1、 FORD LABORATORY TEST METHOD BI 009-02 Date Action Revisions 2001 03 13 Revised Editorial no technical change A. Cockman 1992 06 10 Printed copies are uncontrolled Page 1 of 5 Copyright 2001, Ford Global Technologies, Inc. COLOR EVALUATION OF PAINTS Application This procedure is used to measure smal
2、l differences encountered in color matching of paints and in color fastness evaluation. Scope This procedure employs the use of a tristimulus filter colorimeter. The spectral responses obtained closely approximate the C.I.E. tristimulus specifications of Illuminant C (Standard Artificial Daylight),
3、thus the readings of the instrument and the derived color differences correlate with visual judgment made in average daylight. Apparatus Required Colorimeter* A “Colormaster“ differential colorimeter is used to measure the color of paint when applied to steel panels. Three filters - green, red and b
4、lue - are supplied with the instrument. The reflectance or transmission readings obtained successively through each of the filters are labeled G (green, R (red) and B (blue). G and B are proportional to C.I.E. tristimulus values, Y and Z respectively, of the sample measured. The transmission of the
5、red filter closely matches the red portion of the C.I.E. value “X“ and the blue component is obtained as described in the Adams Coordinate Manual supplied with the instrument. This instrument may be obtained from the Meeco Instrument Mfg. Co., Hatboro, PA. Two white glass standards are provided with
6、 the instrument. The calibration values of G, R and B are marked on the back of these standards. The standards should be kept clean by occasionally washing with soap and water. Equivalent apparatus may be used which will provide the tristimulus values X, Y and Z as indicated above. FORD LABORATORY T
7、EST METHOD BI 009-02 Page 2 of 5 Copyright 2001, Ford Global Technologies, Inc. Conditioning and Test Conditions All test values indicated herein are based on material conditioned in a controlled atmosphere of 23 +/- 2 C and 50 +/- 5 % relative humidity for not less than 24 h prior to testing and te
8、sted under the same conditions unless otherwise specified. Procedure Standardization of Instrument 1. Place a white glass standard over the sample and reference ports of the instrument. 2. Set the reflectance control to read the “G“ value of the white glass standard over the left hand or sample port
9、. Set the green control to the middle of its range (1 1/2 turns from end). Turn the filter switch to “G“. Adjust the Zero control to make the meter read zero, making the final adjustment with the sensitivity switch depressed for high sensitivity. 3. Turn the filter switch to “R“ and set the reflecta
10、nce control to read the “R“ value of the white glass standard. Set the red control to make the meter read zero, making the final adjustment with the sensitivity switch depressed for high sensitivity. 4. Turn the filter switch to “B“ and set the reflectance control to the “B“ value of the white stand
11、ard. Set the blue control to make the meter read zero, making the final adjustment with the sensitivi ty switch depressed for high sensitivity. Note: The above controls should not be disturbed further, except when standardization is being rrepeated. 5. Sensitivity Check With the white standards on t
12、he sample and reference ports and the instrument standardized as in Steps 1 through 4, check the sensitivity by determining the number of meter divisions that correspond to a change in reflectance dial reading of 0.1 %. Sensitivity should be at least as large as the values below: G R B Sensitivity U
13、a/0.1 % 5 3 3 FORD LABORATORY TEST METHOD BI 009-02 Page 3 of 5 Copyright 2001, Ford Global Technologies, Inc. Sample Measurement 1. Remove the white glass standard from the left hand or sample port and replace it with the painted panel prepared as specified by the material standard or Engineering s
14、pecification. Note: For color matching, use the standard size opening. For water and soap spotting tests, a standard adapter with an approximately 3/8 inch opening is used over the sample and reference ports because of the small area tested. 2. Turn the filter switch to “G“ and adjust the reflectanc
15、e control to make the meter read zero and refine the adjustment with the sensitivity switch depressed. Record the reading of the reflectance dial as “G“ for the sample. 3. Turn the filter switch to “R“ and determine reflectance value as in Step 2. Record as “R“ for the sample. 4. Turn filter switch
16、to “B“ and measure reflectance value “B“ for the sample as in Step 2. 5. Return filter switch to “Off“ position after each set of measurements to keep the glass color filters cool and improve stability. Note: This test method shall also be used to measure tristimulus values for maintenance paints. D
17、etermination of N.B.S. Units When color differences are specified in N.B.S. units, the following calculations are necessary. The individual steps are described in detail below and are illustrated in the form of a data sheet shown in Exhibit A. The color co-ordinate tables which are required for thes
18、e computations are supplied with the instrument. In addition, a color difference slide rule may be helpful in shortening the calculations. 1. Enter the green, red and blue reflectances read from the colorimeter as Items 1, 2 and 3. 2. Multiply Item 2 by 0.8. Record as Item 4. 3. Multiply Item 3 by 0
19、.2. Record as Item 5. 4. Add Items 4 and 5. Record as Item 6. 5. Find Item 1, G, in Column 1 of the color coordinate table. Read L opposite it in Column 2 and record as Item 7. Read aG in Column 3 and record as Item 9. Read bG in Column 4 and record as Item 10. 6. Find Item 6, R, in Column 1 of the
20、table. Read aR in Column 3 and record as Item 8. 7. Find Item 3, B in Column 1 of the table. Read bB in Column 4 and record as Item 11. FORD LABORATORY TEST METHOD BI 009-02 Page 4 of 5 Copyright 2001, Ford Global Technologies, Inc. 8. Subtract Item 9 from Item 8 and record as Item 12. 9. Subtract I
21、tem 11 from Item 10 and record as Item 13. Determination of the Total Color Difference The total color difference, E, may be determined by measuring or computing the straight line distance between two points in the visually uniform color-space. It is computed from the individual color coordinate dif
22、ferences, thus: Chemicals, materials, parts, and equipment referenced in this document must be used and handled properly. Each party is responsible for determining proper use and handling in its facilities. FORD LABORATORY TEST METHOD BI 009-02 Page 5 of 5 Copyright 2001, Ford Global Technologies, I
23、nc. CALCULATION OF COLOR COORDINATES FROM DIFFERENTIAL COLORIMETER DATA Sample No. Item 1 2 3 4 5 1. G 32.92 32.34 32.92 32.56 32.62 2. R 32.51 32.55 32.36 32.37 32.20 3. B 29.45 25.55 30.56 28.54 29.52 4. 0.8 R 26.01 26.04 25.89 25.90 25.76 5. 0.2 B 5.89 5.11 6.11 5.71 5.90 6. (4) + (5) = R 31.90 3
24、1.15 32.00 31.61 31.66 7. L 62.40 61.92 62.40 62.11 62.16 8. aR 257.6 255.0 258.0 256.6 256.8 9. aG 261.1 259.1 261.1 259.9 260.1 10. bG 104.4 103.6 104.4 104.0 104.0 11. bB 99.6 93.6 101.2 98.2 99.7 12. (8) (9) = a -3.5 -4.1 -3.1 -3.3 -3.3 13. (10) (11) = b 4.8 10.0 3.2 5.8 4.3 14. L* -0.5 0.0 -0.3 -0.2 15. a* -0.6 +0.4 +0.2 +0.2 16. b* +5.2 -1.6 +1.0 -0.5 17. E 5.3 1.7 1.1 0.6 * Differences in L, a, and b relative to Sample No. 1.
