Anne
It may be a screw inside the extrusion rusting or metal swaf
rusting. The acid in the silcone attacks screw head causing yellow stains (some times ) not much you can do, clean with cif.
david 30yrs a d/glazer
October 2006
Ann. There is no yellow substance added to window extrusion during the manufacturing process. An outside possibility is that some joker stuffed a sweet into it before it was 'V' cut, bent and welded.. More worryingly though is how it is getting out.
Kev@K.L.Plastics
Kev
October 2006
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