How do I bring the shine back to a dull or stained acrylic bath?

Acrylic is a soft, glossy plastic. Its shine comes entirely from the surface being smooth, and every scouring pad, every cream cleaner with grit in it and every dry wipe over gritty limescale takes a fraction of that smoothness away. After a few years the surface is a matt web of micro-scratches that holds soap film, looks yellow-grey under the light and gets harder to clean each time — which drives people to scrub harder, which makes it worse. The cure is the same as for a car's paintwork: cut and polish.

What you'll need

• Fine automotive polishing or cutting compound
• Acrylic or plastic polish for the final stage
• Several soft microfibre cloths
• Wet-and-dry abrasive paper, 1500 and 2000 grit, for isolated deep marks
• A random orbital polisher with a soft foam pad, for a large bath

Step by step

1. Establish that it is dullness and not staining.Wet a patch and look at it while it is wet. If the wet patch looks glossy and normal-coloured and goes dull again as it dries, the surface is scratched and this guide applies. If it stays discoloured when wet, it is a stain and needs treating as one.
2. Clean and degrease first.Wash the whole bath with washing-up liquid and warm water, rinse and dry. Polishing over soap film and body oil just moves them around. Do not use any abrasive cleaner at this stage.
3. Test in one small area.Pick a spot near the tap end or under where the panel line runs. Work the compound in a small circle with a folded microfibre for a minute, then wipe clean and look at it. You want to see gloss returning, not a hazier patch. If it hazes, your compound is too coarse.
4. Work the whole bath in sections.Do about a quarter of a square metre at a time, with firm circular pressure, then buff off with a clean cloth before it dries hard. Overlap sections. By hand this is genuinely hard work on a full-size bath, which is why a soft foam pad on a slow-speed polisher is worth borrowing.
5. Deal with isolated deeper scratches separately.Wet-sand only the scratch itself with 1500 grit used wet, in one direction, until the scratch has gone, then 2000 grit across the first direction, then compound the sanded patch back to gloss and blend outwards. Do not wet-sand the whole bath.
6. Finish with a plastic polish.Compound leaves a fine finish, not a full gloss. A dedicated acrylic or plastic polish over the top brings the depth back and leaves a slick surface that sheds soap film.
7. Rinse everything off thoroughly before use.Compound residue is slippery and sits in the texture at the base. Wash the bath out with detergent and rinse well before anyone gets in it.
8. Change what you clean it with.From now on: liquid bathroom cleaner or washing-up liquid, soft cloth, and dry it after use. No cream cleaners, no scouring pads, no magic erasers — melamine foam is a very fine abrasive and it dulls acrylic.

Tips

• A yellowish tinge in an old acrylic bath is usually soap and body oil in the scratch texture rather than the plastic itself having aged. It comes off with the compound.
• Do the base last and check it afterwards — a polished bath base is slippery until it has been washed out properly, and some texture at the base is deliberate.
• If you are already polishing, do the acrylic bath panel at the same time. It is the same material and it usually looks worse than the bath.

Common mistakes

• Reaching for a stronger cleaner — Dullness is a physical surface, not a chemical one. Stronger and grittier cleaners deepen the problem they appear to be solving.
• Using a coarse rubbing compound — Acrylic is far softer than car paint. A coarse cutting compound puts in a haze that then takes several stages to remove.
• Wet-sanding an area you have not tested — It is easy to sand a hollow into acrylic that is impossible to blend out.
• Using acetone, nail varnish remover or a solvent cleaner — Solvents craze acrylic. The crazing is permanent and it is much worse than the dullness.

Keeping on top of it

• Rinse and wipe the bath dry after use (each use)
• Full clean with a non-abrasive bathroom cleaner (weekly)
• Plastic polish over the whole bath (every 6-12 months)