I’ve spoken before about using Legos for moldmaking, and the fact that I have been limited to small molds because modern Lego sets don’t actually have many of the traditional rectangular pieces. I thought I’d need to haunt the yard sales this summer to see if I could find some of the older sets, but it turns out you can buy Legos online in bulk.
Joan Berkwitz also gave me a wonderful tip that makes clean-up a lot easier. If you coat the inside of the Lego mold with a little vaseline, it will seal the brick lines so the rubber does not seep into the grooves. If the rubber really gets in between the bricks, they can be really difficult to pry apart without damaging the bricks, so I really recommend it!