MIL-PRF-5425E
3.6 Optical uniformity.
3.6.1 Optical defects. The plastic sheet shall contain no optical defects, such as embedded
particles, bubbles, scratches, or imperfections, that reduce visibility through the sheet and cause a
variation in angular deviation of more than 5 minutes within a distance of not more than 20 inches
(50 cm) on a grid board when tested as specified in 4.5.12.1. Blemishes that do not individually
reduce visibility through the sheet shall be disregarded unless they form a cluster. Optical defects
within 1 inch (25.4 mm) from the edge of the sheet shall also be disregarded.
3.6.2 Angular deviation. The plastic sheet shall contain no surface irregularities which cause
angular deviations on either side of the undeviated position that are greater than the limits
specified in table III when tested as specified in 4.5.12.2.
TABLE III. Angular deviation.
SHEET THICKNESS
LIMITS OF PERMISSIBLE DEVIATION 1/
0.060 through 0.220 inch
7 minutes at any location more than 1 inch from
the edge of the sheet.
Over 0.220 through 0.250 inch
7 minutes at any location more than 3 inches
from the edge of the sheet and 9 minutes
between 3 inches and 1 inch of the edge.
Over 0.250 through 0.375 inch
7 minutes at any location more than 3 inches
from the edge of the sheet and 12 minutes
between 3 inches and 1 inch of the edge.
Over 0.375 through 0.500 inch
7 minutes at any location more than 3 inches
from the edge of the sheet and 14 minutes
between 3 inches and 1 inch of the edge.
Over 0.500 through 1.000 inch
12 minutes at any location more than 3 inches
from the edge of the sheet and 20 minutes
between 3 inches and 1 inch of the edge.
1/ Surface irregularities within 1 inch from the edge of the sheet shall be disregarded.
3.7 Instruction sheet. An instruction sheet containing information relating to the necessary
precautions to be observed in the use, forming, cementing, handling, and storage of the plastic
sheet shall be included in each shipping container.
3.8 Protective covering. A protective covering shall be applied to both sides of the plastic
sheet to protect the surfaces from scratches and abrasions. The covering shall be easily removed
without injury or damage to the surface. The plastic sheet shall be identified on the protective
covering by specification number, thickness, manufacturer's code, and national stock number.
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