At work, they've been draught-proofing the old windows. It seem that this has involved squirting a big
bead of silicone along each mating surface, then closing the window until it goes off. Good (if
temporary-feeling) idea for some locations as it moulds to the right shape. Once cured, the silicone stays
on the one face.

They didn't do my area, so no chance to find out how it was done, but they must have used some release
agent on the 'uncoated' face for this to work.

Any idea what they might have used as a release agent?