Hi,just a question on cleaning this type of glass without doing damage,funnily the base has quite easily removed dirt,further up there is some light scale of some sort, at the top in the folds some thicker deposits,witch seems a bit odd to me?,that I have been able to remove a few bits with light rubbing with my thumb nail,just as another bit of info the base ,in the thickest parts,there is a distinct green end of the yellow spectrum colour when viewed from above.