Industrial designer Eric Strebel is at it again – this time with a how-to guide on making reusable mold boxes for casting silicone or urethane parts.

YouTube video

Eric has already skipped the boring part and cut the pieces out, so it’s just a matter of predrilling the sides to prevent the wood from splitting. He overlaps the pieces in such a way that each piece gets three screws and three screws screwed into them. This makes the box easier to reassemble later. These particular boxes are made of AC grade plywood with a veneer finish on one side for better casts.

After sanding and assembling all the sides, he marks the bottom with a pencil border as a point of reference. To connect this final piece, Eric drills an ungodly number of screws into the underside of the mold box, using the pencil border as a guide. While you could get away with using fewer screws, Eric states it’s better to be safe than sorry; at least you’ll be sure the box won’t leak or suddenly break down!

He also applies a generous helping of paste wax on the insides to further prevent leaks and keep the wood from absorbing the silicone.

Lastly (and this will delight those with a severe obsessive-compulsive disorder), Eric marks every side and part to make reassembling the box a lot easier. He even adds the box’s dimensions in centimeters AND inches on the underside.

As always, you can find more of Eric Strebel’s helpful design and production videos over on his YouTube channel.



Carlos wrestles gators, and by gators, we mean words. He also loves good design, good books, and good coffee.