Acrylic (they are also fiberglass) bathtubs and showers are very durable, easy to clean and look beautiful, but, nevertheless, are prone to accidental damage. Fortunately, inexpensive repair kits are available for such cases.
Steps

Step 1. Purchase a suitable bathroom (or shower) repair kit
Make sure your bathroom is fiberglass before buying, as our recommendations will not work with cast iron or other plumbing fixtures.
- You can check the bathroom material by tapping it with your knuckles or a wooden spoon (so as not to damage the outer acrylic layer). Fiberglass will give a soft, dull, non-metallic sound.
- Match the color of the repair kit to match your bathtub. Most kits have dyes in their set that allow you to change the shade of the final product and tint it to the most common colors, such as white, pastel or beige.
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Check that everything you need for the job is included in the kit, or purchase the necessary materials and tools separately. Here's a rough list of what the kit might include:
- Polyester resin
- Hardener (accelerates the hardening of the resin)
- Fiberglass mesh or cloth (for serious and deep damage).
- Dyes
- Sandpaper of various grain sizes from P80 (coarse processing) to P2500 (surface sanding)
- Thickener (for thickening the resin and working on vertical surfaces).
- Protective gloves
- Mixing container and tool

Step 2. Prepare the surface ' … Cut off any torn or protruding fibers around the damage, rub lightly with medium-grit sandpaper to remove grease, soap residues and other possible contaminants, wipe with acetone or solvent to ensure good adhesion of the bonding surfaces.

Step 3. Decide if a fabric patch is needed for the damaged surface
If not needed, skip to the section on mixing and toning the mixture. If the crack is wider than 5 millimeters, or it is generally a hole that cannot be filled with resin alone, cut out a piece of mesh or fabric slightly larger in area than the damaged area. Serious damage may require multiple layers of patch.

Step 4. Study the instructions for mixing and toning the kit you purchased
Since the various sets differ from each other in composition and quantity, please read the instructions carefully before starting work.

Step 5. Place a piece of cardboard or old newspaper on the surface where you will mix
Place the mixing container (usually included in the kit) on the cardboard.

Step 6. Measure and pour the correct amount of polyester resin into the mixing container
Most kits have a proportional amount for the mixed substances relative to their volume, for example 1/2 volume, 1/4 volume of resin with the appropriate amount of hardener.

Step 7. Add dye from the appropriate tube that came with the kit
For example, to get a beige color, mix 5 parts white with 1 part brown to 20 parts resin. For a pure white color, add white dye until the resin is completely white, opaque. Mix all the ingredients thoroughly and check the resulting color against the plumbing before adding the hardener. Step 8. Add the thickener to the resin and colorant until the mixture reaches the consistency you want to work with.
To work on a vertical surface, the mixture must be very thick so that it does not drip or run. For horizontal surfaces, the compound may be thinner, but must be thick enough to be smoothed with the applicator.

Step 9. Add hardener according to kit instructions
If you do not know the required proportion, you may have to find it empirically. Simply put, too much hardener will make the resin harden process too fast, giving you less time to work and too little time to tinker. If you add too little hardener, the resin will not cure and will remain sticky. Add about 5 drops of hardener to each tablespoon of the resin / dye mixture.

Step 10. Mix all ingredients thoroughly, grasping the corners and edges of the container to distribute the hardener evenly
The longer you stir, the better the result will be. But remember that from the moment the hardener is added, the mixture begins to solidify, and you only have 10-15 minutes before the resin hardens and becomes unusable.

Step 11. Using a trowel or putty knife, scoop up some of the mixture and apply to the damaged area
If you need to make a fabric patch, place the piece of material you cut out on top and press into the resin. Cover the top with the mixture. Make sure the surface of your patch is flat and slightly protrudes from the surface of the bathroom. Later, you will remove the protruding part with sandpaper and polish it. When the mixture is applied, allow it to harden, it usually takes about 2 hours at room temperature.

Step 12. Gently sand the patch, being careful not to scratch the adjacent surface
If the patch used mesh or fabric, trim off the protruding fibers with an edger knife before sanding. Start with a coarse or medium sandpaper, depending on which layer of putty you need to clean off so that the patch is flush with the surface of the bathtub. Then change the emery to a fine-grain emery, and then to a polishing emery ("zero"), until the surface of the patch is perfectly smooth. If you need to "build up" the patch, mix in another batch, apply, allow to harden and re-sanding.

Step 13 Mix resin and dye without thickener to paint over the bottom layer of the patch
This mixture can be applied with a small paintbrush or cotton swab (if the patch is small). Apply it as evenly as possible, let it harden and rub with a very fine emery cloth ("zero").

Step 14. To restore and even out the gloss of the surface, polish the patch area with the polishing paste from the kit

Step 15. Wipe down your work surface and admire the work done
Advice
- Before adding the hardener, place a dot of the colored resin on the bath surface to compare the shade of the color. Correct the shade if necessary. Note that the resin will be slightly lighter after hardening! When you achieve the desired shade, immediately wipe off the resin by dampening a rag with acetone.
- Use special filling foam to repair large holes in the bottom of the tub or cabin. It will act as an additional foundation, avoiding further cracking of the bottom. Proceed according to the instructions on the package, then trim and sand the foam that has come to the surface.
- To repair large cracks or holes, you will need to reinforce the patch with fiberglass mesh or cloth, which are usually included in the kit. This complicates the repair procedure somewhat, and it may be worth asking someone who has already done this for help in this matter.
- A sander may be needed to repair serious damage.
- Polyester resin is temperature sensitive, so heating it with a hair dryer or a high power lamp will speed up the curing of the resin. Conversely, if you need more time to work with plastic resin, refrigerate it before mixing to extend its "working mode".
- Use a disposable container and mixing tool whenever possible. It is possible to remove polyester resin only with a strong solvent, such as acetone, and then immediately after application - later it is almost unrealistic.
- A drill with a polishing head will save you a lot of time and effort in the final stage of work.
Warnings
- Do not use foam cups or mixing containers. Solvent will melt them and spill the mixture onto the floor or your plumbing.
- Use rubber gloves (usually included) when handling solvents and mixtures.
- Acetone and most other solvents are flammable, so make sure there are no sources of fire, strong heat or sparks in the vicinity of the repair area.
- Protect skin and respiratory organs (with a respirator or gas mask) and provide good ventilation in the work area.
You will need
- Repair kit for acrylic (fiberglass) bathtubs
- Solvent or acetone
- Rubber gloves