I. ^

JtM 11967 NBS MISC. PUBL. 260*15

A111D3 DflSbbT

soStandard Reference Materials:

RECOMMENDED METHOD OF USE OF STANDARD

LIGHT-SENSITIVE PAPER FOR CALIBRATING CARBON ARCS

USED IN TESTING TEXTILES FOR COLORFASTNESS TO LIGHT
THE NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards1 provides measurement and technical information services

essential to the efficiency and effectiveness of the work of the Nation's scientists and engineers. The

Bureau serves also as a focal point in the Federal Government for assuring maximum application of

the physical and engineering sciences to the advancement of technology in industry and commerce. To

accomplish this mission, the Bureau is organized into three institutes covering broad program areas of research and services: THE INSTITUTE FOR BASIC STANDARDS . . . provides the central basis within the United

States for a complete and consistent system of physical measurements, coordinates that system with the measurement systems of other nations, and furnishes essential services leading to accurate and uniform

physical measurements throughout the Nation's scientific community, industry, and commerce. This

Institute comprises a series of divisions, each serving a classical subject matter area: —Applied Mathematics—Electricity—Metrology—Mechanics—Heat—Atomic Physics—Physical Chemistry—Radiation Physics—Laboratory Astrophysics2—Radio Standards Laboratory, 2 which

includes Radio Standards Physics and Radio Standards Engineering—Office of Standard Refer- ence Data. THE INSTITUTE FOR MATERIALS RESEARCH . . . conducts materials research and provides

associated materials services including mainly reference materials and data on the properties of materials. Beyond its direct interest to the Nation's scientists and engineers, this Institute yields services which are essential to the advancement of technology in industry and commerce. This Institute is or- ganized primarily by technical fields: —Analytical Chemistry—Metallurgy—Reactor Radiations—Polymers—Inorganic Materials—Cryogenics 2—Office of Standard Reference Materials. THE INSTITUTE FOR APPLIED TECHNOLOGY . . . provides technical services to promote the use of available technology and to facilitate technological innovation in industry and government. The

principal elements of this Institute are: —Building Research—Electronic Instrumentation—Technical Analysis—Center for Computer Sci- ences and Technology—Textile and Apparel Technology Center—Office of Weights and Measures —Office of Engineering Standards Services—Office of Invention and Innovation—Office of Vehicle Systems Research—Clearinghouse for Federal Scientific and Technical Information3—Materials Evaluation Laboratory—NBS/GSA Testing Laboratory.

1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D. C,

20234.

2 Located at Boulder, Colorado, 80302.

3 Located at 5285 Port Royal Road, Springfield, Virginia 22151.
UNITED STATES DEPARTMENT OF COMMERCE • Alexander B. Trowbridge, Secreta NATIONAL BUREAU OF STANDARDS • A. V. Astin, Director

Standard Reference Materials:

Recommended Method of Use of Standard

Light-Sensitive Paper for Calibrating Carbon Arcs

Used in Testing Textiles for Colorfastness to Light

Elio Passaglia and Paul J. Shouse

Institute for Materials Research

National Bureau of Standards Washington, D.C.

National Bureau of Standards Miscellaneous Publication 260-15

Issued July 21, 1967

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price 20 cents

PREFACE

Within the framework of the MBS Institute for Materials

Research the area of standard reference materials is a broad

and important one, including the preparation, characterization

and distribution of a wide variety of materials in such diverse

fields as metallurgy, polymers and inorganic materials. In carrying out such a program there is much interaction with

representatives of industry and science, beginning with discussions as to which primary standard materials will do most

to advance technology, the furnishing of materials and fabrication of samples, and the characterization and certification

of the materials by cooperative efforts. The many groups participating in a standards program are very interested in detailed information on specific aspects of the program — but

to date there has been no publication outlet for such written

discussions 0 To meet this need, MBS Miscellaneous Publication 260 has

been reserved for a series of papers in the general area of

"standard reference materials". This series will present the

results of studies and investigations undertaken within the

Institute for Materials Research with emphasis on the preparation and characterization of standard reference materials.

This subject-oriented series will provide a means for rapid

dissemination of this detailed information and we hope will

stimulate the use of standard reference materials in science

and industry.

W 0 Wayne Meinke, Chief

Office of Standard Reference Materials

iii
OTHER NBS PUBLICATIONS IN THIS SERIES

NBS Misc. Publ. 260, Standard Reference Materials: Catalog

and Price List of Standard Materials Issued bv_ the National

Bureau of Standards, October 1965. 45 cents. (Supersedes

NBS Misc. Publ. 24l s March I962.)

NBS Misc. Publ. 260-1, Standard Reference Materials: Preparation of NBS White Cast Iron Spectrochemical Standards } June

1964. 30 cents,*

NBS Misc. Publo 260-2, Standard Reference Materials: Preparation of NBS Copper-Base Spectrochemical Standards s October

1964. 35 cents.*

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Steel Standard, October 1964. 20 cents.*

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of Information on Standard Reference Materials, February

1965. 20 cents.*

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of Solution X-Ray Spectrometric Analysis of Copper-Base

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for the Chemical Analysis of White Cast Iron Standards, July

1965. 45 cents.*

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Standards 5 October 1965o 60 cents 0 *

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of Uranium Concentrates at the National Bureau of Standards

December 1965. 55 cents

»

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of a Standard Lead-Silica Glass. November 1966. 25 cents.

iv
KBS Misco Publ. 260-12 3 Standard Reference Materials: Homogeneity Characterization of KBS Spectrometric Standards III: White Cast Iron and Stainless Steel Powder Compact. September 1966. 20 cents,*

KBS Misco Publ, 260-13, Standard Reference Materials: Mossbauer Spectroscopy Standard for Chemical Shift of Iron Compounds. (In press.)

KBS Misc. Publo 2.60-lA s Standard Reference Materials: Determination of Oxygen in Ferrous Materials SRM 1090, 1091, and

1092. September 19660 30 cents 0 *

Send orders with remittance to: Superintendent of Documents } Uo S. Government Printing Office s Washington, D 0 Co 20402.

Remittance from foreign countries should include an additional

one-fourth of the purchase price for postage,,

v
TABLE OF CONTENTS

PAGE

1. INTRODUCTION „ „ . . . . . . . . . 2 Light Sensitive Paper . 0 . . . • » . . . . . . . 2 NBS Standard Lamp . 0 • . • 0 o o . . » . • . . . 3 2o EXPOSURE OF PAPERS . . , 4

Limitations of Papers •...•.•••o.. 4

Procedure for Exposure „ • • . . 0 . o 5 3. RATING OF THE PAPERS AFTER EXPOSURE ........ 7 Visual Estimation . . . & , . . . 7 Measurement of Fading by Reflectance • . . 0 . . . 9 4. PROCEDURE FOR ORDERING PAPER AND BOOKLETS . . . . 12

5. REFERENCE „ . . . . , . . „ . . „ „ 13

Table of Luminous Reflectance Factor Y as Measured

on a Gardner-Type Color-Difference Meter Model C-l

vs SFH for Light-Sensitive Paper 14

Figure: Luminous reflectance factor Y (green filter) versus standard fading hours exposure for

Standard Sample No c 700b Light-Sensitive Paper . . . 15

vi
RECOMMENDED METHOD OP USE OF STANDARD

LIGHT-SENSITIVE PAPER FOR CALIBRATING- CARBON ARCS

USED IN TESTING TEXTILES FOR COLORFASTNESS TO LIGHT

Elio Passaglia and Paul J. Shouse

Institute for Materials Research

National Bureau of Standards

Washington, D.C. 20234

ABSTRACT

The use of NBS Light-Sensitive Paper and NBS Booklets of Standard Faded Strips in the standardization of

fading lamps is describedo These lamps are used to determine the fading characteristics of textiles s and the

light-sensitive paper is thus useful in standardizing

this procedure©

Key words: Light-Sensitive Paper; Booklets of

Faded Strips; Fading Characteristics; Textiles; Fading

Standardization.

1
1. INTRODUCTION

Light Sensitive Paper

Standard light-sensitive paper (NBS Standard Reference

Material 700b) and booklets of standard faded strips of this

paper (NBS Standard Reference Material 701b) are sold by the

National Bureau of Standards for use in standardizing the

dosage of the radiant energy of commercial carbon-arc lamps

especially those used for testing textiles for colorfastness

to light. These lamps vary in radiant output from one to another and from time to time. The lack of duplicability

in their performance must be taken into consideration in

using them 0 The paper may be used to check the performance

of lamps in order to predict the number of clock hours of

exposure that will be required to produce fading corre- sponding to a specified number of Standard Fading Hours

„

The more frequently such checks are made the greater will

be the assurance that the lamp is performing satisfactorily.

The paper was made in the National Bureau of Standards

paper mill and was dyed with the direct azo dye, Benzo

Azurine G, Colour Index No 0 24l40. The dyed paper is supplied in pieces 2-5/8 inches by 3-1/4 inches 0 The booklets contain six strips of the paper 1-1/2

inches wide that have been faded by exposure in the National Bureau of Standards Master Lamp [1] in amounts corre- sponding to stated numbers of "Standard Fading Hours" of

exposure between 7 and 25. Twenty "Standard Fading Hours"

of exposure is approximately equivalent in fading action to 20 clock hours of exposure in the well-known Atlas Electric

Devices Company's FDA-R Fade-Ometer } based upon the average

2
results of tests in one hundred and thirty of these lamps

„

The paper and booklets make it possible to translate

clock hours of exposure in lamps to "Standard Fading Hours"

(SPH) and thus to express the dosage of radiant energy on

a common basis.

Given the same current^ voltage^ other electrical operating conditions 5 and similar carbons , the radiant flux

emitted by the carbon-arc fading lamp is assumed to be

reasonably under control with respect to spectral distribution o The use of the light-sensitive paper is intended

to correct for moderate variations in radiant flux.

NBS Standard Lamp

The Master Lamp at NBS is an Atlas Electric Devices

Type SMC-R enclosed carbon arc Fade-Ometer operated on alternating current and uses No. 70 solid carbons and No„ 20

cored carbons. The solid carbon is placed in the upper

holder and the cored carbon in the lower holder for one run 5 and these positions are reversed for the next run Q The arc is enclosed with a special Pyrex glass globe

No. 9200 PX 0 The lamp is operated at a black panel temperature of 150 + 5 °F (66 + 3

0 C) measured on the sample

rack a and at a relative humidity of approximately 30$, and

air temperature of approximately 116 + 1 °F (^7 + 0 o 5

0 C) s both measured at the point where the air leaves the test

chamber o The sample rack is 20 inches in diameter 5 and

rotates at approximately 3 rpm [1]„

Commercial fading lamps usually provide some control

of temperature and relative humidity of the air about the

specimens o The method of the American Association of Tex3

265-522 O - 67 - 2
tile Chemists and Colorists calls for exposure of specimens

in filtered air of 30$ relative humidity. The recommended

temperature , measured with a special black panel thermometer facing the arc, is + 5 °F (63 + 3 °C) [2] 0 2. EXPOSURE OF PAPERS

Limitations of Papers

The many factors that may affect the duplicability of

results in testing textiles for colorfastness to light make

such tests difficult to repeat. Some of the factors that

the operator of a fading lamp should keep in mind include:

density and spectral distribution of the incident radiant

flux j the temperature and relative humidity of the air at

the specimen, atmospheric contamination, method of mounting

the specimen, and intermittent exposure. These factors

affect the fading of the paper as well as textiles, but the

magnitude of the effects may not only be different for

paper and textiles but also for different textiles. The

relative rates of fading of different textiles and the paper

will not necessarily change to the same degree with changes

in these conditions 0 Exposures made on the 30-in diameter sample rack of a Weather-Ometer, using No, 20 and No. 70 carbons, will probably be much lower than are those obtained on the 20-in

diameter rack of the NBS Master Lamp, and the above factors

will not be applicable,, Also, the necessity of turning the

Weather-Ometer spray off during exposures produces conditions

that are not representative of normal Weather-Ometer operating conditions.

4
Similarly, because of differences in spectral distribution and intensity of the carbon arc, exposures made with

another type lamp such as a Xenon lamp, S-l Sun lamp, or fluoroescent lamp, will be quite different from the exposures of the Master Lamp, and the reflectance versus Standard Fading Hour curve shown in the attached figure will

not apply. The paper has been calibrated only for carbon

arc Fade-Ometers

.

The paper and some textiles fade more in a given time

if exposed intermittently than if exposed continuously,

perhaps because of an increase in moisture content while

the lamp is shut off and more rapid fading when it is

turned on again 0 It is therefore desirable to begin tests

with a fresh set of carbons in the lamp and to avoid shutdowns . Procedure for Exposure

Mount a piece of the unexposed paper in a specimen

holder of the lamp in the usual way (without backing) and

place it in the lamp at the time it is started with a new

set of carbons o Expose the paper continuously for 20 hours.

Remove it and allow it to stand in the dark at room temperature for at least 2 hours in order for it to cool and to come to equilibrium with the moisture in the air. If the

fading is to be judged only visually, trim off and discard

the unexposed edges of the paper and of the strips in the

booklets as they may affect the judgment of the fading.

For instrumental measurements the edges should remain at- tached for enhanced ease of handling during the measurements o

5
Some variations in exposure may be encountered at different positions around the sample rack. A more representative value for the lamp may therefore be obtained by

filling the circumference of the rack with paper in the

lower portion of the type CD-LSR holder when it is mounted

on a rack where it is held at only one elevation with re- spect to the arco On other types of racks , the paper

should be held at an elevation as near the level of the

center of the arc as possible and at sample distance from

it 0 From these exposures an average value for the lamp

may be obtained. The paper should be placed in the holders

so that the portion to be exposed is not backed by printed

matter on the other side of the paper. This could seriously affect the results, especially if reflectance measurements are made.

The practice in some laboratories of mounting specimens

on black or white cardboard or other backing has an effect

on fading especially of thin translucent specimens , and

therefore the backing used should be noted in reporting the

results of tests. As already indicated, the light-sensitive

paper should be exposed without backing as the SFH scale is

based upon its use in this way e For strict control, the

paper and textile should be put in the lamp at the same time and in comparable positions; for instance, both in the

upper or lower row, and any vacant positions in the lamp

should be filled with dummy specimens to reduce variations

in air currents and reflections.

6
3. RATING- OF THE PAPERS AFTER EXPOSURE

Visual Estimation

Compare the fading of the exposed paper with that of

the standard faded strips in the booklet. To do this, hold

the booklet in one hand, allow the pages to flip open one after another, rear cover first, and slip the exposed paper

under one standard faded strip after another, being careful

to have the standard strip superimposed closely upon the

exposed paper and with the long dimension of the two papers

in the same direction. Make the comparison in the light

from a daylight fluorescent lamp, or equivalent source, with

illumination of 50 foot candles or more on the papers. The

lamp should be parallel to the long edge of the paper and

booklet. The incident light should strike the paper at an

angle of 45° > and the angle of viewing should be perpendicular to the surface of the paper. Avoid touching the

surfaces of the exposed paper and the standard strips with

the fingers, as they are sensitive to moisture and soil

easily.

From the comparison, estimate the exposure in Standard

Fading Hours that would duplicate the fading of the test

piece. Obtain a factor for converting clock hours of ex- posure in the machine to Standard Fading Hours „ For example, if the paper exposed for 20 clock hours faded to an extent considered to fall half way between the 16 and 20 SFH

strips in the booklet, i.e., 18 SFH, the factor would be

18/20 or 0.9. Credit textiles exposed in the machine for a given number of clock hours with an exposure in Standard

Fading Hours of 0.9 times the clock hours

„

7
If the factor is greater than 1.1, the fading rate of

the lamp is considered too high. The lamp should then be

adjusted to a slower fading rate 0 The lamp calibration outlined in the preceding paragraphs is a suitable basis for timing exposures in routine

testingo For more precise testing, however, the dosage of

radiant energy should be measured with the paper during each

test, as the fading rate of a lamp may change from day to day and even during a test. The procedure is illustrated

by the following directions for control of a 20-hour exposure. Place the textile specimen and two (or more if desired)

pieces of the paper in the lamp at the same time, side by

side. Remove one of the papers from the lamp about 4 hours

before the estimated end of the test, noting the time.

Allow this paper to stand in the dark at room temperature

for 2 hours; compare the fading with that of the standard

faded strips; and obtain the factor for converting clock

hours to SFH as already outlined. Use this factor in

calculating the time of exposure for the textile under test. The piece of paper left in the lamp with the textile will

have received the same radiant-energy exposure as the tex- tile at the end of the test. The actual exposure in SFH

at the end of the test will then be obtained by rating the

fading of this paper with the standard faded strips in the

booklet. The result can be used as evidence that the test

was satisfactory or that it must be repeated.

For long exposures, a succession of papers will have

to be used and the number of Standard Fading Hours shown

by them added together to obtain the total exposure. In

8
carrying out such tests the paper should be changed with

each change of carbons.

In making preliminary comparisons of faded papers and

standard faded strips, it is permissible to breathe on the

faded paper momentarily to increase its moisture content.

Final comparisons should be made as already indicated, or better, after conditioning the paper in the dark by exposure to air at 50$ relative humidity overnight or longer.

Measurement of Fading by Reflectance

Although the paper and booklets are designed for simple visual estimation of the fading without the use of any

instruments, reflectance measurements with any one of

several different instruments may be used. This is done

regularly at the National Bureau of Standards in evaluating

the faded strips that go into the booklets.

The specimens are conditioned in the dark by exposure

to air having a relative humidity of 50 + 4$ and temperature

of 73.5 + 2 °F (23 + 1 °C) for not less than 16 hours. The

number of SFH corresponding to the reflectances of the

papers in the booklets sold by the NBS falls within one- half Standard Fading Hour of that indicated in the booklet.

The fading curve for light-sensitive paper, Standard Reference Material 700b, and limits of reflectance of the faded

pieces in a typical booklet are shown in the attached

figure. The papers may change in reflectance from exposure

to air of lower or higher relative humidity, or temperature,

light, soiling, and mishandling.

Reflectance measurements on different instruments

sometimes show appreciable variation even when measuring

9
the same piece of exposed paper,. Variation in reflectance

readings can be caused by such things as differences in

in linearity of photometric scales , spectral sensitivity

of the photocell, spectral transmittance of filters,

geometry of incident and viewing light beams , and differences in the plaques used to standardize the instruments.

To minimize discrepancies attributable to measuring instruments, users should construct a fading curve for the lightsensitive paper, based on reflectance measurements with

their own particular instrument, as described later. To minimize instrument error, an additional package

of unexposed paper should be obtained and set aside for

standardization use. Protect the paper from light, dust,

and excessive heat. Unexposed paper, Standard Reference

Material 700b, has been found to have an average luminous

reflectance factor Y of 0.l6ll,

To standardize the instrument, set it to read luminous

reflectance factor Y for daylight with the green tristimulus

filter. Place a piece of unexposed paper on the instrument

and set the instrument to read 0.l6ll.

An alternative method of standardization, which may

be better because it provides standardization at a level

of reflectance more nearly that of the exposed papers

measured, would be to use one of the papers in the booklet

of standard faded strips for a standard, and to set the

instrument at the value of reflectance written on the paper.

In order to avoid using paper regularly for standardizing

the instrument, read the value of a porcelain plaque

(preferably of about the same reflectance) relative to that

of the unexposed paper or relative to the booklet paper

10
used as a standard „ From then on, the plaque can be used

for setting the instrument scale by using the Y value thus

obtained. Most accurate results will be obtained if the

spectral reflectance of the plaque is nearly the same as that of the paper. With the instrument thus standardized

the papers in the booklet should be measured and a fading

curve established for the instrument 0 For most consistent

results make all measurements with the grain of the paper

in the same direction. The procedure is as follows:

1. Record the reading of 45° 0° luminous -directional

reflectance factor Y written on the face of each strip

of paper in the booklet.

2. Read the corresponding value of SFH from the table 3 or from the curve constructed from this table. Linear

interpolation may be used.

3. Measure luminous reflectance factor Y of each of

these strips on the same instrument that is to be used to measure faded strips from the Fade-Ometer.

4. Plot a curve of the measured value of luminous

reflectance relative to actual values of SFH determined

above to provide a fading curve for the user's reflectometers

•

Some reflectometers have a measurement precision that

permits reflectance to be read to four figures 3 as indicated

on the curve and in the table. Reflectance measurements,

however, are probably accurate to no better than about

0.002 or roughly to + 1 SFH at the upper end of the fading

scale and to + 0.6 SFH at the lower end.

11
4. PROCEDURE FOR ORDERING PAPER AND BOOKLETS

Different issues of the light-sensitive paper have

different fading rates , and the booklets of standard faded

strips and the fading curve supplied for any one issue of

unexposed paper apply to that issue only; therefore booklets

and unexposed paper of the same issue should be used together. The lower case letter at the end of the standard sample

number indicates the issue of the standard sample „ The

booklet of standard fading strips No„ 701b should be used

with unexposed paper No. 700b 0 It cannot be used with

No. 700a or any earlier issue of the paper . However, when

the supply of unexposed paper No. 700b at NBS becomes ex- hausted, a new issue will be supplied as Standard Reference

Material 700c. It will then become necessary for the

customer to order a new booklet of standard faded strips

No. 701c to be used with the new issue of paper. This is

unavoidable because it is not possible at present to con- trol the manufacture of the paper so that all of the issues

of paper are exactly the same with regard to fading rate. The unexposed paper cannot be used satisfactorily

without the booklet of standard faded strips because of

differences in measuring instruments , as outlined earlier.

This publication, explaining the use of the paper and booklet, accompanies each order for a booklet of standard

faded strips or paper. However, it will be sent separately,

free, on request. Order by Standard Reference Material

number (700b for the unexposed paper ; 701b for the booklet

of standard faded strips.) Address orders to

12
Office of Standard Reference Materials

National Bureau of Standards

Washington,, D.C 0 20234

Attention: Standard Reference Materials Unit

Prices and terms of purchase are given in NBS Miscellaneous

Publication 260, "Catalog and Price List of Standard Reference Materials Issued by the National Bureau of Standards."

5 o REFERENCES

[1] The original master lamp described in NBS Research

Paper RP1916, (J. Res» NBS 4l, 169-177, 1948) has

been replaced by an Atlas Electric Devices Company

Fade-Ometer, type SMC-R with glass-enclosed arc operating on 15-17 amperes , 120-145 volts alternating

current

[2] 1966 Technical Manual of the American Association of

Textile Chemists and Colorists 42 , Standard Test Method

16a-1964 5 AATCC, National Headquarters, Research

Triangle Park, P.O. Box 886, Durham, North Carolina

27702.

13
TABLE OF LUMINOUS REFLECTANCE FACTOR Y AS MEASURED

ON A GARDNER-TYPE COLOR-DIFFERENCE METER MODEL C-l vs SFH

FOR LIGHT-SENSITIVE PAPER

STANDARD SAMPLE NO. 700b

SFH X OX" XI vX or xl v

6 R .2040 1? 0 .2230 iq k 24o^

7 0 .2056 1*3 R .2244 P4l R 7 R .2070 14 .0 .2258 20 R .2428

8 o .2084 PP7P C. JL. . W

8 R .2100 1R 0 .2285 21 R .2452

Qy • 0^ .2114 P2QQ 22 .0 .2463

9.5 .2129 16.0 .2313 22.5 .2475

10.0 .2144 16.5 .2327 23.0 .2486

10.5 .2159 17.0 .2339 23.5 .2497

11.0 .2173 17.5 .2351 24.0 .2509

11.5 .2188 18.0 .2365 24.5 .2521

12 o 0 .2201 18.5 .2378 25.0 .2532

12.5 .2216 19.0 .2390 25.5 .2544

To facilitate as sembling the booklet!:3, a paper whose

flectance falls exactly on a 1/2 SFH point is given to the

next whole SFH higher. For example, if a paper happens to have

a reflectance value of .2403 it is designated 20 SFH in the

booklet; likewise, .2327 the value for 16.5 SFH is designated

17 SFH.The booklets of standard faded strips are made in three

series as follows:

7 _ 9 _ 11 _ 15 - 19 - 23 SFH

8-10-12-16-20-24 SFH

9-11-13-17-21-25 SFH

This was done for ease in visual judgment, and to facilitate

production. These booklets are considered to be equivalent,

and the one that a customer receives depends on what is

available at that time.

14


Announcement of New Publications on Standard Reference Materials

Superintendent of Documents

Government Printing Office

Washington, D. C. 20402

Dear Sir: Please add my name to the announcement list of new

publications to be issued in the series: NBS Miscellaneous

Publication 260 - Standard Reference Materials.

Name

Company

Address

City State Zip Code

(Notification key N-330)


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