Originally written April 2015. Updated April 2020.
Don’t tell my kids, but their Legos have once again made it into my latest resin project. Molding and pouring silicone to make a resin mold isn’t always the easiest thing to do. For beginners, I recommend two-part silicone mold-making putty as there isn’t need for a mold box and it cures much quicker than poured silicone. Here’s how to use two-part silicone putty to make a mold.
To mix the putty, you need to start with equal parts. You don’t need to weigh it — simply eyeballing it is enough.
Blend the two parts together until it is uniformly blended. The working time with molding putty is short, so you will need to work fast. You will feel it warm up slightly in your hands.
Once it’s mixed, push and form it around your model. This part of using silicone molding putty can be tricky. You want to push the model in the wad of putty and make sure it comes up the sides as well, but don’t try to flatten the putty into the model. You may not get all the detail from the original model. Just think of it like this — put the model into the putty, not the other way around.
Before you let it cure, be sure to flatten out the bottom of the mold. Otherwise, you may not have a level surface for casting.
Allow the putty to cure.
This silicone putty cured in 30 minutes! Once done, lift out your model. (My kids had busted me at this point and were quite relieved to see the Legos were unharmed.)
So here’s where it gets a little crazy — what could I do with this mold that I hadn’t done yet? I decided that a pile of broken crayons could get put to good use! This mold putty is heat safe in a warm oven (along with being food safe), so I decided to make Lego crayons.
After 10 minutes in a warm oven, the crayons had melted into the mold. Note to self though, place the molds and crayons on aluminum foil next time. They dripped over the side and made a mess in the bottom of my toaster oven. (Although kids were highly entertained by the wax burnout lesson and small fire in the toaster — but I digress.)
The crayons were cool enough to demold in about 20 minutes.
Here are my finished Legos. The brick Lego came out pretty nice. You can even see the brand imprint on the raised pegs. The minifigure didn’t do so well. The hands were in the mold rather tightly. It snapped in half as I was removing it. I think resin would do better and not break during demolding.
So what do you think?
Unpublished Blog Posts of Resin Obsession, LLC © 2015 Resin Obsession, LLC