: The blemish didn't come from the water on the epoxy. By the time I sanded it
: was pretty hard and not tacky at all. The white blemish came from sanding
: a hardened puddle of epoxy. I used a slightly damp rag to wipe the dust
: off from sanding before I put the glass on. I thought the blemish would go
: away when I put fresh epoxy on it but it didn't

Rubbing alcohol would probably have worked in this situation -- it sounds like you didn't get all of the dust off/out of the epoxy. I've used rubbing alcohol to flush dust off/out of sanded epoxy with good results... the operative word here is "flush" -- not dabbing with a rag (potentially just moving the dust, not removing it), but using the alcohol to rinse the area....and obviously waiting until it has entirely evaporated before proceeding.

: I'm facing the same problem again. Its been more the 24 hours since I put the
: glass on and I guess I'll have to sand before I start fill coating. At
: what point does the chemical bond go away and mechanical bond needed?

You've got about a 72 hour window, according to the System 3 book. (Presuming that the temperatures are within the 'normal' range for the cure time for your hardener) -- if you need to buy a little more time, turn the heat down!!)...I'd imagine that the time frame holds true for other brands of epoxy as well. You really want to avoid sanding the glass prior to applying fill coats. If you cut into the weave of the glass you'll weaken it.

It doesn't take long to do a fill coat. I figure on about a half-hour, start to finish. (Based on having built an Arctic Tern & two Coho's.)

Julie Kanarr