Fiberglass tubs are normally durable, long-lasting and have very low maintenance cost. They might develop cracks when exposed to mechanical strain or can even break if the force they are subjected to is too strong. However, repairing a fiberglass at home is not a Herculean task because the fine fibers of spun glass can be mended easily. All you need to do is, purchase a repair kit from the market and follow the instructions to fix it.
Repairing a Fiberglass Tub
Step 1: Purchase a Fiberglass Repair Kit
Buy a fiberglass repair kit from the market. Check that the kit contains all the materials required for repair. Repair kits usually contain polyester resin, hardener (to harden the resin), colorants, fiberglass mesh or mat (for heavy repair), coarse and fine sandpaper, thickener (to stiffen the resin when applied vertically), container for mixing, stirring tools, and protective chemical resistant gloves. You will need all these materials and tools while repairing the tub.
Step 2: Analyze the Nature of the Damage
A fiberglass can develop cracks either on the surface or they can be embedded deep inside. You will require a fiberglass reinforce cloth to fill a surface crack. This provides better support and the fiberglass lasts for a longer time. If the cracks are deep, then you need to fill the hole from the top with layers of tape. This means you have to begin working from the top and then move to the underside. Thus, depending upon the nature of the damage, you choose the repair technique.
Step 3: Clean and Dry the Damaged Area
You must clean the damaged portion before applying chemicals on it. Therefore remove dirt, grease, wax, soap, oil, chips, and scum from the broken area. Smooth the broken edges with a metal file or with the sandpaper. Remove the broken pieces or file off the protruding edges. Then wash off the dirt with water, followed by acetone. Blow dry the cleaned surface with a hair dryer.
Step 4: Cut the Cloth or Prepare the Tape
As already said, you will have to use a fiberglass reinforce cloth or a mesh to repair surface damage. So measure how much cloth you need to fit in the damaged area and then cut it in patches. For minor damages you can fill it with the repair resin. Start placing layers of tape in the topmost portion of the hole, if it's substantially deep. Then proceed to the bottom or the underside of the tub. Make sure that the hole or the crack is free from dust and broken particles.
Step 5: Prepare the Solution of Resin
Pour the resin in the container as per the volume mentioned in the kit. Add the colorants and the thickening agent that came along with the tube. Adding thickener prevents the liquid from dropping. Mix the colorants in appropriate amount to get the color of your choice and then remix with resin. Some common colors include milky white, almond, pink, dark brown, etc. Stir the contents until the resin becomes opaque. Check if the color matches perfectly with the original color of the fiberglass tub or else adjust the composition.
Step 6: Add the Hardener to the Resin Mix
Check how much quantity needs to be added from the repair manual. Now mix the hardener in appropriate proportion with the epoxy resin colorant mixture. If the quantity of hardener you have added is not sufficient, then the resin won't solidify and will remain tacky.
Step 7: Fill the Cracks Properly
Soak the patches of reinforcing cloth immediately in the epoxy resin mixture and stack them evenly one after another in the crack. Spread the resin on the patches with a blunt plastic knife. You can use a screwdriver to fix the cloth tightly. If the hole is deep and vertical, then you have to pour the resin filler in the hole while keeping the tape fixed on the top of the hole. You can also place a plywood at the bottom of the hole while pouring the high-density epoxy filler. Remove the plywood after the resin has hardened.
Step 8: Add Finishing Touches
Let the resin dry and harden overnight. Once it has hardened, you need to smooth the surface of the patches preferably with 100 grit sandpaper. Trim off the rough edges of the fiberglass cloth with a coarser sandpaper (400 grit). You can apply another layer of resin and colorant mixture without adding any thickener for a better finish. Apply it smoothly with a cotton swab or a paint brush. You can also apply a coat of tinted or transparent gel in order to add shine to the surface. Leave it overnight to dry. Smooth the repaired area with a wet sandpaper so that it blends perfectly with the whole texture.
Precautions to be Taken
Always wear the gloves provided along with the kit while working. Do not drop any chemical over undamaged sections of the fiberglass tub. Make sure you do not touch the chemicals with bare hands as they might cause irritation or burn your hand.
I'm sure you haven't found the task too daunting. Take it up as a DIY project and save the cost of hiring a mechanic to repair it. However, I would suggest you to replace the tub if its warranty period has expired and it is developing cracks frequently.
