White index card showing original coins and coins made with silver-colored InstaMorph moldable plastic. Also shown are the red molds used to create the coins.

Casting Low Temp Metals

Spence did some really interesting experimentation with InstaMorph and low temperature metals. Here, he shows us how to make metal castings at home.

“Typically, molds are made out of metal, and used to cast plastic. Well, I figured it would be fun to do it the other way around! Fortunately, there are a few metals available which melt at a lower temperature than InstaMorph; I used three of them:

  • Gallium (melts at 86 F )
  • Bi-Pb-In-Sn-Cd eutectic (melts at 117 F, sold as “Cerrolow 117”)
  • Bi-Pb-In-Sn eutectic (melts at 136 F, sold as “Cerrolow 136”)

Note that although those alloys are commercially sold under the Cerrolow trade name, my samples were prepared at home.

I first dyed the InstaMorph orange (so that I won’t accidentally mix it with other InstaMorph after using it to cast metal in, can’t be too careful.) for making the mold – the coloration also makes it easier to visually inspect the molds for damage and structural integrity. Making the mold for the small ingots – yes, the form I’m using is 5 pieces of gum glued to a piece of aluminum.

After making the molds, I put the metal I was casting into a plastic syringe, heated in hot water until the metal was fully melted, and then dropped it into the molds. I first made a proof with gallium, to see how well the whole thing worked without risking damage to the molds. I then performed a similar process using the 117F alloy.

After the molds survived this, I did the same thing for the 136F alloy, expecting that it would cause some damage to the molds, since it would be very close to the melting point of InstaMorph when it was poured – but the molds came through with no visible damage, and the final results are shown below. Note how well the detail on the face of the coin was transferred to the coins.”

Note: Some of the metals mentioned in this article can be toxic. For instance, “Cerrolow” contains lead (Pb). Please use the proper precautions when working with these materials. And, it’s probably a good idea to only use the InstaMorph for metal casting after doing this, like Spence suggested.

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