Silicone putty mold making

Lego pieces

How to use two part silicone putty to make a mold

Don’t tell my kids, but their Legos have once again made it into my latest resin experiment.

To be quite honest, I haven’t spent much time with two part silicone putty for mold making.  When I first learned mold making, I started with pourable silicone and have pretty much stuck with it ever since.  When one of the companies I work with gave me a free sample of silicone putty to try, I couldn’t pass on the chance to see how I would use it.

Enter the need for children’s toys once again.

mixing silicone putty

To mix the putty, you need to start with equal parts.  I didn’t weigh or measure the putty; I simply ‘eyeballed’ it.

 

 

 

 

 

mixing silicone putty

The working time with this product is short, (less than 3 minutes!) so you will need to work fast.  Mix the two parts together until it is completely blended.  I felt it warm up slightly in my hands.

 

 

 

pushing model into mixed silicone putty

Once it’s mixed, push and form it around your model.  This can be tricky.  You want push the model in the wad of putty and make sure it comes up the sides as well.  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.

 

 

 

 

flatten bottom of mold putty before allowing to cure

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.

 

 

 

 

 

Lego models in silicone putty molds

Allow the putty to cure.

 

 

 

 

 

 

 

 

demolding Lego from mold putty

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.)

 

 

 

 

 

 

 

Broken crayons for remelting in silicone mold

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 pile of broken crayons could get put to good use!  This mold putty is heat safe up to 400 F (along with being food safe), so I decided to make Lego crayons.

 

 

melted crayons in silicone mold

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.)

 

 

 

demolding Lego crayon

The crayons were cool enough to demold in about 20 minutes.

 

 

 

 

 

 

Lego crayons

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.

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So what do you think?

3 Comments

Katherine Swift

@Susan, I don’t think the amount of putty was the problem. I think it had more to do with the wax breaking at a thin point (between the claw hand and the arm). I would be game to try the Alumilite Amazing mold putty though to see if that makes a difference. Thanks for the suggestion!

Reply
Susan

You didn’t use enough putty. You have to use a lot if you’re going to melt crayons or soap in the molds because you need a deep enough cavity for the end product to be sturdy enough and also the corners of the molds can rip if too little putty is used. I prefer Amazing Mold Putty to this one. I did a whole Lego themed birthday party for my son and make many of these molds for melted chocolates and crayons.

Reply
RonnyJ

Thank you for sending this. Now I understand what the other was referring to.

Reply

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