Steam up the bathroom and look at your shower screen from the side. If the glass looks clear when it is wet and chalky once it dries, you are not fighting dirt — you are fighting limescale. That milky film is the calcium and magnesium left behind every time hard water dries on the surface.

The good news is that limescale is alkaline, so a mild acid dissolves it. Get the strength, the contact time and the tools right, and the glass comes back clear without scratches, cloudiness or chewed-up seals.

First, work out exactly what is on the glass

Run a fingertip over a dry patch. Soap scum feels slightly greasy or soft and will partly wipe away with washing-up liquid and warm water. Limescale feels dry, rough and faintly gritty, and it shrugs off anything alkaline. Most screens have a mix of both, which is why a general bathroom spray shifts the greasy layer and leaves the white one behind.

There is a third possibility: etched glass. If the screen stays milky even when it is soaking wet, or the surface feels pitted like fine sandpaper, minerals have permanently marked the glass. Acids will remove the deposit sitting on top, but they cannot polish out the etching underneath. In that case, live with it or price up a replacement panel — a glazier can advise on whether the glass is worth saving.

What to keep away from a shower screen

Half of the damage done to shower glass comes from the cleaning tools, not the stains. Before you start, put these aside:

• Steel wool, wire brushes and razor blades. They leave fine scratches that trap more scale and look worse than the original film.
• Cream cleansers, powdered abrasives and green scouring pads. Too coarse for glass, and they dull an easy-clean coating in seconds.
• Bleach alongside an acidic cleaner. The two react to release chlorine gas. Never combine them, and never mix cleaning products in general.
• Acid left sitting on seals and frames. Vinegar and citric acid will soften silicone and rubber over repeated exposure and can pit chrome, brass and aluminium. Keep the acid on the glass and rinse the rest afterwards.
• Oven cleaner, drain cleaner and toilet descaler. Far too aggressive for glass, coatings and seals.

Also check whether your screen has a factory easy-clean coating. If the manufacturer says no acids, use a dedicated coating-safe limescale product instead and follow the label exactly.

The white vinegar method

White vinegar is around 5 per cent acetic acid, which is enough for light to moderate scale. This is a wet job — dried-out acid leaves a residue and can mark the glass, so keep everything damp.

You will need: white vinegar, a spray bottle, several microfibre cloths, cling film, a plastic scraper, and a squeegee for finishing.

1. Open a window or run the extractor fan, and put on rubber gloves.
2. Test a small corner first, especially near the frame, and leave it for ten minutes to check for any reaction.
3. Soak a cloth in vinegar and press it flat against the glass, working in sections from the top down. Cover the cloth with cling film so it cannot dry out.
4. Leave it for 15 to 30 minutes. For heavier scale, leave it longer — but re-wet rather than letting it dry.
5. Lift the cloth away and rinse thoroughly with warm water. Wipe the seals and frame with plain water at the same time.
6. Dry with a clean microfibre cloth and finish with a squeegee.

If one pass only thins the film, repeat tomorrow rather than reaching for something stronger today. Scale comes off in layers.

Citric acid for scale that vinegar will not shift

Citric acid powder is stronger, cheaper per use and far less smelly. Dissolve a couple of tablespoons in a litre of warm water, spray or sponge it onto the glass, cover with cling film and leave for 20 to 30 minutes. Rinse well, then dry.

If you would rather buy a bottle

Look for a bathroom limescale remover based on citric or sulfamic acid, and check the label says it is suitable for glass and the fittings around it. Apply it to the glass only, respect the stated dwell time, and rinse the frame and seals afterwards. Proprietary acids are often strong enough that a five-minute dwell beats a long soak.

Two sensible cautions

Acids etch natural stone, so keep them off marble, limestone and travertine tiles and any stone tray. And if you are unsure how old, brittle or already damaged your seals are, a plumber or a glazier is the right person to ask before you start soaking the enclosure.

Scrubbing without scratching

Once the acid has done its work, most of the deposit lifts with a cloth. For stubborn rings, swap to a non-scratch nylon pad — the white ones sold for non-stick pans — or a plastic scraper held at a shallow angle. Work in small circles with light pressure, and keep the glass wet the whole time. A cloth wrapped over a washing-up sponge gives you a little more grip without grit.

Avoid melamine "magic" sponges on coated glass; they are mildly abrasive and will gradually dull the surface. And never scrub a dry screen, however tempting it is when you can see the marks clearly.

When the scale has been there for years

Thick, crusty rings usually need a week of short, repeated treatments rather than one marathon session. Two or three minutes of acid each day, rinsed and dried properly, will thin the deposit steadily. For a final push, make a paste from citric acid and a little water, spread it over the glass only, cover with cling film and leave it for a few hours.

A steam cleaner helps soften stubborn edges before you treat them. If nothing works and the surface stays cloudy when wet, the glass is etched and no amount of cleaning will restore it — at that point, replacing the panel is often the cheaper answer.

Keeping the glass clear from now on

The most effective thing you can do costs about twenty seconds. Keep a squeegee in the shower and pull it down the glass after every use, then leave the door open and the fan running so the enclosure dries instead of spotting.

Beyond that: switch from bar soap to a body wash if soap scum is a recurring problem, mist the screen with diluted vinegar once a week and rinse it off, and consider a shower filter or water softener if your water is very hard. Finally, if the screen has a coating, check what the maker recommends before applying anything acidic to it. Clear glass is far easier to maintain than it is to rescue.

Photo: Msobaidi / Pixabay