How to Clean a Fiberglass Tub or Shower Without Scratching It
A fiberglass tub or one-piece shower surround has a thin, glossy gelcoat over a fiberglass shell. That gelcoat is what makes it easy to clean when it is new and what makes it a problem when it is not: it is softer than porcelain or tile, so the scouring powders and green pads that work on a ceramic tub leave a fiberglass one dull and scratched, and once the gloss is gone it stains faster than ever. The right approach is a mild abrasive that is gentler than the gelcoat but harder than the mineral and soap scum on top of it.
Is it fiberglass or acrylic?
Both are cleaned the same way and both need the same care. If the tub sounds hollow when you tap it and flexes slightly underfoot, it is one of the two. If it is heavy, cold to the touch and rings when tapped, it is enameled steel or cast iron, which is tougher and can take more scrubbing.
What you need
- A-MAZ Water Stain Remover. It contains no gritty pumice or chlorides, which is why it is safe on gelcoat where scouring powders are not.
- An A-MAZ Scrubber Pad, the gentlest of the two pads, designed for delicate surfaces
- A spray bottle of water and a soft cloth
- Ultra Gloss Sealant for the finish
Step by step
- Test first, always. On an older tub, pick a spot low on the wall or behind the drain and try the paste with light pressure. Some tubs that have been scrubbed with harsh products for years have almost no gelcoat left, and those are past the point of cleaning. If the test spot cleans up and stays glossy, carry on.
- Light pressure, wet paste. Dampen the pad, apply a little paste, and work in circles with the weight of your hand only. Mist to keep it wet. The soap scum and mineral film will lift and the original gloss will show through. Let the paste do the work; more pressure does not help and can dull the surface.
- Corners and the floor. The tub floor and the corners of a surround collect the most build-up. Take your time there, rinsing to check progress. Textured non-slip floors clean best with a soft brush and paste.
- Rinse thoroughly and dry.
- Seal the walls, not the floor. Rub a thin coat of Ultra Gloss Sealant over the walls and the outside of the tub. It restores the slick feel of new gelcoat and keeps soap scum from bonding. Do not seal the tub floor or a shower floor; the sealant makes them slippery.
Keeping it that way
Fiberglass stays clean with a rinse and a squeegee after use and a light wipe with the paste every month or two. Reseal the walls when water stops beading, about every six months. Skip abrasive powders, magic erasers and anything with bleach, all of which take gelcoat with them. The Shower Restoration Kit covers a full surround with product to spare.