"Peter Charles Fagg" wrote in message
oups.com...
When I posted this message I had not expected someone to interpret my
using a Brillo pad or the scalpel all over the glass, it was tested in
a very small section at the bottom where any scratching would go
un-noticed.

The harshest treatment has been the Lime-Lite but it too is totally
ineffective.

I shall probably try this Cillit Bang that other refer to as a last
resort.
Had a similar problem, despite a water softener being fitted to the house,
scale on shower glass appearing over a year or two that would not shift
easily using standard cleaning/descaling products. A mate tested the "scale"
it at his work and it was calcium sulphate not calcium carbonate which is
normal scale. Calcium sulphate is not attacked by standard cleaners or even
brick cleaning acid.

So not too sure what the cure is.