Introduction: Zero Mess Hot Glue Molds? It! Could! Work!

About: Wow! Such science! Very lab! So research! Many awesome!

So, I wanted to make some pendants for my fencing group. I already worked with hot glue as a casting material (see ) but I always thought there could be an easier method for using it.

The advantages is that the casting process is very quick, as you don't have to wait hours for the resin to harden, and the resulting replica is flexible, and can be safely used even with sword going around it without risking of breaking it.

But the usual method of casting hot glue was a really messy. Usually one would heat up some hot glue over a stove, trying to balance the correct temperature (too low and will not melt, too high and will burn), waiting for all of it to melt, and then very slowly (since hot glue has a very high viscosity) pour it in the mold, trying to not breath in the toxic smoke...

In the end, I devised a method for making quick, easy, cheap and durable molds using hot glue. Are you ready?

Step 1: You'll Need

The main things you'll need are:

  • hot glue sticks (wouldn't you say? xD)
  • a small electric oven, with the heating element on top
  • acrylic color (optional)
  • mold release spray

For the mould you'll need:

  • pure silicone
  • flour
  • mineral spirit

Step 2: Making the Mold

With my 3D printer I made the master, then I prepared the material for the mould with the pure silicone - flour - mineral spirit recipe (you can found out more here, in THE master instructable :P )

I found in a kitchen store these circular shapes, very handy for making moulds! Just spread the silicone out evenly, press down the original, and wait for it to dry.


  • I placed a small rock as weight on the master for ensuring good quality on the mould.
  • I also tried to press the silicone on the original, but didn't work so well.

Step 3: Prepare the Glue Bits

One important part is that all the hot glue is completely painted, so even if the replicas are scratched, you will not see a different color underneath.

This step is optional (you can always paint the glue later), but I found easier to work with painted hot glue in the first place.

So I bought in a kitchen store this silicone piece, originally for cooking eggs I thinks. Simply put the acrylic paint and the hot glue, heat it for several minutes (until it's completely melted).

Then put it in a bowl with water, wait for it to cool down, separate it from the silicone (it should separate very easily) and cut it to pieces.


  • Stay away from the oven while the hot glue is melting, and ALWAYS do this outside your home!
  • For faster melting you can keep the oven's door closed.

Step 4: Cooking Time!

Now it's time to "bake"!

ALWAYS use a mould release spray for keeping the mould in shape.

Put some bits of coloured hot glue on the mould, approximately the mass of the master plus a little more. Turn on the electric oven, and the glue on the top will melt, slowly falling down and filling each detail!

The time needed depends on the oven and the mould, for these little pieces 10 minutes were enough. I left the door of the oven open, since I wanted a slow heating (too fast and the hot glue will start to "boil" and form bubbles).

I was able to make 3 pieces in half an hour: put the hot glue pieces, set the timer, walk away (in this way even if the glue fumes you are not affected), come back, put the mould in cold water, wait 10 seconds, separate the replica and start again.


  • Keep the oven's door open - slower and steady heating will give the best results.

  • For the hot glue in excess, simply cut it and use it for the next round! If somehow a replica doesn't come out well, simply cut to pieces and try again!
  • It is very important to always use bits of hot glue, and not a complete piece. This way it will melt quicker, and fall down filling each detail.
  • Again, stay away from the oven while it's working, and ALWAYS do this outside your home!

Step 5: It! Could! Work!

Here we are!

  • Very easy
  • Really cheap (hot glue has a really low cost compared to other casting materials)
  • Insanely quick (10 minutes for a completely cured replica!)
  • Zero mess (no intoxication, no risk of burning yourself with melted glue)

... what more could you possibly want? xD