mx wrote:
Will all epoxies bond to one another? I have some West GFlex, which I
want to use thickened to fill a gap between two loosely-fit fiberglass
parts, and some System Three laminating resin (Clear Coat, I think, I
don't have it with me right now) that I then want to use with glass
tape to reinforce over the surface of the joint. Will the epoxies
bond well to each other, if the glass is applied within a few days of
the first resin?

Also, is colloidal silica and microballons the same? I have an old
bag of house-brand microballons from Fiberlay, and colloidal silica is
recommended as a thickener. I feel like I used to know the answer to
this...but, apparently, I'm an idiot!

Thanks,
Mike
You have gotten good answers, but one thing was not covered.
Most Epoxies blush to some extent.
If you don't sand both parts, then at least wash them well. You can
actually use a detergent and clean water rinse.
Matt Colie