The following text is a quote from MIL-I-24768 military specification for surface requirements for laminate FR4/G10/G11 sheet,rod and tube. 3.4.4 is the requirement for Surface finish, and 3.4.5 is the requirement for Surface defects.
3.4.4 Surface finish.
3.4.4.1 Laminated sheets. Unless otherwise specified (see 6.2), the surface finish of laminated sheets shall be semigloss as produced by the laminating process.
3.4.4.2 Laminated tubes and rods. Unless otherwise specified (see 6.2), tubes shall be furnished in the following finishes.
3.4.4.2.1Ground. Ground finish is applied by a fine grinding wheel or belt and is free from any pronounced scratches.
3.4.4.2.2 Buffed. Buffed finish is somewhat more glossy than the ground finish and is obtained by buffing the tube or rod immediately after grinding, using a small amount of shellac or other polishing compound on the buffer.
3.4.5 Surface defects.
3.4.5.1 Laminated sheets. Sheets shall be free from internal and external blisters, wrinkles, or cracks
and other small defects such as scratches, dents, or heat marks. If the insulation material contains a glass fabric, differential coloration of various warp or filler threads of the glass fabric or the filament of the non-woven parallel alignment fibers may cause streaks.
3.4.5.2 Laminated tubes and rods. Laminated tubes shall be free from blisters, pronounced mandrel scores, loose layers, resin pockets, voids, and heat marks. Rolled tubes shall be free from wrinkles. Molded tubes shall be free from seam cracks. Rods shall be free from blisters, mold seam cracks, voids, and resin pockets. Tubes with a wall thickness greater than 0.500 inch or rods with a diameter greater than 1.000 inch may show checks or cracks between the laminations on machined or sawed edges. Edges, drilled holes, and machined, milled or ground faces of laminated rods and tubes shall be smooth and shall present a neat appearance.
