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.