1/2" Black Back Copper Foil 1/2" Black Back Copper Foil 1.25 mil (31 microns) Thick 1/2 IN X 36 YDS (12.7 mm X 33 M) Black coloring on adhesive (back) side of foil allows use on clear glass, etc. where a black patina is used on the soldered surface and a black finish is desired.