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