NATIONAL BUREAU OF STANDARDS REPORT

8950

PROGRESS REPORT

April 1 through June 30, 1965

PORCELAIN ENAMEL INSTITUTE RESEARCH ASSOCIATESHIP

NATIONAL BUREAU OF STANDARDS

WASHINGTON, D. C.

<nb|>

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NATIONAL BUREAU OF STANDARDS
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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

42108=1 1 "4210180 8950

PROGRESS REPORT

April 1 through Juiie 30 ^ 1965

PORCELAIN ENAMEL INSTITUTE RESEARCH ASSOCXATESHXP

NATIONAL BUREAU OF STANDARDS

WASHINGTON, D. Co

IMPORTANT NOTICE NATIONAL BUREAU OF ST,

for use within the Government, and review. For this reason, the whole or in part, is not author Bureau of Standards, Washingtc

the Report has been specifically

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST)

on October 9, 2015.

s accounting documents intended

subjected to additional evaluation

listing of this Report, either in Office of the Director, National

the Government agency for which

ipies for its own use.

U. S. DEPARTMENT OF COMMERCE

NATIONAL DUREAU OF STANDARDS

PROGRESS REPORT

April 1, 1965 through June 30, 1965

PORCELAIN ENAMEL INSTITUTE RESEARCH ASSOCIATESH1P

NATIONAL BUREAU OF STANDARDS

/ WASHINGTON, D. C.

SUMMARY

Two measurement approaches were used to detect the amount of

fluorescent soil remaining on a specimen after a "standard" cleaning

treatment. In the first, the test area of the specimen was soiled

with anthracene, cleaned and then irradiated with an ultraviolet

light source. The amount of residual soil was then determined by the

intensity of the emitted fluorescent (visible) radiation. The instrument used for these measurements was a modified. Hunter Multipurpose

Reflectometer. Poor results were obtained mostly because of the unavailability of suitable filters at a reasonable cost.

The second approach involved dissolving the residual soil from

a fixed area of the specimen in a known amount of benzene. The fluorescence of the resulting solution was then evaluated. A Turner

fluorometer was used to measure the fluorescence. Initial results

with this approach were promising. Benzene was found to have a combination of properties which would recommend its use as a solvent for

removing anthracene from porcelain enamelled surfaces.

Work directed toward a test method to evaluate the continuity of

porcelain enamel coatings was continued. Some indications have been
- 2 -

obtained that a simple electrical discharge test may serve to Indicate

the acceptability of porcelain enamel coatings for various types of

service,

I. CLEANABILITY

INTRODUCTION

Previous progress reports in this series have outlined the needs

for a test method to evaluate the cleanability of porcelain enamels

and perhaps other competitive finishes. Two possible approaches have

been considered: (l) finding a suitable method for evaluating either

the ease of removal or the soil remaining after a standardized cleaning treatment when using individual soiling agents or a composite soil,

and (2) using a fluorescent solid to simulate the common soils and

then evaluating the fluorescent solid remaining after a standardized

cleaning treatment by measuring the intensity of the emitted radiation

on exposure to an ultraviolet source.

Use of the first approach is complicated by the need for several

soiling agents that will be both strongly adherent and easy to standardize, It is also difficult to determine when soil removal is complete

by reflectance measurements especially when non-white specimens are

evaluated. However, since a fluorescence approach should work equally

well with white or colored specimens and since it is potentially

capable of evaluating small differences in "cleanability”, major

attention during this report period has been directed to the fluorescent method.

SURVEY CF METAL-CLEANING TESTS

A literature survey was made of test methods used in metal-cleaning.
- 3 -

The principal problem in establishing a cleanability method for porcelain enamels is in finding a way to quantitatively determine the

amount of small residues on a surface. This is precisely the problem

encountered in evaluating metal cleaners and cleaning techniques.

Morgan and Lankier in 19^2 devised a method for photographically recording the intensity of the fluorescence of mineral oil remaining on meted surfaces which had been cleaned. The claim that this

method could detect as little as 4 micrograms of oil per square centimeter was supported by gravimetric determinations of the oil extracted

from similar soiled surfaces. The method was accurately described as

"visually quantitative" because of the necessity of a visual comparison

of the photographs.

Edeler —/ suggested that small residues of oil of the order of

one part in 20,000 of solvent could be determined by dropping the

volatile solvent from the cleaned panel onto photographic quality

ground glass and observing for a ring appearance due to any nonvolatile oil present.

Harris, et al

^

mentioned the time-honored "water break" test

for soil retention which is quite sensitive to oily or greasy films.

They also state: "Another recognized method for estimation of the

degree of cleanliness is either to weigh the metal piece being cleaned

before and after the cleaning process, or to wash the cleaned piece

with solvent and weigh the extract. This method suffers when the amount

of soil remaining is less than the sensitivity of the balance in use."

This earlier work on metal-cleaning tests suggested a possible

test procedure for porcelain enamels. This would involve measurement
- k -

of the residual fluorescent soil on a surface by first extracting the

soil with a suitable solvent and then evaluating the amount of residual

soil that was present by measuring the fluorescent intensity of the

resulting solution with a commercially available fluorometer.

RESULTS AND DISCUSSION

1. Tests with the Modified Hunter Multipurpose Reflectometer.

In a search for a suitable instrument with which to measure the

intensity of fluorescence remaining on specimens that had been soiled

and then cleaned, trials were made with a modified Hunter Multipurpose

Reflectometer. Early trials with this instrument, made in the preceding report period, indicated that difficulties could be expected in

separating that part of the signal due to specimen color or reflectance

from the part due to the fluorescence of the residual soiling agent.

The multipurpose instrument was specifically designed as a reflectometer for operation in the visible. In order to measure fluorescence

it was necessary not only to replace the tungsten lamp with an ultraviolet source but also to introduce suitable filters so that the photocells would respond only to the fluorescent light emitted by the residual

fluorescent soil on the specimen and not to radiation from the source

that was reflected by the specimen onto the photocell.

This last requirement will be difficult to resolve completely

since commercial filters with the necessary narrow band-pass are not

available at a reasonable cost. Hence, it is necessary to use filters

that are not 100^ efficient. To determine whether filters of this

type could be made to work in the modified instrument a number of tests

were made
- 5

-

In the first tests of this kind the instrument was first

balanced to a null position on a specimen with no fluorescence, with

the reflectance photocell near its front position (12 cm). Next, a

small square of a fluorescent uranium glass, 0.22-in. by 0.22- in. by

0.039-in. was attached to the center of the specimen and a reading

taken. The distance through which the travelling photocell needed to

be moved to reestablish the null balance of the photocells was determined. If the filters were effective this distance should represent

the apparent intensity of the visible radiation emitted by the fluorescent glass. When the same piece of glass was attached, in turn,

to a series of specimens of various colors, it can be seen from

Table I, however, that the photocell responses depended quite strongly

on specimen color.

One might wonder why the instrument response should be 19*5 cm

(31.5 - 12.0) when the fluorescent glass was attached to a black specimen, but only 2.6 cm when attached to a white specimen. Basically, it

is due to poor filtering. The explanation follows: The net change in

the response of the photocell which resulted from the attachment of

the fluorescent glass consisted of two components which acted simultaneously: (l) radiation emitted by the fluorescent glass, a positive

component, and (2) a reduction in the amount of reflected flux which

resulted from shielding a part of the irradiated specimen face with

the glass plate. The reduction (component 2) in the case of the

black specimen was quite small compared to that of the white specimen

because of the low reflectance of the dark colored specimen. Thus,

the net result of the two components for the black specimen was larger
- 6 -

than for the white one.

The value of the aforementioned experiment is in demonstrating

the great need for suitable filters in the instrument. In fact, without such filters the modified instrument has little value for the intended application.

(a) Tests of New Filters . The following three filters were tested:

Filter Transmission Type

at 365 mp.

percent

7-60 55

7-37 21

365-Int 29

Corning colored glass

Corning colored glass

Interference, 2nd order

Measurements were made with these filters in the instrument. This

was done by measuring the fluorescent intensity of a piece of uranium

glass superimposed, in turn, on a black and a white specimen as previously described. The results are given in Table 2. In two of the three

filter combinations, the indicated fluorescent intensity was greater

from a black specimen than from a white one. This is in qualitative

agreement with the results given in Table 1 . In this comparison a

0.1 neutral density filter was used in conjunction with the 7-60 filter

so as to partially equalize differences in their transmission properties. The smaller responses for both the black and the white specimens,

given in Table 2, undoubtedly resulted from the resulting reduction of

transmitted energy.

A comparison of the filters was also made by depositing known

amounts of a saturated alcohol solution of anthracene on black and

white specimens and, after drying, obtaining an instrumental indication
7

of the fluorescent intensity,, The weights of anthracene applied were

based on its solubility in alcohol at 20°C (0.76 g in 100 ml) and the

volume of a drop from a 1-ml Mohr pipette (0.19 ml). The results in

Table 3 show that the galvanometer deflections were roughly proportional

to the amount of anthracene, but the differences in deflection between

black and white specimens were quite unsatisfactory with any filter combination that was tried.

(b) Conclusion . The results given in Tables 1 to 3 indicate that

the modified multipurpose ref le ctometer is unsuited for measuring the

intensity of the fluorescence of anthracene, "in situ", on a wide range

of porcelain enamel colors. The disqualification of this instrument for

fluorescence measurements rests squarely on the unavailability of narrow

band-pass filters. As stated earlier, such filters are necessary to

separate the influence of a specimen's reflectance from the property to be

measured

.

2. Tests With a Turner Fluorometer.

The experiments with the modified Hunter instrument were directed

toward the measurement, in situ, of fluorescent soiling agents remaining

on cleaned specimens. The second approach investigated was to extract

the residual soil with a solvent and then to evaluate the amount of soil

that remained on the specimen by measuring the fluorescence of the resulting

solution. This type of measurement can be made with high precision with

commercially available instruments. Because of the promise indicated by the

extraction approach, a Turner Fluorometer was purchased by NBS and made

available to the Research Associateship. The instrument operates on the
8

double-beam principle. In effect, it measures the difference between

fluorescent light emitted by the sample and the direct light from a reference beam. The same light source is used to irradiate the sample

and to supply the reference light beam. Light source variations cannot

affect the light balance since sample and reference beams are equally

affected. Measurements are made on about 5 ml of solution and through

the use of a calibration curve can be expressed in units of weight of

fluorescent material per unit area of specimen surface. Accurate fluorescence measurements depend, of course, on careful extraction and dilution

techniques as well as on the use of reagents of known purity, uniformity

and stability.

A requisite of the extraction method was the selection of a suitable

solvent for the extraction and dilution of anthracene. The degree of solubility of anthracene, the volatility of the solvent, and the intensity of

its fluorescence were considered of importance. Table 4 gives these

properties for five common organic solvents which might be considered. The

study of these properties resulted in the selection of benzene which has

the lowest volatility, a good solubility for anthracene and an acceptably

low fluorescence.

The new instrument was received late in the report period which precluded any extensive trials of the extraction approach to cleanability.

However it was possible to check the sensitivity capabilities of the

instrument. These showed considerable promise. Anthracene concentrations

in benzene of as low as 0.001 micrograms per milliliter (one part per billion)

could be easily measured with the instrument.
9

3. Experiments with Domestic Soils.

Before the fluorescent soil approach could receive any wide degree

of acceptance when incorporated into a cleanability test, it would first

be necessary to show that the test results correlated with the ease with

which some of the more common soils could be removed from various types

of finishes. As a first step toward this goal, a preliminary study was

made of soiling agents that might typify soils encountered in the home.

In studying the cleanability of porcelain enamels, one difficulty

that has been encountered is that many soiling agents clean off too easily

and do not allow one to discriminate between one porcelain enamel and

another. The other extreme, of course, occurs when a soil (such as nail

polish) is retained so tenaciously that special solvents or extreme abrasion

must be resorted to.

(a) Tests with Kitchen Soils . The relative effort required to remove

several domestic kitchen soils from a single enamel was investigated. The

results are given in Table 5, which also includes a description of the soils

and the hand-rubbing methods that were used. It is interesting to note that

the two operators placed the soiling agents in the same order with respect

to the effort required to remove them from the enamel surface.

An egg-mixture was used on several different enamels and on glass to

determine if a more objective, mechanical cleaning method could measure the

effort or time required for cleaning, and thus discriminate between the
10

types of finishes studied. Mechanical dry-rubbing as outlined in Table 6

was used to show differences in cleaning time required for different

surface finishes. Enamel Q and the glass specimens retained the baked

egg-mixture so tenaciously that the dry-rubbing used failed to completely

remove the deposit in a reasonable time. Two of the enamels, Y and A,

required only two to six minutes for complete removal as judged by visual

observation. The same soil on other specimens of the same enamels were

cleaned by wet-rubbing in times too short to measure.

(b) Powdered Graphite as a Soiling Agent . When powdered graphite

was used as a soiling agent on white enamels, reflectance measurements

were used to determine how much soil remained after uniform amounts of a

cleaning treatment. The results, given in Table 7, indicate that graphite

is a soiling material which is quite difficult to remove and that there

were marked differences between dry and wet mechanical rubbing. The

variable character of the reflectance measurements, however, did not

indicate any statistically significant difference between enamels A and Y

after either dry or wet rubbing.

FUTURE PLANS

Work during the next report period will be concerned with: a) Further

experiments with the Turner fluorometer to determine its applicability for

the determination of the cleanability of porcelain enamels, b) The development of soiling and cleaning techniques with fluorescent soiling agents,

c) Development of a cleanability test that will permit qualitative ratings
1

1

of the ease of cleaning of specimens so that these ratings can be compared

with measurements made by the fluorescent approach.

II. CONTINUITY OF COATING

INTRODUCTION

Protection of the base metal from corrosion is one of the prime reasons

for using a porcelain enamel coating on a metal product. In a previous

report, methods that have been used for measuring continuity of coating

were discussed. Of these methods, the one that appeared most promising

for a standard continuity of coating test was the high-voltage discharge

test.

RESULTS AND DISCUSSION

Before progressing too far into the factors affecting the high-voltage

discharge method, it seemed desirable that the research associates should

visit several plants to ascertain how industry copes with the problem of

discontinuities in porcelain enamel coatings. Trips were made to plants

engaged in the manufacture of (a) frit, (b) hot water tanks, and (c) highvoltage test equipment.

Many aspects of continuity of coating were discussed during our visit

to the frit company. A discussion of (a) the types of discontinuities and

(b) the methods of test that have been used to determine discontinuities

revealed one test in addition to those given in the previous report. This

is the rust spot test. It consists of first forming a reservoir on the

enameled surface with any good calking compound, and then filling the reservoir

with an aqueous solution consisting of 1% by weight sodium chloride and 1/2%

sodium carbonate. Next, a DC potential of 9 volts is applied for 15 minutes

between the solution and the metal backing of the specimen. At the end of
12

this time, the enameled surface is washed and the number of rust spots is

counted. According to current practice, the acceptable number of rust spots

permitted for an appliance enamel is five per twelve square inches. It was

also stated that the products that are most susceptable to rust spots caused

by non-continuous coatings are dishwashers, laundry baskets, and architectural

panels. An interesting sidelight of this visit was observing the methods used

in their laboratory for preparing polished cross-sections of porcelain enameled

specimens and taking photomicrographs.

This particular frit manufacturer has agreed to prepare several specimens of one enamel both with and without defects. These specimens will permit

us to compare acceptable and unacceptable enamels by a number of different

test methods.

The visit to the hot water tank plant was also interesting. The need

for a continuous coating is not so great for enameled hot water tanks since

the magnesium anode inserted before shipment prevents rusting at any small

discontinuities that may be present. It was the feeling of this manufacturer

that a continuity of coating test would be used mostly as an acceptance test,

since the checking of each tank for a continuous coating as it came off

the production line would be a slow and costly operation. This company has

prepared several water tank enamel specimens, both with and without defects,

for use in our development of a continuity of coating test.

A visit to the manufacturer of high-voltage test equipment for glasslined steel tanks for the chemical industry provided us with many interesting

facts on their high-voltage test equipment. Although the tanks that they test

are made with much thicker coatings than are applied to ordinary porcelain
13

enameled products, they find that an AC voltage of 5 KV will locate areas

that may give corrosion difficulties. The tanks are tested before they

are installed and also after periodic periods of service. If punctures

occur on any area at a voltage of 5 KV, repair of this area is indicated.

These three visits were interesting and informative but they left a

few questions unanswered in the Research Associate's minds. In an effort

to get a more thorough understanding of the opinions of the industry on

the subject of continuity of coating, a questionnaire to the fabricator

membership of PEI has been prepared.

Meanwhile, the types of defects located with the high-voltage tester

have been studied in further detail. Specimens of architectural enamels

that duplicate those which had rusted in service were tested with the highvoltage test equipment. The specimens were tested at increments of 0.2 KV

from 0-5 KV. The defects located were marked, sectioned, and examined with

a metal lographic microscope. Photomicrographs of defects detected in one

architectural enamel are shown in figure 1

.

The microscopical examination revealed the types of defects that are

detected with the high-voltage tester. Cracks, blisters, pinholes, subsurface pores, and contamination in the surface of the enamel were located at

relatively low voltages. Copperheads in ground coat enamels were also

located, but generally higher voltages were required. The majority of the

detected defects consisted of pinholes, blisters, and subsurface pores.

An examination of any one enamel indicated that the voltage required to

puncture the coating at a subsurface bubble was a function of the thickness
14 -

of the enamel over the bubble (see figure 2). However, slight differences

in the enamel composition appear to affect the dielectric strength so this

relationship becomes masked when all the enamels are considered. Therefore,

if this method of test is to be used as a non-destructive test, preliminary

testing of each enamel, sectioning and measuring the thickness of enamel

over the defects might be necessary to determine the proper test voltage.

In the architectural enamels studies, no corrosion seemed to occur in seven

years at a severe seacoast site if the thickness of enamel over the bubble

was greater than about 0.0005 in.

A somewhat more desirable goal in coating continuity might be to arrive

at a test voltage that would separate enamels with acceptable and unacceptable

coverage. Fairly clear-cut dividing lines seem to be forming for the enamels

tested to date. Many of the enamels tested were duplicate specimens of

architectural enamels which had been subjected to long-time weathering tests.

The specimens were probed to located discontinuities as previously described.

In this way the number and type of defects could be associated with the results on similar specimens from long-time exposure testing. Four of the

five enamels that had failed at six years* service had defects on the storage

specimens which were detected at 0.8 KV; 12 of the 15 enamels tested that

failed after seven years* exposure had defects which were located under 2.5 KV;

while three enamels tested which had not failed in seven years* exposure, had

no defects detectable at less than 3 KV.
15

The hot-water-tank enamels need not be as free of coating discontinuities

as other enamels since the magnesium anode offers protection for small

localized failures. For this reason, these enamels might be tested at a preselected voltage, say 5 KV, and the good enamels separated from the bad

by the difference in the number of defects detected. In the testing of "good"

and "bad" hot-water-tank enamels it was observed that the "bad” enamel showed

approximately five times as many punctures when tested at 5 KV as did the

"good" enamel. Figure 3 illustrates the number of defects located in these

two hot-water- tank enamels at the different voltages.

PLANS FOR NEXT REPORT PERIOD

It appears that the high-voltage test equipment could be adapted for an

acceptance testing of porcelain enameled products. However, many more enamels

need to be tested before voltage limits can be established. Requests for

specimens with and without defects have been made to a number of fabricators.

Additional tests will be conducted as soon as these specimens are received.

III. EXPOSURE TEST OF PORCELAIN ENAMEL ON ALUMINUM

INTRODUCTION

During the preceding quarter, the exposure test of porcelain enamels

on aluminum, authorized by the Aluminum Council of the PEI, became a reality

with the installation of triplicate specimens of 51 enamels at Kure Beach,

North Carolina (80 feet from the ocean), Washington, D. C., and Montreal,

Canada.
16

RESULTS AND DISCUSSION

During this quarter, exposure specimens were installed at New York

City and Los Angeles. In addition, spall tests on triplicate specimens

of each enamel were completed. Some spalling occurred on seven enamels

(AA-C, AB-A, AB-C, AD-B, AD-C, AE-A, and AW-B) after 96 hours* exposure

in ammonium chloride. However, since this spalling did not occur on all

three of the specimens and since the spalled areas were all less than 1/8

inch in diameter, these seven enamels all passed the ASTM test for spall

resistance.

PLANS FOR NEXT REPORT PERIOD

The specimens exposed at Washington, Montreal, and Kure Beach will

be returned to the National Bureau of Standards and inspected after

exposure for six months.
17

STANDARD REFERENCE MATERIALS

The following stock of standards was on hand July 1 , 1965:

Corundum abrasive, March 1960 issue,

for subsurface abrasion • •••••«••••• 293 lb., 73 jars

Standard Pennsylvania Glass Sand, July 1963 issue,

for surface abrasion . „ . 0 285 lb., 97 jars

Distinctness of image gloss standards . ...... . ... 20 sets

Calibrated glass plates for abrasion testing . 27.5 doz.

Respectfully submitted,

M. D. Burdick

M. A. Rushmer

Research Associates, PEI
18

REFERENCES

1, 0, M. Morgan and J. G. Lankier, Evaluation of Metal-Cleaning

Compounds, Indo and Engr. Chem.

,

Anal. Ed.

2 e A. Edeler, Indo and Engr. Chem.

,

Anal. Ed.

3c J e C 0 Harris, R. E. Kamp, and W. H. Yanko,

Removal in Metal- Cleaning by the Radioactive Tracer Technique,

J. Electrochem. Soc„, 97

,

430-32 (1950).
TABLE 1. The Effect of Superimposing a Small Uranium

Glass Plate with Constant Fluorescence Intensity on a Series

of Porcelaing Enamels Ranging From Black to White.

Final balance with

Specimen

Color

Initial Null Balance

on Bare Specimen-7 uranium glass superimposed at specimen

center^'

b / b/

cm.— cm.—

Black 12.0 31.5

Black 12.0 29.8

Dk. Blue 12.0 21.1

Lt . Blue 12.0 15.8

Lt . Blue 12.0 15.0

Med. Blue 12.0 15.1

Lavender 12.0 15.7

Buff 12.0 15.7

White 12.0 15.1

White 12.0 14.6 —^ Measurements with a Hunter Multipurpose Ref lectometer , modified with a mercury- arc source, a CS 7-60 primary filter, and a Wrattan No. 3 secondary

filter

.

b/ Distance of movable photocell from specimen.
lo 10913 3 9/fT . f SJ3AT

•j*foui3 3n&3ancD d3iw arfsH aeaiD

: “ 1 9atBa _ > xpf io

ffiij i iTs i U 1 i sjiiB s gnl soqnil *r

a

S9i^s3 jb no yllanolnl sorio:

. aijtriW :Iob1 & mori gr

TABLE 2. Measurements of the Intensity of Fluorescence of a Standard Uranium Glass Superimposed of Black and White

Porcelain Enamels using Different Primary Filters.

fteiv sonalsd IbhII

-I9qU8 M.I8

. I9mioa S Black Specim

^nrsiiiQo Initial Balance With Initial Balance With

Filter , Balance U-Glass Ad Balance U- Glass “ mo

cm. cm • OIO cm. cm. cm • e.xe • 7-60+0 . 1 ND es 10.0 13.2

O.SI

3.2c 10.0 11.8

7-37 10.0 11.0 1.0 c 10.0 12.4

365- Int. 8. ci 10.0 13.0 3.0 10.0 10.5

0.

ei

1. a

S . Ci

s.ei

i . ?j.

d . Ai

0. SI

o,u

0 .££

G. SI

o.si

0. si

cm.

1.8

J2.4

“0:5

ff . U

9/jIS . IJ

suia . bsM

isbnovBj

IluS

srJirfW

siidW

S rfi 'T

!,al'

nb0m <»ls«0i39li9a 980q3Xiqi Jll/M 19301® E rfiiw *309«930«B9M T b«0=9S t .oH n*33siw £ Wis ,193113 xismlTtq Od-V 20 s , 93300s oiB-vTuoism

. isilii

. (ISOI me 1. : soododq sldsvom 3o sonBdaiU \d
TABLE 3. Measurement of the Intensity of Fluorescence of

Anthracene Deposited on Black and White Specimens of Porcelain

Enamels Using Various Primary Filters in the

Multipurpose Ref lectometer

.

Filter Volume of

Reagent

Weight of

Anthracene

Galvanometer

Black

Specimen

Deflection

White

Specimen

drops pg div div

7-37 0 0.0 0.0 2.9

1 14.4 10.5 >50.

2 28.8 18.0 If 3 43.2 21.0 II 4 57.6 33.0 II

365-Int 0 0.0 2.0 >50.

1 14.4 15.0 >50.

2 28.8 27.2 II 3 43.2 42.2 It 4 57.6 48.8 II

7-604*0 . 1 ND 0 0.0 0.4 8.0

1 14.4 14.5 >50.

2 28.8 24.2 • 1 3 43.2 41.0 II 4 57.6 44.2 It
TABLE 4. Properties of Some Organic Solvents

for Anthracene

.

Solvent

Relative

Fluorescence .of

Solvent—

Anthracene^olubility

r in 100 ml

Boiling

Point

°C

Carbon disulphide 1.0 1.5 46

Chloroform 1.5 1.7 61

Benzene 3.0 1.3 80

Ether 23.0 1.2 35

Ethyl Alcohol 80.0 0.08 78

Q / — These measurements made with the Turner Fluorometer give the f luorescene

of the solvents without the addition of any other material. They were

"blank" determinations. — Data from "The Dictionary of Organic Compounds," I. Heilbron, Oxford

UniV. Press, New York 1934-38.
TABLE 5. Relative Effort Required to Remove Domestic Soils

from Specimens Prepared from the Same Enamel

3- / Soiling Agent —

1

2

3

4

Number of Strokes Required to Clean

.

Operator A Operator B

Dry Wet Dry Wet

Rubbing Rubbing Rubbing Rubbing

250 — 268 -- 100^ 3 100^ 28

100^/ 70 100^ 112

100^ 115 200^/ 132

9. / — (1) Soap flakes, water, and red food color.

(2) Instant coffee, evaporated milk, and sugar.

(3) Evaporated milk and food color.

(4) Black Magic Marker.

Note: All soils except No. 4 were thoroughly blended on magnetic stir plat

Equal, small amounts of the four soils were applied to a single

specimen of Enamel Y for each operator, oven dried, and cooled to

room temperature before cleaning. The cleaning treatment was by

rubbing with a dry or moist cloth using a light pressure.

b/

No progress toward cleaning.
TABLE 6 . Time Required for Soil Removal

From Various Materials

Specimen Material Enamel Y Enamel A Enamel Q Glass Glass

Condition New New New Polished Abraded

Specimen No. Min

.

Min

.

Min. Min. Min.

1 2.6 b/ 36"t - 39

"^ il/ 36-U7

2 6.5 b/ 36t

^

b/ b /

3 2.2 2.0 36t - b/ b/

4 1.7 6.2 36t - b/ b/

— Not completely cleaned, a small amount of soil was tenaciously retained,

b/— Not determined.

Notes on Soil preparation, application and cleaning treatment . The soiling agent consisted of:

Egg mixture (1 yolk, 1 white) 50 ml.

Water 50 ml.

Red food color to make a pink soil

The mixture was homogenized for 5 minutes on a magnetic stir plate,

strained thru 200 mesh. Five drops of the soil was applied at the center

of a 4 x 4 inch specimen, dried on a hot plate and oven dried at 60 C.,

overnight. Cleaning was by dry rubbing with the mechanical lap. The

specimen rotated face up at 78 RPM. A felt-covered brass disc-shaped

head was caused to bear on the specimen and pass back and forth along a lap diameter at 22 passes per minute. The three- inch brass disc used in

this experiment weighed 840 grams.
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DIELECTRIC

PUNCTURES

TEST VOLTAGE - KV

Figure 3. Total number of dielectric failures obtained

on four-inch square specimens of "acceptable"

and "unacceptable" hot water tank enamels.