Sculpting and mold making question

[Walteekin25]

Ok, I want to make a sculpture using a Oil based clay, once it is done could I just use RTV around it like normal or would I have to make a plaster cast? If I could use the RTV what would I use a a wall for a two part mold? I know most people use oil based clay so they would stick together no? Go easy this is rather new and confusing to me.

Thanks,
Girard

 

[Stormrider]

If you sculpt in oil based clay, it wont dry. you can spray it with primer to seperate it from the mold.

The plaster cast you refer to would be your mother mold, though making a fiberglass or plasti paste mold is better.

If your goign to make a two piece silicon the divider can be done in clay, but your going to have to seal your clay first as mentioned above.

Otherwise youll get a stuck together mess.

I used plasti paste for mine, and really found it difficult to work with.

I wouldnt use it again. Id use good old fiberglass from walmart. Probably cheaper, and easier to get where you want it.

Plasti paste is like spreading apple sause on something, and thinking your goign to get it smooth and in the right place.

If your making a helmet mold, you dont need a two part mold, just a two part mother mold.

 

[Walteekin25]

Thanks for the info mate it was spot on. Just out of curiosity what helmet did you mold?

 

[Tim Allen]

Go to smooth-on.com I used all my material from them to do my helmet mold.

Heres a shot of the helmet mold up and almost ready for the fiberglass jacket to support the mold.

and then here is the two piece fiberglass jacket over the helmet mold material

 

[Stormrider]

I made a mold of my mr so i can mod it up.

It turned out good, except the dome is a little thin so it makes a little bit of waves, but im going to cut and sculpt on top of it, so ill fix that before I make the next wave of mold and casts.

 

[Walteekin25]

Tim thanks for the pics that helps alot. I have one other question about the resin process. How do you get the resin in the mold and have it cover the upper parts of the mold? Do you you just dump it in and then turn the mold side ways?

 

[Tim Allen]

Tim thanks for the pics that helps alot. I have one other question about the resin process. How do you get the resin in the mold and have it cover the upper parts of the mold? Do you you just dump it in and then turn the mold side ways?

Well with this helmet is trial and error, there are many different materials that you can use on these sculptures, you can just use some type of resin, or a liquid plastic and slush cast it in. The way we did this helmet was poured in a two part "gelcoat" that sets up in about 5 mins or so, painted it up the sides of the helmet with a throw away brush. The next layer is done with the resin and a epoxy resin filler. Basically the filler turns the liqud resin into a paste or MUD so that it can fill in those tough and brital area's that the fiberglass cant sit into. Last, after the "MUD" is painted into the corners and tough areas, we took the same resin and layed in the fiberglass matte for the 3rd and final layer.

All in all, the process took about 15 mins to lay it all up into the helmet, then maybe 45 or an 1 hour for it to harden and then pull out of the mold.