If you want to cast items with metal, like lead or tin, you may find RTV (Room Temperature Vulcanized) silicone rubber easy to work. There are different grades, my recollection is we used 37.
Iit was easy to work. We'd place the master half way into a base of modeling clay. Check that the seams won't cause air bubbles. Make a cardboard box to fit. The base.
Pour out a reasonable amount of the rtv into a cup and add the curing agent. Mix well and pour into the mold box.
In an hour it should be hard, remove the cardboard and the clay, being careful to not pop the figure out.
Thinly paint the rtv with a soapy wash, reattach the cardboard, and pour the other half of the mold.
You may need to create air channels for the air in the cavity to escape
We used pins that touched the figure when pouring the second half.
When the mold has hardened separate the two halves carefully. (This is why you have the soapy wash. Otherwise, the new rtv will bond with the first pour.)
Cut a funnel into the base of the figure for the molten material to be poured into the mold.
The biggest problem we had was air pockets. If the metal didn't fill the mold, we'd use a dusting of talcum powder to lubricate the mold.
Since this is a gravity pour, to get enough pressure for the molten material to fill all the cavity, sometimes it is necessary to make the mold longer. That is to make the pouring spout you cut into the rtv longer. This puts more pressure down the spout.
And after maybe five minutes, the metal has cooled and set. You can trim the air channels, the sprues, with nail clippers and use a file on the seam lines.
Hope this helps.
« Last Edit: July 23, 2021, 04:44:53 PM by besilarius »
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