The Chemistry of Cleaning #3: How to Clean Shower Screens

Last Monday on 6PR a caller on 6PR asked Shannon Lush how to clean shower screens.

She advised against using commercial products and instead suggested vinegar.

Let’s have a look at it. Exactly what is the grime on shower screens?

There are essentially two components of shower scum – mineral deposits (usually calcium carbonate) and soap scum. Soap scum is either the calcium or magnesium salt of the soap molecule.

Either way, the deposits are alkaline.

So to get them off, you need an acid. It needs to be a strong enough acid to dissolve the alkaline salts, but not so strong that it’ll either etch the glass or attack the alloy trim in the shower.

As it happens, there is only one acid strong enough to etch glass – hydrofluoric acid – and it’s certainly not sold over the counter to the general public. Other strong acids – hydrochloric and sulphuric acids – are available over the counter, but they would attack the metal in the shower recess so we won’t use those.

Vinegar – or acetic acid – is not a bad option, but a better option is sulphamic acid (found in BAM and also a toilet cleaner that Bunnings sell). It’s a stronger acid, will get the alkaline salts off easier, but won’t damage the metalwork.

But whatever you use, you may find that it never comes quite clean, and appears to still have deposits on there.

This is caused by the soap scum etching the glass. Soap is make from caustic soda and fat, and so the salts of the soap are highly alkaline. And glass is much more prone to etching by caustic soda than any acid. Anyone that works in a lab knows that you don’t store solutions of caustic soda in glass.

So the highly caustic soap scum will etch the glass. So even after you clean it off, you can still see the etching behind that it has left. I suspect this is what Shannon Lush calls “glass cancer“: But unfortunately her advice to use Goanna Oil won’t make a scrap of difference

So the lesson is – don’t let highly caustic soap scum build up on your shower screen – keep it clean

2320cookie-checkThe Chemistry of Cleaning #3: How to Clean Shower Screens

44 thoughts on “The Chemistry of Cleaning #3: How to Clean Shower Screens

  1. Hey I see nobody mentioned Cutback car polish
    I have the same problem with the shower screens
    Just remembered I have 4 liters of the stuff under the house

  2. Tenant vacated after 5 years and not sure exactly whether the issue was water stains or etching, however I’ve spent a week scrubbing and trying many many different products and methods. What has been most helpful was the application of INOX-mx3 lubricant. Floor tiles covered, well-shaken, carefully sprayed on and then worked into the screen using a circular motion.
    INOX is an anti corrosion/anti-moisture penetrating oil. It doesn’t go gummy like some other products and although the screen has a slight haziness it’s clear, has substantially reduced the visibility of the marks and therefore very satisfactory. Will see how it performs with the next tenant.

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