Tears in canvas. Glue a patch of matching canvas to the inside with Devcon Patch. See
canvas.
Tears in rubber or rubberized material. Clean surface and let dry. Cut a patch from the bottom of the curtain. Coat curtain and patch with rubber cement. Let dry. Apply a second coat to patch and press in place.
Tears in oiled silk. Cover with cellophane tape.
Tears in plastic. Cut a patch out of matching plastic material and glue down with plastic-mending adhesive.
Mildew stains. Brush stains with strong detergent solution. Hang curtain out to dry.