On Sun, 30 Jun 2019 05:53:03 +0100, Stephen wrote:

I used to use Mr Muscle cans of caustic soda to clean them and that
worked but I find the cheap tins of caustic soda do not, so perhaps they
use a less concentrated spray?

Modern domestic chemical cleaning products are hopeless. For glassware,
you will find chromic acid or trisodium phosphate with a bit of Vim
thrown in for good measure always does the trick. That's what we used
back in the 60s and I've never found owt better.



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