. The test procedure was identical with that described previously. A statistical analysis of the results

showed there were no significant differences in the results obtained with the used brush in comparison with the new brushes, and there were no

significant differences in the effects produced by

the three new brushes in comparison with each

other. The tabulation of this analysis is given

in table 3. Table 3. Analysis of variance of effect of cleaning com- pound on sample C—5, using an old brush and three new

brushes

Source of variation Degrees

of freedom Sum of squares Mean square

Between means of strips Between means of brushes

Interaction

11

333

2. 1460

0. 1960

2. 5774

0. 1951 .0653

.0781

Total 47 4. 9194 0. 1047

In a few instances it was necessary to add about

10 ml of solution during the test because of losses from evaporation, leakage, and absorption of solution by the specimen. Test specimens from two

of the floor coverings were run for less than the

prescribed 9,000 rotations because the enamel

coating was removed relatively rapidly from both

of these materials.

3.8. Resistance to Kerosine

A metal ring of approximately 4 in. inside diameter was cemented to the enameled surface of

floor covering by means of cellulose nitrate

adhesive. The adhesive was applied on the outer

surface of the ring and the floor covering. Care was taken to prevent any of this adhesive from

getting on the test area enclosed by the ring.

After a 24-hr drying period (minimum), 25 ml

of kerosine was placed on the test area, and this expose was allowed to continue for 72 hr. At the

end of this period the kerosine was removed, the

test area was rinsed with tap water, and any

blistering of the enamel noted.

4.1.

4. Service Tests

Test of Materials Laid in Corridor

The corridor connecting the second floors of the

Munitions Building and the Navy Department

Building in Washington, D. C. was selected for

this installation. This corridor is about 100 ft long and 7% ft wide, with no doors except those

at each end. The existing tongued-and-grooved

wood floor in the corridor was repaired and the

entire area was sanded to remove high spots.

Each specimen installed was approximately 60

in. long and 84 in. wide, placed so that its greater

dimension extended across the width of the corridor. The specimens were separated from each

other by means of 1-in. strips of floor covering,

nailed to the wood floor. A clearance of % in. was allowed between the edge of the specimen and

the adjacent edge of the strip. These strips

served as furring under strips of galvanized sheet

metal 3 in. in width, which were used to cover the

edges of adjacent specimens. The sheet-metal

strips were nailed to the wood floor through the

furring strips. By this method of installation

linear dimensional changes of the floor coverings

could occur without causing buckling of the speci- mens. The test installation was opened to traffic in February 1947. The specimens were mopped

twice each week with water to which 2 percent

(by weight) of cleaning compound was added.

The analysis of the cleaning compound used is given in table 4.

Table 4. Analyses of cleaning compounds used in service

tests

Property

Matter volatile at 105° C

Neutral inorganic salts Sodium chloride (NaCl)

Free alkali (NaOH)

Rosin, sugar, etc Anhydrous soap

Synthetic detergent

Insoluble siliceous material

.

Alkaline salts (Na2COs)

Total.

Munitions

Building

installation

3%

59% 1%

None

do None detected. 37%

100%.

National Bureau of Standards

installation

10%

None

Do.

1456%

20%

100%

After approximately 12 months of service, 14

observers rated the specimens in comparison with

each other, on the basis of distinctness of pattern,

gloss, resistance to soiling, and general appearance.

These observers included scientific personnel of

the National Bureau of Standards, representatives

of manufacturers of printed-enamel felt-base floor covering, and consumers. A relative rating of

A, B, C, or D, was assigned to each specimen by

each observer. An 'A" rating indicated the best

floor coverings, and "B", "C", or "D" ratings

progressively poorer materials. These ratings were then tabulated.

Numerical values of service ratings were obtained on the basis that each observer had an

equal number of total points to assign (a total of

50 points was arbitrarily selected). In addition,

ratings of A, B, C, and D were credited in the

proportion of 4:3:2:1, respectively, for every

observer. By this method the over-all influence

4
of each observer's rating was equal, regardless of

whether the particular observer tended to rate high or low.

Traffic counts taken in the corridor on various

days indicated approximately 16,000 people tra- versed the corridor per week.

4.2. Test of Materials Laid on Stairway

Specimens of the floor covering, each 10 by 36

in., were installed on a stairway at the National

Bureau of Standards. All specimens were cemented directly to the existing marble treads

with a commercial linoleum paste adhesive. (Two

specimens came loose during the test period.

These were relaid with a rubber-resin adhesive.)

The specimens were mopped twice each week with

water containing 1 percent of (by weight) cleaning

compound. The analysis of the cleaning com- pound used is given in table 4. The test installation was in service from March

1947 to February 1948. At the end of this period,

the test specimens were taken up and washed with

water to which 1 percent of the cleaning compound

was added. They were rated with respect to appearance in comparison with each other as A,

B, C, or D. An "A" rating indicated the best

floor coverings and "B", "C", or "D" progressively poorer materials. Photographs of some of

the specimens, when rated, are shown in figure 4.

5.1.

5. Results of Tests

Correlation of Results of Laboratory

andf Service Tests

The results of laboratory and service tests are given in tables 5, 6, and 7. The results of the

service tests are of primary importance as correlation with these results is used as an index of the

usefulness of any laboratory test in evaluating

durability. The test in the Munitions Building

is thought to be the better criterion of the durability of the specimens, both because use as a floor covering more nearly simulates actual use in the

home than does use as a stair covering, and because

the evaluations of the worn materials represented

the opinions of a larger number of observers with more varied personal background. An analysis of

variance of the service ratings, summarized in

table 7, shows that there are highly significant

differences between specimens, but not between

observers. The results of the service test on the

stairway can be taken as confirming the results of the Munitions Building test. The same two

specimens, C-4 and C-6, are ranked as best, and

the same two, C-7 and C-ll, as "worst." Results

for the other specimens in the stairway test were

inconclusive.

In comparing the results of the floor service test with the results of laboratory tests, correlations were based on rank as the evaluations by the

different observers rated the specimens in order of

Table 6. Results of service tests of printed-enamel felt-base floor covering

Designation

Rating

National Bureau of Standards

installation

Munitions

Building

installation

C-l CB

BA

BAD

C

C

CD

45.0

45.0 47.6

58.0

56.5

67.0

21.6

37.1 54.2

54.3

17.1 42.7

50. 2 56.7

C-2 _._ C-3

C-4

C-5 _ C-6. __ C-7

C-8

C-9... C-10

C-ll C-2A

C-3A B

C-10A __

Table 7. Analysis of variance of adjusted service ratings for

11 printed-enamel felt-base floor coverings by 14 observers

Source of variation Degrees of freedom Sum of squares Mean

square

Between means of floor coverings.. 10

13 130

167. 72 1.37

70. 97

16.77

0.11 .55 Between means of observers

Interaction.. _. .

Total 153 240. 06 1. 57

Table 5. Physical properties and performance tests of floor coverings

Sample Average

weight

Flexibility

Tearing strength Thickness—average

Effect of cleaning compound

Effect of kerosine Machine

direction

Cross- machine

direction

Seal coat Enamel

coat

Over-all

tb/ydi m. a 9 0 Mils Mils Mils in.1 C-l 3.1 3 900 1,060 0.0 5.0 65 5.44 None

C-2 3.0 3H 890 1,270 7.0 5.5 55 0. 06 Do.

C-3.. 2.8 <1 900 1,320 5.0 5.0 51 .02 Do.

C^t 3.3 2 1, 110 1,280 6.0 5.5 66 .01 Do. C-5 3.2 <1 920 1,170 5.0 6.5 61 1.41 Do.

C-6 3.2 2 900- 1,020 3.5 6.0 72 0. 00 Do. C-7 2.0 3H 590 590 4.0 2.0 47 » 57.2 Blistered C-8____ 2.7 4 830 1,130 6.0 5.0 51 0. 67 None

C-9__ 3.6 1 920 940 4.5 4.0 71 .20 Do.

C-10 2.5 3H 570 750 6.0 4. 5 53 .06 Do.

C-ll 2.3 <1 630 700 4.0 0.5 49 " 57.2 Blistered

o Diameter of mandrel on which cracking was first observed. b 6,500 rotations instead of 9,000. ° 4,000 rotations instead of 9,000.
Figure 4. Specimens of floor covering after service test on stairway.

C-7 and C-ll show greatest deterioration, C-6 the least; others are intermediate.

6
Figure 4. Specimens of floor covering after service test on stairway.—(Continued)

C-7 and C-ll show greatest deterioration, C-6 the least; others are intermediate.
Figure 5. Rank correlation of service and laboratory test results.

durability rather than giving quantitative results,

and the final ratings, given in table 6, represent an

integration of these rankings. Diagrams in which

the ranks for each sample in six laboratory tests are plotted against the ranks in the floor service

test are shown in figure 5. From these diagrams it is apparent that there

is practically no correlation between seal-coat

thickness and durability in service, but that there

is some correlation between each of the other properties and the behavior of the material in service.

These conclusions were checked by calculating measures of correlation from ranks, using the

formula

6L>2 p N(N2 -1)'

where

p = the measure of correlation from ranks for a given property

D=the difference between the rank in the

laboratory test for a given property

and the rank in the service test for each

floor covering

N=the number of materials in the test, that

is 11. The values of p so obtained were as follows for

the various properties measured:

Weight per unit area 0. 73 Tearing strength (machine direction) . . 62 Thickness of enamel coat . 69 Thickness of seal coat .08

Over-all thickness . 80

Resistance to cleaning compound .75

Each of these values of p, except that for thickness

of seal coat, shows a significant positive correlation.

5.2. Measurements of Weight and Thickness

As measurements of weight and over-all thick- ness are the easiest and quickest to make of all the tests described in this paper, it is interesting

that they show rather high degrees of correlation

with the results of service tests. As the two

samples giving by far the poorest wear in the

service tests had weights of 2.0 and 2.3 lb/yd2

, it

it would seem that a weight of at least 2.5 lb/yd2 is the minimum that would be expected for a

material giving good service. Similar considerations lead to a minimum value of 0.050 in. for

over-all thickness.

The durability of the enamel coat is highly

important as the decorative effect of the floor covering depends entirely on this layer. When it has become so badly worn as to impair the

decorative effect, the consumer usually wishes to replace it. The significant correlation between the

thickness of enamel coat and the service rating

reflects this circumstance. From the results it would appear that the enamel coat must be at

least 4 mils thick to give satisfactory service.

The purpose of the seal coat is to prevent "bleeding" of the saturant in the felt base into the

enamel coating. It appears that when the minimum thickness necessary to perform this function

is applied, any greater thickness of seal coat adds

nothing to the serviceability of the floor covering.

As one sample had no seal coat, yet showed no

adverse effect from this omission, there is no

conclusive evidence from this experiment that a

seal coat must be required.

5.3. Flexibility

Printed-enamel felt-base floor covering is fur- nished to retail outlets in roll form. Hence it is necessary that the enamel coating be sufficiently

flexible to withstand unrolling of the floor covering

without cracking of the coating. Yard goods,

in addition, are often purchased for use as wall-towall floor covering, and bending of the material will

usually be necessary during fitting at the time of

installation. On the basis of requirements in

existing Federal specifications, 4 felt-base floor covering that can be bent without cracking over

a mandrel 4 in. in diameter or smaller is desirable.

Of the floor coverings included in this investigation only sample C-8 failed to have this degree of

flexibility. After a 3-week period of installation,

the specimen of this floor covering in the service

installation at the Munitions Building exhibited

marked cracking of the enamel coating. All the

other specimens in the service installation at this same time showed either no cracking or slight

cracking of the coating. It was to be expected

that the enamel coatings would harden and lose

flexibility with age. This tendency was evident

in the test at the Munitions Building, for after

approximately 1 year of service, all specimens,

4 Federal Specification LLL-F-471 for Floor Coverings; Felt-Backed.

8
except that from sample C-l, exhibited cracking on some areas of the surface.

5.4. Tearing Strength

The tearing strength is a property of importance in connection with the unrolling and laying

of a floor covering, as well as its resistance to tears caused by stubbing the toe of one's shoe or a

similar hard object against the edge of the covering. This property also shows a significant cor- relation with serviceability. Two of the three

samples having tearing strengths of less than 700 g

were the two showing the poorest durability.

The majority of manufacturers apparently have

no difficulty in making a product with a tearing

strength of 800 g or more.

5.5. Resistance to Gleaning Compound

The statement is sometimes heard in the floor- covering trade that "more floor coverings are worn out by scrubbing than by being walked on."

It seems to be a substantiation of this view that

the results of the test for resistance to scrubbing

with cleaning compound showed a significant

correlation with serviceability. It should be

noted that the two floor coverings that recieved

the lowest service ratings were also the poorest in resistance to cleaning compound, and the two

floor coverings that recieved the highest service

rating were also the best in resistance to cleaning

compound.

Photographs of certain specimens subjected to the test for resistance to cleaning compound are shown in figure 6. The areas of localized exposure

of seal coat or felt on some of the floor coverings can be seen. In certain instances this failure has

occurred at the junction of two colors. This is to be expected on floor coverings when the printing is accomplished by means of die blocks as each color is applied to individual areas without

overlapping. Hence it is necessary for the enamel

to flow slightly to obtain complete coverage of the seal coat. This resultant flow tends to make

the enamel coating thinner at the areas where

colors join. In other instances, failure appears to have occurred at individual colors, probably be- cause these colors were actually less resistant to the action of the cleaning compound. Other

factors that might cause localized exposure of

the seal coat or backing material are poor felting

of the backing material and nonuniformity of thickness of the enamel coating during printing.

The results show that the total area of seal coat

or felt exposed on eight test specimens after 9,000

rotations each should not exceed 50 in. 2 as a max- imum, and it is probable that this value should

be set much lower, perhaps about 8 in. 2

5.6. Resistance to Kerosine

At the beginning of this investigation, the subject of properties to be evaluated was discussed

with manufacturers of printed-enamel felt-base

z

<

o

<

rrO

CD<

_J

02468 10 02468 10 12 SERVICE TEST RANK

Figure 6. Specimens after test for resistance to cleaning

compound.

Upper left, C-l; right, O-ll. Lower left, O-S; right, C-8.

floor covering. It was indicated that a large volume of this floor covering was used in homes in

rural areas and in summer cottages, where kerosine stoves and lamps are frequently used. In

view of the likelihood of spilling of kerosine or seepage from a container placed on the floor covering, it was decided to include an evaluation

of kerosine resistance of the enamel coating.

The results of tests indicated that all the enamel

coatings except two, samples C-7 and C-ll, were

excellent in resistance to kerosine. Samples C-7

and C-ll exhibited blistering of the enamel coat- ing in the test and can not be considered suitable

for an exposure of this type.

5.7. Service Tests

The corridor at the Munitions Building, selected

for the service installation, serves only as a means

for connecting the Munitions Building and the

Navy Department Building. It is used primarily

for pedestrian traffic, but lightweight hand trucks

are occasionally taken through the corridor. Doors

are placed at each end of the corridor only, hence an equal number of people walked over each of the

floor coverings. At the time the specimens were

rated, they had been subjected to 100 cleanings,

and it is estimated that more than 800,000 pedes9
trians had traversed the corridor. Only specimens

C—7 and C-ll had shown a marked loss in decorative effect at the time the ratings were assigned.

The service ratings of replicate specimens of floor coverings C-2, C-3, and C-10 agree very well;

the maximum difference between any two was

found to be 3 units.

An analysis of variance of the ratings of speci- mens C-l through C-ll (the replicates were not

included) was made. This analysis showed that

practically all the variability in the ratings could

be attributed to the floor coverings, and that very

little could be attributed to the observers and

other causes. The specimens installed on the East stairway,

Industrial Building, National Bureau of Standards, were subjected to much more severe conditions

than those in the corridor at the Munitions

Building. The relatively rapid rate of wear of

flooring materials on stair treads is well recognized,

but in this instance the cleaning compound also contained a large percentage of siliceous, material,

which probably further accelerated deterioration.

Although the exposure conditions were widely dif- ferent in the two service tests, the relative order

of results was essentially the same in both tests.

The authors express their appreciation to Helen

G. Wheeler for assistance in the preparation of

specimens and making numerous determinations

of the properties of the floor coverings. The

assistance of John Mandel in the design of experiments and analysis of the data is also gratefully

acknowledged.

Washington, August 24, 1951.

10
BUILDING MATEKIALS AND STRUCTURES REPORTS

[Continued from cover page n]

BMS34 Performance Test of Floor Coverings for Use in Low-Cost Housing: Part 1 150 BMS36 Structural Properties of Wood-Frame Wall, Partition, Floor, and Roof Constructions With "Red Stripe" Lath Sponsored by The Weston Paper and Manufacturing Co 100 BMS38 Structural Properties of Two "Dunstone" Wall Constructions Sponsored by the W. E. Dunn Manufacturing Co 100 BMS39 Structural Properties of a Wall Construction of "Pfeifer Units" Sponsored by the Wisconsin Units Co 100 BMS42 Structural Properties of Wood-Frame Wall and Partition Constructions with "Celotex" Insulating Boards Sponsored by The Celotex Corporation 150 BMS43 Performance Test of Floor Coverings for Use in Low-Cost Housing: Part 2 150 BMS44 Surface Treatment of Steel Prior to Painting 100 BMS47 Structural Properties of Prefabricated Wood-Frame Constructions for Walls, Partitions,

and Floors Sponsored by American Houses, Inc 200 BMS48 Structural Properties of "Precision-Built" Frame Wall and Partition Constructions

Sponsored by the Homasote Co 150 BMS49 Metallic Roofing for Low-Cost House Construction 200 BMS50 Stability of Fiber Building Boards as Determined by Accelerated Aging 100 BMS51 Structural Properties of "Tilecrete Type A" Floor Construction Sponsored by the Tile- crete Co 100 BMS52 Effect of Ceiling Insulation Upon Summer Comfort 150 BMS53 Structural Properties of a Masonry Wall Construction of "Munlock Dry Wall Brick"

Sponsored by the Munlock Engineering Co 100 BMS54 Effect of Soot on the Rating of an Oil-Fired Heating Boiler 100 BMS55 Effects of Wetting and Drying on the Permeability of Masonry Walls 100 BMS58 Strength of Soft-Soldered Joints in Copper Tubing 100 BMS59 Properties of Adhesives for Floor Coverings 150 BMS60 Strength, Absorption, and Resistance to Laboratory Freezing and Thawing of Building

Bricks Produced in the United States 300 BMS61 Structural Properties of Two Nonreinforced Monolithic Concrete Wall Constructions _ 100 BMS62 Structural Properties of a Precast Joist Concrete Floor Construction Sponsored by the Portland Cement Association 150 BMS63 Moisture Condensation in Building Walls 150 BMS64 Solar Heating of Various Surfaces 100 BMS65 Methods of Estimating Loads in Plumbing Systems 150 BMS66 Plumbing Manual 350 BMS67 Structural Properties of "Mu-Steel" Prefabricated Sheet-Steel Constructions for Walls,

Partitions, Floor, and Roofs, Sponsored by Herman A. Mugler 150 BMS68 Performance Test for Floor Coverings for Use in Low-Cost Housing: Part 3 200 BMS69 Stability of Fiber Sheathing Boards as Determined by Accelerated Aging 100 BMS70 Asphalt-Prepared Roll Roofings and Shingles 200 BMS71 Fire Tests of Wood- and Metal-Framed Partitions 200 BMS72 Structural Properties of "Precision-Built, Jr." Prefabricated Wood-Frame Wall Construction Sponsored by the Homasote Co 100 BMS73 Indentation Characteristics of Floor Coverings 100 BMS74 Structural and Heat-Transfer Properties of "U. S. S. Panelbilt" Prefabricated SheetSteel Constructions for Walls, Partitions, and Roofs Sponsored by the Tennessee

Coal, Iron & Railroad Co 200 BMS75 Survey of Roofing Materials in the North Central States 150 BMS76 Effect of Outdoor Exposure on the Water Permeability of Masonry Walls 150 BMS77 Properties and Performance of Fiber Tile Boards 100 BMS78 Structural Heat-Transfer, and Water-Permeability Properties of Five Earth-Wall

Constructions 250 BMS79 Water-Distributing Systems for Buildings 200 BMS80 Performance Test of Floor Coverings for Use in Low-Cost Housing: Part 4 150 BMS81 Field Inspectors' Check List for Building Constructions (cloth cover, 5 x 7% inches) 300 BMS82 Water Permeability of Walls Built of Masonry Units 250 BMS83 Strength of Sleeve Joints in Copper Tubing Made With Various Lead-Base Solders 150 BMS84 Survey of Roofing Materials in the South Central States 150 BMS85 Dimensional Changes of Floor Coverings With Changes in Relative Humidity and

Temperature 100 BMS86 Structural, Heat-Transfer, and Water-Permeability Properties of "Speedbrik" Wall

Construction Sponsored by the General Shale Products Corporation 150 BMS87 A Method for Developing Specifications for Building Construction—Report of Subcommittee on Specifications of the Central Housing Committee on Research,

Design and Construction 200 BMS89 Structural Properties of "Precision-Built, Jr." (Second Construction) Prefabricated

Wood-Frame Wall Construction Sponsored by the Homasote Co 150 BMS90 Structural Properties of "PHC" Prefabricated Wood-Frame Construction for Walls,

Floors, and Roofs Sponsored by the PHC Housing Corporation 150

[List continued on cover page iv]
BUILDING MATERIALS AND STRUCTURES REPORTS

[Continued from cover page ra]

BMS92 Fire-Resistance Classifications of Building Constructions .. 300 BMS93 Accumulation of Moisture in Walls of Frame Construction During Winter Exposure— 100 BMS94 Water Permeability and Weathering Resistance of Stucco-Faced, Gunite-Faced, and

"Knap Concrete-Unit" Walls. 150 BMS95 Tests of Cement-Water Paints and Other Waterproofings for Unit-Masonry Walls 250 BMS96 Properties of a Porous Concrete of Cement and Uniform-Sized Gravel 100 BMS97 Experimental Dry-Wall Construction With Fiber Insulating Board 100 BMS98 Physical Properties of Terrazzo Aggregates 150 BMS99 Structural and Heat-Transfer Properties of "Multiple Box-Girder Plywood Panels"

for Walls, Floors, and Roofs 150 BMS100 Relative Slipperiness of Floor and Deck Surfaces 100 BMS101 Strength and Resistance to Corrosion of Ties for Cavity Walls 100 BMS102 Painting Steel 100 BMS103 Measurements of Heat Losses From Slab Floors 150 BMS104 Structural Properties of Prefabricated Plywood Lightweight Constructions for Walls,

Partitions, Floors, and Roofs Sponsored by the Douglas Fir Plywood Association. _ 300 BMS105 Paint Manual with particular reference to Federal Specifications $1. 25

BMS106 Laboratory Observations of Condensation in Wall Specimens 100 BMS108 Temperature Distribution in a Test Bungalow With Various Heating Devices 100 BMS109 Strtengh of Houses: Application of Engineering Principles to Structural Design $1. 50

BMS110 Paints for Exterior Masonry Walls 150 BMS111 Performance of a Coal-Fired Boiler Converted to Oil 150 BMSI 12 Properties of Some Lightweight-Aggregate Concretes With and Without an Air- entraining Admixture 100 BMS113 Fire Resistance of Structural Clay Tile Partitions 150 BMS114 Temperature in a Test Bungalow With Some Radiant and Jacketed Space Heaters 250 BMS115 A Study of a Baseboard Convector Heating System in a Test Bungalow 150 BMS116 Preparation and Revision of Building Codes 150 BMS117 Fire Resistance of Walls of Lightweight-Aggregate Concrete Masonry Units 200 BMS118 The Stack Venting of Plumbing Fixtures 150 BMS119 Wet Venting of Plumbing Fixtures.. 200 BMS120 Fire Resistance of Walls of Gravel-Aggregate Concrete Masonry Units 150 BMS121 Investigation of Failures of White-Coat Plasters 250 BMS122 Physical Properties of Some Samples of Asbestos-Cement Siding 150 BMS123 Fire Tests of Wood-Framed Walls and Partitions With Asbestos-Cement Facings 150 BMS124 Fire Tests of Steel Columns Protected With Siliceous Aggregate Concrete 150 BMS125 Stone Exposure Test Wall 300 BMS126 The Self-Siphonage of Fixture Traps 200 BMS127 Effect of Aging on the Soundness of Regularly Hydrated Dolomitic Lime Putties 150 BMS128 Atmospheric Exposure Tests of Nailed Sheet Metal Building Materials 200 BMS129 Fire Endurance of Shutters for Moving-Stairway Openings 100 BMS130 Methods and Equipment for Testing Printed-Enamel Felt-Base Floor Covering 150