Silicone is truly evil.

[ebb]

C'amos, G'day,
Think to add, thanks to your banner headline/thread, something you know, but others might not.
That is,
Do not use any solvent (or heat) in the attempt to prep the surface of the evil silicone violated surface. Solvents are drivers, they will end up pushing the oily residue deeper into the porus gelcoat. Mechanical scraping, hand scuffing with nylon pad without heat buildup is the only way. And the caveat to this is the grit of sanding sheets can make deeper grooves into which the silicone oil is forced. What they say.

The oily stain produced by silicone is a general observation by workers. Haven't seen any micro photos of this phenomenon. Ditto sanding surface grooves with silicone deposits. Sometimes this kind of 'knowledge' gets passed from one author to another like rumors. Like it sounds right. It might not be as bad as you've been led to think. And you may have done some of this we're not supposed to do. I have. Therefor test the de-evil-siliconed surface with a daub of good quality 2-part epoxy. Let it set. See if you can lift it off with a metal spatula.

If you can, then more scraping (shaving) is necessary. You find hand scrapers with carbide blades, including shaped ones, in independant hardware stores. BACHO has nice ones for detail, and just got a two inch wide one from Rockler but haven't tried it yet on glass, which is the test.

But if you don't want to mess with the gelcoat. it is possible to have a solution with a mental shift! Instead of attempting to create a surface that adhesive will stick to........ just consider it a bearing surface requiring a gasket. The wood on an A/C shouldn't be glued on, metal fittings neither. They are bedded with the main purpose to keep water out of the thru fastenings. Deadlights would be better served if they compressed a gasket. So, in theory, no prep is necessary at all!

White vinegar for two-part epoxy clean up is a green alternative becoming popular. Perhaps it might be useful as a degreaser/cleaner for rebedding. It is easier to use than Simple Green detergent in the work place.