Silicone-bearing material transferred to a glass or coating surface from sealants, lubricants, gaskets, handling, or adjacent work.
GlassRenu · Educational illustration
Meaning and boundaries
Silicone contamination can be nearly invisible when dry and should not be confused with structural glazing sealant that remains where designed.
Why it matters in glass restoration
It can cause persistent smears or abnormal water beading, attract soil, mask self-cleaning behavior, and resist ordinary cleaning.