I should have known I was in trouble when the Tamiya cement so reluctantly entered the syringe. But, my trusty MEK Pak has finally breathed out the last of whatever makes it work, and so, I was stuck (so to speak).
So I went ahead and made that test mould with Tamiya Cement. Plainly this stuff does not work the way I think it should. When I fed it into the joints, it stuck stubbornly outside, rather than racing between parts to melt them together. I’m sure it’s an excellent product, just incompatible with the way I work.
The result is that the silicone snuck underneath most of the parts, leaving a ragged edge of rubber where it got trapped when I pulled the mould off the master.
Lesson learned. Next time I will try Tamiya Extra Thin and make sure to go all the way around the masters. On a positive note, I don’t see any bubbles in the mould. So the vacuum chamber appears to do its job.