The following is a full text of Colors: (for) Ready-Mixed Paints. Federal Specification TT-C-595, published on 12 January 1950, 36 pp. (including 4 pp. text, 3 pp. index, and 29 pp. containing 187 paint color deposits in the McCorquodale Process).
1. PURPOSE AND SCOPE
1.1 Purpose.-The purpose of this Federal specification is to present in convenient booklet form a collection of color spots which the various Government agencies may use in the procurement of paint and related materials.
1.2 Scope.-The paint color spots covered by this specification are intended to provide a simple, practical means of indicating paint colors. The specification describes a method for the rapid visual comparison of colors, and gives fundamental colorimetric data for correlation with systems similarly specified.
2. APPLICABLE SPECIFICATIONS
2.1.-The following Federal Specification, of the issue in effect on date of invitation for bids, forms a part of this specification:
TT-P-141-Paint, Varnish, Lacquer, and Related Materials; Methods of Inspection, Sampling, and Testing.
(Copies of Federal specifications and the Federal Specifications Index may be obtained upon application. accompanied by postal note, money order. coupon. or cash. to the Superintendent of Documents, U. S. Government Printing Office. Washington 25. D. C. Prices may be obtained from the Superintendent of Documents.
3. CLASSIFICATION AND NUMBERING SYSTEM
3.1 Description of color spots. Each spot consists of an area 2 5/8 by 1 3/4 inches, coated with a pigmented lacquer. Each spot has been assigned an identification number.
3.2 Color classification.- The color spots have been classified in three main groups depending upon the gloss of the surface finish. These three groups are designated glossy colors, semiglossy colors, and lusterless (or flat) colors. Each of the three groups is further classified according to the hue name. These colors are presented in the order brown, red, orange, yellow, green, blue, gray, and miscellaneous (including black and white). For a particular color group, the colors are arranged, when possible, in the order of dark to light.
3.3 Numbering system.-The numbering system used for the color spots is based on the arbitrary assignment of one hundred numerals to each of the eight color classification groups. In each color classification, open numbers are left between each two adjacent color spots in order to provide for additional spots to be inserted without destroying the progression of spots from dark to light This numbering system is shown in Table I.
5.2 Working specification of color. -In addition to the fundamental colorimetric specification of a collection of color samples, it is often convenient to have available the more popular, but usually less exact, specification of samples in terms of the Munsell System of Color. It is intended that a specification of a master set of color spots be made in terms of the Munsell System of Color both by the method of visual comparison and by the method of spectrophotometric analysis. From the Munsell notations thus obtained, it is intended that a less exact but useful naming of the colors be obtained by means of the Inter-Society Color Council-National Bureau of Standards (ISCC-NBS) system both from visual comparison and spectrophotometric analysis.
5.3 Gloss.- There are three general classifications of the specular component of the light reflected from the surface finishes of the paint spots. It is intended that gloss measurements be made of a master set of these color spots for an initial record.
5.4 Permanence study.-With available initial data on the master set of spots based on spectrophotometry, colorimetry, and glossimetry, subsequent redetermination may be made to study the permanence of the color spots.
5.4 Results.-The results of the colorimetric analysis of a master set of the paint spots as well as the Munsell notations, color names, and gloss determinations will appear in a supplement to this specification.
4. USE OF COLOR SPOTS FOR PAINTS
4.1 Care of color spots.-Paint colors may change upon expo-sure to strong sunlight or with age. While the colors of these spots are believed to be fairly permanent, some of them will tend to change more than others if care is not exercised in their use and storage. Exposure to strong sunlight must be avoided, and the booklet should be kept closed when not in use. Care should also be exercised that the spots do not become soiled.
4.2 Color matching.-Conformity of paint supplied to match any of these color spots shall be determined by visual comparison unless otherwise specified. The fundamental colorimetric specifications (chromaticity coordinates and luminous reflectance) are to be included to permit the color spots to be correlated with other working standards that are also specified on a fundamental basis, and to make possible a reissue of the. same colors at any desired later date.
4.3 Visual comparison of color cards.-In comparing visually the color of a paint sample with the spots shown, the sample and spot shall be placed beside each other on a table in front of a north window, so that the illumination centers on an angle of about 45° and the viewing is nearly normal to the surfaces compared. To prevent appreciable quantities of extraneous light from reaching the samples, it is suggested that nearby bright walls and ceilings be covered with black cloth, and that all other lights in the room be turned off. A black ceiling cover is necessary for comparison of glossy specimens because of mirror reflection. In order to exclude all adjacent colors from view, place a piece of neutral gray paper with an opening cut in the center over the sample and spot. One-half of the cut-out portion of the mask should be placed over the sample and one-half over the spot.
5. COLORIMETRIC ANALYSIS AND PERMANENCE STUDY
5.1 Fundamental specification of color.-Most material working standards for color are specified on a fundamental basis, using the present-day methods for the engineering description and specification of color. It is intended that a spectrophotometric and colorimetric analysis of a master set of these paint color spots be made by the Photometry and Colorimetry Section of the National Bureau of Standards. The paint spots thus expressed in fundamental terms may be correlated with material working standards in systems of color, collections of color samples, or specification for color. This fundamental analysis also will serve as a guard against color drift in any reissue of the paint spots.
6. STANDARDIZATION AND TEST PROCEDURES
6.1 Spectrophotometry. -The spectrophotometer shall be recognized as the basic instrument in the fundamental standardization of color.
6.2 Standard observer.-Color specifications computed from spectrophotometric data shall be found by means of the standard observer and coordinate system adopted in 1931 by the International Commission on illumination.
6.3 Standard illuminant C.-In the absence of a special reason for adopting some other illuminant in reducing spectrophotometric data, standard ICI illuminant C, representative of average daylight, shall be used.
6.4 Daylight reflectance and chromaticity coordinates.-The basic specification of color shall consist of the daylight reflectance Y, and the chromaticity coordinates x and y, of the ICI coordinate system.
6.5 Munsell notations.-For the popular identification of color, the Munsell Book of Color may be used. Approximate identifications of Munsell hue, value, and chroma may be secured by direct visual comparison with samples in the Munsell Book of Color. When the most accurate visual comparisons are needed, the mask method is recommended. Wherever more exact Munsell notations are desired, they shall be found from the basic specification Y, x and y by interpolation among the smoothed curves for Munsell hue, value, and chroma.
6.6 ISCC-NBS color names.-A descriptive name according to the ISCC-NBS system of color designation may be derived from the Munsell notation. This name is recommended wherever general comprehensibility is desired and precision is not important. The use of color names for color specification is not recommended.
6.7 Determination of gloss.-To determine the gloss of surface finishes, method 610.1 of Federal Specification TT-P-141, Paint, Varnish, Lacquer, and Related Materials; Methods of Inspection Sampling, and Testing, shall be followed.
7.1 Separate color chips.-For reasons of economy and convenience it is planned to make all colors of this booklet available in the form of individual color chips.
7.2 Source of paint colors.-Many of the paint spots have appeared previously in the U. S. Army Specification No. 3-1, Color Card Supplement, revised April 21, 1943. In addition to these Department of the Army colors, this booklet includes paint colors used by the Department of the Navy, the Department of the Air Force, the U. S. Maritime Commission, the Veterans Administration, the Panama Canal, the Post Office Department, the Department of Agriculture, the Department of Commerce, the Department of Interior, the Department of Justice, the Public Buildings Administration, the Civil Aeronautics Administration, the U. S. Coast Guard, the U. S. Marine Corps, and other Government departments and agencies. By common agreement among these Government activities, near replicas of many colors have been avoided and a consequent reduction effected in the total number of colors included.
7.3 Inspection procedure.-As a matter of record the inspection procedure by means of which duplication of the desired colors was assured is given here.
7.3.1 Color tolerances.-The color tolerance specification was based on the NBS (National Bureau of Standards) Unit of Color Difference defined by Equation 13 of NBS Circular C429, Photoelectric Tristimulus Colorimetry with Three Filters, by Richard S. Hunter, July 30, 1942. Equation 13 gives in NBS units the size of the difference, ΔE, between two colors of tristimulus specifications: Y1, α1, β1 and Y2, α2, β2, and may be written as follows:
and K0 is taken as zero for lusterless spots, 0.010 for semigloss spots, and 0.025 for gloss spots. Y is the daylight directional reflectance of the spots, and (α, β) are the chromaticity coordinates. The NBS unit of color difference is intended to be so small that color differences of less than one unit will be perceptually unimportant in most commercial transactions. This unit is about three or four times the smallest color difference perceptible with certainty under the best conditions of observation by a trained inspector. One NBS unit corresponds approximately to 0.10 Munsell value step, to 0.15 Munsell chroma step, and to 0.25 Munsell hue step at chroma/10, or to 1.25 Munsell hue steps at chroma/2.
7.3.2 Preliminary inspection.-The contractor was supplied with a set of master standards obtained from the Government agencies listed above (7.2); a duplicate set of master standards was retained at the National Bureau of Standards. The contractor was required to submit for approval samples of the color spots that he expected to deliver. For the colors in this booklet, three inspectors consisting of the Chairman of the Technical Committee on Paint, Varnish, Lacquer, and Related Materials, Federal Specifications Board; the Subcommittee Chairman on the Color Card; and the Technical Assistant to the Technical Committee, compared visually by natural daylight the colors on each completed sheet (maximum of 12 color spots to a sheet) with the respective master standards (duplicates of the unmounted paint chips supplied to the contractor). Any color spots judged by one or two (but not all three) of the inspectors to be unsatisfactory duplicates of the desired colors or unsatisfactory in gloss were referred by the inspectors to the Photometry and Colorimetry Section, National Bureau of Standards, for test.
In these tests the color tolerance specification was based on the NBS (National Bureau of Standards) Unit of Color difference (see 7.3.1). Each sample submitted by the inspectors was compared with the master standard by using 45-degree illumination and perpendicular viewing (or the equivalent), and by using Macbeth (6800 degrees K) daylight. Samples differing from their respective master standard by two (2.0) NBS units of color differences or less were approved except for the following colors:
For these twenty-five colors, approval was mandatory only if they were found to differ from their respective master standards by 1.0 NBS unit or less.
The gloss tolerance was based upon method 610.1 of Federal Specification TT-P-141, Paint, Varnish, Lacquer, and Related Materials; Methods of Inspection, Sampling, and Testing. The sample submitted for test by the inspectors was approved if it satisfied the following requirements: Lusterless, maximum of 6, Semigloss, 30 to 50, Gloss, minimum of 85.
Even if a color spot was found not to comply with the color and gloss requirements, the inspectors could approve it on their own judgment or after consultation with representatives of the agencies using paint of that color. However, the inspectors could also disapprove a color spot without requesting a test of the offending’ color; but in this case the contractor could demand a test of it.
7.3.3 Final inspection.-The final inspection of the booklet (Federal Specification TT-C-595) was made at the contractor’s plant by the three designated inspectors. Five samples were taken at random from each’ one thousand units and inspected.