Posted on January 17, 2015
During the last couple months, I have been working on a large salad bowl mold for subsequent resin casting. I finally got to pour a test piece two days ago. After 40 hours since the initial pour, I have removed the top of the mold.
The resin datasheet says 72 hours to reach handleable hardness, so I've put the mold into full sun to speed up the cure a bit. The bowl at this stage it is still too floppy to remove and a few hours in the sun followed by a cool-off period should see a dramatic improvement in hardness.
This is one of several molds I've made recently that are all fibreglass ... i.e., no silicone. The bowl form has no undercuts and I will be post-finishing the product, so there is little advantage in using silicone ... and it's less work and less cost also. It does present a few extra challenges with mold release though ... hence my desire to get a test piece out of it and then do any necessary mold tweaking.
This is quite a big resin pour ... at approximately 1.25 L so temperature generation during the cure cycle is an issue to be considered. For this reason I am trialling a super-slow epoxy resin which so far is proving to generate a very low slow exotherm ... providing much reassurance for my desire to create larger objects.