A couple of months ago, my wife gave me a Proxxon hot wire table as an
anniversary gift. Right away I spent a couple of lunch breaks cutting scrap XPS
foam into bricks - enough to fill a large yoghurt tub. These I distressed by
tossing them with gravel from the garden and I set them aside. This weekend I
laid them out into two 3" square patterns, with the intention of casting tiles.
I sealed the tiles with a couple of layers of Modpodge mixed with baking soda.
Any gaps or cracks would be sure to fill with silicone and rip during mold
making, so it's important to seal as many as possible. I was worried, though,
that I would fill in too much detail.
After sealing, I used more foam core to build up the sides into a box, which I
filled with silicone. After a few minutes in the vacuum chamber to draw out any
air bubbles, these sat overnight. Great success, the silicone found no errant
gaps! I was still worried about loss of detail, so I tried the first cast in
resin.
As I intend these molds to be cast in the open, and to capture any excess resin
I may have mixed during other projects, I tested without using the pressure pot.
While there are loads of tiny bubbles, overall I think the tiles turned out
pretty well.
A second attempt at casting under pressure failed, as adding air into the
pressure pot caused the resin to be blown out of the mold. I am going to have to
modify the pot to divert incoming air and avoid any disturbance in the surface
of the mold, any mold.