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

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

  1. I have travertine tiles on the bathroom and shower floor so need to be careful with products. (Not my choice, btw). Definitely no vinegar I’m told. Would Bam Easy Off be ok, because some is bound to get on the travertine.
    Thanks for the great advice.

    • No reason you can’t use vinegar. It’s weaker than all the acids used in bathroom cleaners. BAM would also be ok

  2. I just bought a place which had been rented prior to purchase, and found this exact problem with the glass shower screens. Then I tried a WD40 equivalent – Selley’s RP7. It removes the white “frosting” effect of the etching. The etching effect is still visible, but it is more of a “clear cut glass” look- which is a lot less noticeable. well worth it as a short term fix. You don’t need to rub hard either and the result is pretty much immediate. Just leave it long enough to dry.WDE40 products are water-repellent, so it’s a useful shower cleaner already.

    • It hasn’t removed the frosting – it’s just filled in the valleys. But it’s not a bad idea. The other thing that could work is a silicone-based automotive polish. Or Mr Sheen. But be careful you don’t get the silicone polish on the floor – it’s very slippery

      • Ok so I have a completely clean glass screen when wet and feels super clean to the touch. However when it dries you can see the white water marks that seem cloudy. I have tried every possible suggestion but it seems I have this shower cancer as they call it. How can I make it not so visible. Do I use the WD40 spray on them leave??

        • If you have tried a good quality bathroom cleaner like Ajax Spray & Wipe Bathroom, then it has been etched. The term “glass cancer” was invented by Shannon Lush because she doesn’t know anything about the chemistry of glass. What has happened is that the glass has been etched by the alkaline soap scum, as glass is prone to etching by alkaline materials. As far as covering up the etch mark goes, I’d try Mr Sheen.

  3. I own a cleaning business and it baffles me the amount of time I see this issue and sometimes I have to inform them that this is never coming off. It pays to clean your shower and blinds regularly and floors!!!!! These are the main areas that need attention on a regular basis. You don’t realise how much grease can build up on blinds and how much damage your shower can obtain from saying ” I will do it next week
    ” because let’s be realistic, if your are time poor for cleaning it will come back and bite you. Renters and owners need to be aware of it. Cleaning is a long term investment and a short term reward

  4. I tried the Shannon Lush way. White Vinegar. Followed by wiping with Sweet Almond Oil. All it did was make it worse. It Smudged the Scum now my Shower Doors are Worse.

    • I’m not surprised. Acetic acid (vinegar) is far too weak to use on soap scum – the best stuff is sulphamic acid (BAM Easy Off). And it beats me why anyone would recommend almond oil for shower screens.

  5. I have found my answer for the shower screen problem. Use liquid soap only in the shower. (Not my brilliance btw). It works really well!! The claim is that hard soap contains fat which causes scum.
    Some general washing down still required of course for any mould buildup but no scrubbing, and now have clear screens. Whoopee!

  6. Does this mean that I should probably stop using the sodium hydroxide glycerol byproduct (that I use for cleaning just about everything) on my glass shower screen, mirrors and windows? It would be a shame, as it works a treat!


    • You make biodiesel do you? Yep that stuff sure does work a treat. I should post my own biodiesel methods up some day

      • No, I don’t make it – I tend to be absent-minded, and I don’t trust myself with the chemicals! I get it from people who do make it.

        So should I keep the glycerol away? I think my screen has etching, but not sure if it was there before I started using it to clean with, or if it’s happened since then.

  7. I agree. No amount of vinegar or bicarb soda will ever remove the soap and scum build up on glass. I find cleaners like Jif, a scratchy pad and a lot of elbow grease the best, but if the glass has been etched it will never be clear again. I clean rental homes for a living and see so much filth it’s unbelievable that people can let their showers (and the rest of the house) get so bad.

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