The Bondo Shower & Tub Kit from 3M was designed to permanently repair small chips, scratches, cracks gouges and holes in fiberglass, porcelain and acrylic tubs, showers, sinks, hot tubs, pools and boats. According to the manufacturer, the product may be used for marble and ceramic repairs as well. Bondo Shower & Tub Kit should be used on white or almond surfaces only if a perfect match is desired.
Remove protruding chips from the repair area using a utility knife. Sand with medium grit sandpaper to level the surface. Clean with nail polish remover to eliminate soap scum, oils and wax residue from the sandpaper.
Pour polyester resin into the mixing container provided with the Bondo shower & Tub kit. Refer to the proportions guide to determine the necessary amount for your repair size. Mix in white or brown colorant to tint the mixture to the color of your repair area.
Mix in thickener and add Hardener according to the Bondo repair kit instructions. Too much hardener will cause the product to set quickly; too little will prevent hardening. If unsure, mix a test batch before proceeding with the actual repair.
Mix the ingredients thoroughly. You now have 10 to 15 minutes to complete the repair before the Bondo Shower & Tub mixture hardens. Coat the repair area using the flat applicator. Press the mixture in. Level it until the surface is slightly higher than surrounding areas.
Wait two hours. Sand the area, beginning with medium grit and progressing to fine sandpaper. Mix a second bath of resin, colorant and hardener without thickener and brush over the repair using a Q-tip or small painter's brush. Once hardened, sand with the finest sandpaper.
Buff the repair with the buffing compound to match the gloss of surrounding areas.
For holes and large cracks apply the reinforcing mesh provided with the Bondo Shower & Tub Kit before beginning the repair.