How to Do Metal Casting with Plaster, Wax, ComposiMold, and Metal

Posted by ComposiMold on 30th Jan 2020

How to Do Metal Casting with Plaster, Wax, ComposiMold, and Metal

Here we show you how to make your own metal castings using the Lost Wax process. You can make shapes you make yourself into metals such as tin, aluminum, lead, silver, gold, and other metals.This is great for die casting, jewelry making, and many other applications where you want metal objects.


Before we begin, most importantly be careful and use good judgment, Melted metals are very hot and can severely burn you.

The equipment that you will need includes:

Your original shape, We are using a 3D printed eagle, but you can make your original or master object from other materials including, plastic, wood, clay, or polymer clay. You can learn more about what you can and can’t mold with ComposiMold or ImPRESSive Putty by getting your free ebook on the ComposiMold website.

You will need your mold making materials, ComposiMold or ImPRESSive Putty. We will first show you the ComposiMold, but at the end of this video we will also show you the ImPRESSive Putty. Both are reusable. The ComposiMold is a heat and pour and will pick up great details simply by pouring. For the ComposiMold, use either the ComposiMold-Original or the ComposiMold-Flex so you can bend the rubber mold around the wax without causing damage. Also, for the ComposiMold, you will need to chill your mold prior to pouring in the wax. You cannot use the ComposiMold for microcrystalline waxes because of the higher temperatures. Use ImPRESSive Putty instead.

The ImPRESSive Putty is a heat and press material that is extremely easy to make molds with, but is firmer, so you may need to make cuts in the mold to remove the wax without breaking it. However, if you use ComposiMold instead of the wax, you will not have any issues. We’ll show you that in another video, but trust us, it’s pretty cool. The ImPRESSive Putty can handle higher temperatures so you do not need to chill the mold first.

Other materials you will need to make your metal casting using the lost wax process is a wax. I like beeswax, but you can use microcrystalline waxes with the ImPRESSive Putty. You can experiment with other waxes as well.

A metal. We’re using tin. Higher temperature metals such as steel are likely out of the temperature range you can do in a DIY environment.

ComposiMold Plaster. ComposiMold plaster contains an additive to make good strong molds in and around ComposiMold.

Torch. If you have a high temperature oven that will work too.

Something to hold the melted metal in. I use a small crucible.

Pliers to hold the hot metal

Eye protection, hand protection, and body protection. Please be careful. This is dangerous if not done with care.

And some random containers and stir stick

Plus an oven, and a fire extinguisher for safety is also a good idea.

Do this in a well ventilated area. If in doubt, do not do it.

Okay, are you ready? Let’s make a metal casting!

So the general steps for metal casting using a lost wax molding process is here.

Make a ComposiMold mold of your object so you can make a wax casting so you can make a disposable plaster mold that can handle the heat of the metal.

It’s much easier than that sounded, so lets start. Melt the ComposiMold in the microwave for about 40 seconds for a small amount. Make your rubber mold by pouring ComposiMold around your object. To stop this eagle from floating I could hot glue it down, but instead I poured a little ComposiMold into the cup and let it solidify. Then I poured the rest of the ComposiMold over and around the object. The already cool ComposiMold holds the eagle in place. To cool this faster, I placed the mold in the freezer.

After solidified, in about 20 minutes, I pulled off the mold box container and pulled out the original. Many people like using Legos to make the mold boxes. In this case a cup worked fine.

The ComposiMold mold is ready to for the wax. I want the mold to be cold when I pour, so while the mold is still cold being in the freezer, I melted the beeswax and poured it into the mold. Let the beeswax cool so it is on the edge of solidifying again to reduce any possible melting to the ComposiMold. The wax will cool from the outside in, so it will chill in the correct shape.

You can also use ComposiMold to pour into the ComposiMold mold. I will show you that process in a different video. Subscribe to our channel to be there when that video is ready.

After this cooled in about 15 minutes, I removed the wax eagle from the ComposiMold.

If I was making beeswax candles, this would be the finished product. And it is very nice.

Now we make the disposable ComposiMold plaster mold using the wax Mix the ComposiMold plaster with water at about 2.5 parts by weight or volume plaster to 1 part water. I typically just eyeball it and make it as thick as possible while still being pourable.. Place the wax eagle into another mold box, or cup.

Pour the plaster around the wax figure and let solidify for at least an hour. Two hours or even overnight is better.

Cut away the mold box to Remove the plaster mold from the cup and Now comes the lost wax process.

The eagle wasn’t quite on the bottom of the mold box so I chipped away a little of the plaster so I had a hole to pour out the wax and pour in the metal.

Flip the mold upside down and melt out the wax. I use a few stones to keep the mold up in the air so the wax can come out. You can reuse the wax as well. I melted out the wax at 350 F in an oven for about 20 minutes. Don’t let the wax overheat, it can catch on fire.

After the wax is removed, continue to warm the plaster to remove more water. You also want the mold warm when you pour in the metal so there is less temperature difference between the plaster mold and the metal.

Now the last casting step, melt the metal. The tin can be melted with a butane torch. You may need an insulated oven to melt higher temperature materials such as aluminum.

Clean off the top of the tin. I used a handle of a spoon to scrape off the top layer.

Carefully pour the metal into the plaster. Definitely wear eye protection and you should also where heat protection for your body and hands. The metal can splatter and cause serious burns.

Let the metal cool in the mold. You may want to quench the metal to create a different microstructure in the metal, but I did not for this. I let it cool for 1 hour.

Using a chisel or screwdriver and hammer break away the plaster and admire your metal casting.

In this example we made the original mold with ComposiMold, but you can also use the ImPRESSive Putty. Here we show you a quick demonstration of how you use ImPRESSive Putty, a higher temperature capable materials to make the wax casting. After you have the wax casting, the process for making the ComposiMold plaster mold is the same.

Let me know what questions you have. I’d love to see what you make.

Here's the basic process for lost wax metal casting using plaster, beeswax, metal, and ComposiMold:

1.Mold your master object with either ComposiMold or ImPRESSive Putty.

2.Make a wax or ComposiMold casting of the object using the mold you made

3.Make a ComposiMold Plaster Casting of the wax or ComposiMold casting

4.Melt out the wax or ComposiMold

5.Melt and Pour in the melted metal into the ComposiMold Plaster Casting

6.Break apart the plaster and admire your metal casting

You can repeat this process using the reusable molding materials. So now we’ll show you the process.