MIL-PRF-24635E
4.5.12 Spraying properties. The coating shall be sprayed onto a test panel prepared in accordance with 4.4.1.
The panel shall be observed for spraying properties in accordance with Method 4331.2 of FED-STD-141.
4.5.13 Sag resistance. The sag resistance of the coating shall be determined in accordance with ASTM D4400.
4.5.14 Drying times. The set-to-touch and dry-through times shall be determined in accordance with
ASTM D5895.
4.5.15 Contrast ratio. The contrast ratio of the fully cured coating shall be determined in accordance with
ASTM D2805.
4.5.16 Color testing.
4.5.16.1 Instrumental color deviation determination. Test specimens shall be prepared in accordance with
ASTM D823 Methods C or E using a nominal 0.006-inch blade film applicator onto a clear plate glass of not less
than ⅜-inch (nominal) thickness that has been ground to a uniform finish with 1F carborundum. A standard black
and white Leneta chart is also acceptable. The color deviation shall be determined in accordance with ASTM
D2244 using an instrument having a D65 light source, a 45-degree illumination angle, and a 0-degree viewing angle.
The instrument shall be demonstrated to read the color of National Institute for Science and Technology (NIST
[formerly National Bureau of Standards (NBS]) traceable standards. After calibration of the instrument, the L, A, B
color values, of at least two FED-STD-595 color cards, shall be measured of the color being procured which were
received from the Government not greater than 1 year prior to the date of this use. Delta E shall be calculated for
each color card. The mean values of E, L, A, and B shall be determined for the color cards. These mean values will
be used to calculate the color difference values. The color values of the test coating shall be measured immediately
after mixing in accordance with the manufacturer's instructions. The color deviation terms shall be calculated. If
using an instrument that automatically calculates the color differences, the color card mean values shall be entered as
the base line for the color difference calculations.
4.5.16.1.1 Referee color matching. If the coating measured in accordance with 3.5.16.1 does not match the
color card when visually examined, the discrepancy shall be resolved by an independent laboratory certified to the
NIST National Volunteer Laboratory Accreditation Program for paint testing.
4.5.17 Gloss. The thoroughly mixed coating shall be applied to a standard black and white Leneta chart in
accordance with ASTM D823. A film applicator shall be used that will produce a WFT of 0.151 mm (0.006 inch).
Allow to cure to service in accordance with the manufacturer's ASTM F718 sheet under referee conditions in a dust
free environment. Paint specimen shall be dry hard before gloss test. A longer cure time may be used if necessary
to meet the gloss requirement of this specification. The 60-degree specular gloss of the fully cured coating shall be
determined in accordance with ASTM D523.
4.5.18 Solar reflectance. A reflectometer capable of measuring reflectance at specific wavelengths shall be
used to measure the visible and Near IR reflectance of the test cards produced in 4.5.17. Measurements shall be
made at the wavelengths specified in 3.5.18, similar to figure 2. Test results shall be in accordance with the
requirements of 3.5.18. A Diano Hardy Match Scan II equipped with a Milton Roy Diano Match Pak II has been
found satisfactory for measurements at 800 ηm and 1000 ηm. Other instruments of equivalent capability may be
used.
4.5.19 X-cut or cross-cut adhesion. Two panels shall be prepared in accordance with 4.4.1. The coatings shall
then be applied and allowed to cure to service in accordance with the manufacturer's ASTM F718 sheet. For
coatings with a manufacturer's recommended total system dry film thickness (DFT) greater than 15 mils, X-cut
adhesion shall be determined in accordance with ASTM D3359, Method A. For coatings with a manufacturer's
recommended total system DFT of less than 15 mils, cross-cut adhesion shall be determined in accordance with
ASTM D3359, Method B. If the total DFT is between 5 to10 mils, the spacing between the lines in the Method B
cross-hatch shall be doubled. If the total DFT is between 10 to15 mils, the Method B line spacing shall be tripled.
4.5.20 Overcoat adhesion. Ten test panels shall be prepared in accordance with 4.4.1. The ten panels shall
then be overcoated and tested as follows:
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