I'm probably late with this reply, but one of the reasons to thicken epoxy is to keep it from getting squeezed out of the joint that you are gluing.
If the joint is very precisely fitted, and you clamp the parts together while the adhesive is curing, there is a danger of "starving" the joint - that is, squeezing out so much of the adhesive that not enough is left in the joint to do its' job.
Thickening the epoxy can't totally prevent this, but it helps.
On the other hand, let's say your joint is not perfect - it has some pretty big gaps in it. In that case, unthickened epoxy might just pour out of the joint, leaving gaps. Thickened epoxy would stay in the joint, filling gaps.
I suspect that thickening epoxy TOO much would probably interfere with adhesion, but I don't have facts to back that up... maybe one of the other guys will comment.
I thicken epoxy a lot for making fillets, a lot less for use as an adhesive, and not at all for glass work.
George
If the joint is very precisely fitted, and you clamp the parts together while the adhesive is curing, there is a danger of "starving" the joint - that is, squeezing out so much of the adhesive that not enough is left in the joint to do its' job.
Thickening the epoxy can't totally prevent this, but it helps.
On the other hand, let's say your joint is not perfect - it has some pretty big gaps in it. In that case, unthickened epoxy might just pour out of the joint, leaving gaps. Thickened epoxy would stay in the joint, filling gaps.
I suspect that thickening epoxy TOO much would probably interfere with adhesion, but I don't have facts to back that up... maybe one of the other guys will comment.
I thicken epoxy a lot for making fillets, a lot less for use as an adhesive, and not at all for glass work.
George