I doubt the mold is penetrating the substrate. I suspect the mold is secreting the coloring matter, which is being absorbed into the silicone. Among polymers, silicone ranks highly in permeability.
Same here ! I tried coating it with toothpaste in the hope that the flouride would kill the fungus - but it either washed away or dried out and the black colour of the mould stayed ! Perhaps its specific to UK brands. My sealant was white.
Try improving your ventilation or removing excess moisture...mold loves dark, damp areas.
Silicone sealant, by itself, will not support the growth of mold or mildew.
The reason mold grows on sealant used in the shower is the soap film that builds up on the surface of the sealant - which does support mold.
The solution is to use silicone bath tub caulk. This is one case where the product is not simply a marketing driven re-label of standard silicone. Bath tub caulk contains a mildew suppressant that permeates the overlaying soap film and prevents the mold. It really works!
RT
Try using a decent caulking compound made for sealing tubs instead of silicone and sealing with the proper sealant after it dries several weeks.
Gordon
Thanks, I have seen tubes of "caulk" - I'll check these out. Richard
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