Bathtubs are made of many materials, including cast iron, ceramic, porcelain, copper, concrete, fibreglass and acrylic. Acrylic is combined with fibreglass, making it highly resistant to chipping and cracking. An acrylic bathtub is lightweight and cost-effective, but it may develop cracks after many years of use or if a heavy object is dropped onto the surface. Fix a crack in an acrylic bathtub as soon as possible to prevent leaks and further cracking.
Wipe down the bathtub with a wet cloth to remove any dirt.
Dry the bathtub with a clean cloth.
Follow the instructions on the fibreglass repair kit. These kits can be found at most hardware stores. A filler substance is included in the kit and often requires mixing.
Place a dab of filler on a putty knife and work into the crack. If it is a large crack, work in 2-inch sections to ensure the filler is properly applied. Allow the filler to dry for 12 to 24 hours until it is completely dry.
Smooth the area out with wet fine-grit sandpaper.
Paint over the filled crack with an acrylic paint that matches the colour of your tub. Acrylic paint can be found at most hardware stores.