How to tackle Soap Scum
Use an Acid
To remove soap scum that is not too bad, really hot water & a good scrub should do the trick. However, there are times we need to call on some cleaning products to help us out. In this case, you simply need to use something acidic like Vinegar or Citric Acid.
The one you find in the food isle next to the Balsamic & not the 'cleaning vinegar' which is not actually edible - because it's made from petroleum products! There is no need to dilute Vinegar for sprays or any solutions, it already has water in it.
1 teaspoon of Citric Acid to 1 litre of water will make a solution with the same pH as Vinegar (around 2-2.5)
Watch out for porous surfaces like stone as it can stain & etch. Do a small test patch in inconspicuous area, if safe go nuts! If not, then you need to turn to a supercharged cleaning paste.
SPRAY & WIPE
Use either Vinegar or Citric Acid solution in a spray bottle & spray the soap scummed surface.
MAKE & GEL
Blend 1/2-1 teaspoons of Xanthan Gum to 500ml of Vinegar/Citric Acid Solution. This will thicken it up to a gel that is perfect for certain cleaning jobs.
What's the science?
It's all about pH. The pH scale measures if something is acidic (an acid) or alkali (a base or basic).
My nature most cleaning products are alkali or basic like laundry powders, dishwashing detergent, mutlipurpose sprays & SOAP SCUM. Then you you have acidic cleaning products like fabric softeners, rinse aid, toilet & window cleaners. Do you notice anything there?
When you mix an acid with a base you are normally neautralising the effects. This is why you don't mix Vinegar with Bicarb unless you're doing a science experiment.