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"Question about vulcanized molds" Topic

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Alex Johnston13 Sep 2020 10:10 a.m. PST

Hey everyone,
I am a fairly new sculptor in 15mm and I tend to do green stuff over a wire armature then super sculpy on top of that. Does anyone know if it is still possible to make a vulcanized mold for metal casting with this material? Also what sculpting materials do you all use? I prefer the way polymer clay works over epoxy putty but I also want to be able to have my sculpts casted.



jwebster13 Sep 2020 10:22 a.m. PST

Anthony Barton uses Fimo


martin goddard Sponsoring Member of TMP13 Sep 2020 10:44 a.m. PST

Hello Alex
Your green stuff will vulcanise just fine.
The heat of the vulcanisation process will cause your master to fall into parts after the mould is separated.
This gives you a great mould but a master in pieces.
Keep the first few castings.


Bunkermeister Supporting Member of TMP13 Sep 2020 11:25 a.m. PST

These guys are good about answering questions, sell all the stuff, and even give classes.

Mike Bunkermeister Creek
Bunker Talk blog

DyeHard13 Sep 2020 2:54 p.m. PST

My experience:

Epoxy type masters (green-stuff, Kneadatite, Milliput, JB-Weld) will survive vulcanizing but will crack.
I have used AC (Super-glue) to seal cracks and vulcanized again with OK results. Cracks reopen.

Polymer Clay (Fimo, Sculpty,…) is not temperature stable. It sort of melts and burns in the process. So, I would not use this if you have a classic vulcanizer (both high temp and pressure). You will see that Anthony Barton, while sculpting in Fimo uses RTV rubber to make molds. RTV = Room Temperature Vulcanizing, which is very different than classic vulcanizing. It involves mixing two parts that react chemically.

Many RTV rubbers do not handle the temperature of molten metal. So some care in selection is needed. The linked page above is a fantastic source:

DyeHard13 Sep 2020 3:33 p.m. PST

I found these really old-school way to cast:

This is from the model railroad perspective, but the process is the same as was used for figures.
The call sculpting the masters "Making the Patterns"
It goes through a stage of making wax copies and brass casting masters, which will hold up to vulcanizing without distorting.

Then they explain in great detail how to take those casting masters and making molds and casting:

This is a much more home-made one using RTV and gravity molds (no centrifuge):

LeonAdler Sponsoring Member of TMP16 Sep 2020 2:28 p.m. PST

If you use silicone moulds Masters tend to survive much better. Shouldnt have a problem with 15mm stuff I have 6mm,10mm and 20 mm come out intact most times just the occasional bit has been gripped by the silicone and gets left behind when the master removed.
Use milliput and occasionally Green stuff over metal armatures on the whole.

Alex Johnston17 Sep 2020 7:10 a.m. PST

Hey everyone thanks for the responses, I had a delay for new members before I could post a reply. So it sounds like my two best options are rtv molds or figuring out how to make a new master out of a silicon mold then use that for a vulcanized mold.

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