Making silicone molds seems easy, but there are a lot of missteps to be made along the way that can mean the difference between a great, reusable mold, and one that’s a sad waste of silicone. If you’re helpless to know the difference, then check out [Eric Strebel]’s 9-minute masterclass teaser video on making a two-part mold for resin casting, which is also embedded below.
Even if you already know how to do this, there’s probably a good tip in here somewhere. One of them being that you should always pour your silicone from one place and let it coat the piece being copied. Otherwise, there might be lines on the mold. Another tip is for DIY mold release made from petroleum jelly thinned with naphtha.
Our favorite tip has to do with the way [Eric] makes this a reusable two-part mold, which is more akin to injection molding. To pour silicone for the second part and get it to separately nicely, [Eric] uses sprues made out of resin rods that were cast inside of drinking straw molds. These he chamfers against a belt sander to minimize the contact with the cast part, which makes them a snap to break off. [Eric] says this is just the beginning, and there are more videos to come that will break down the steps.