Polytek 74-45 Liquid Polyurethane Rubber (16lb Kit)

This stuff is amazing. If you need to create an almost indestructible 'rubber' mold you're looking at the right stuff. I've cast almost 20 bricks in the 2 molds I made from this stuff and after I clean them, they look like the day I created them. I went to my local Ace Hardware store bought one of those paint measuring buckets to mix A & B. Cleanup needs to happen quickly. The mixture has the consistency of something between maple syrup & honey. You can reseal the buckets at least once. Removing the brick I used to make the mold was challenging, I suspect I used the wrong release agent. Removing the bricks I made with the molds was not nearly as challenging. I sent Polytek an email on release agents and received an accurate and professional response within 24 hours.