Brush molding oil based clay

[spidermanc]

Hey everyone.

I've been modeling in clay for awhile now, but I've never actually molded before. I had access to a kiln so I would normally just fire my finished piece and work with air drying clays. One of my latest projects I worked on using clay was a life size bust in stoneware. It was a hollow piece, and even the hair was sculpted in clay; simply because i didn't have the time, interest, or knowledge to mold and cast it.

However, recently I've been interested in starting a life size bust that I can ultimately cast in silicone, give acrylic eyes, and plug hairs or use a wig (the hair is long and curly, so plugging might prove to be extremely difficult).

I've been watching a lot of videos but I still have a question that I haven't heard anything on yet..

I plan to do a brush on silicone mold once the bust is done, but it seems like if u have to brush the first layer into the piece to make sure you don't get air bubbles that it would deform the details in the piece??

I've never worked with oil based clay so maybe I'm worried about nothing but I know if I tried to brush silicone on my stoneware bust before it was at least leather hard that it would start to misshape all of my detail.. and oil based clays don't dry so that's my concern.

Thanks for any tips & advice!

 

[BornKilr]

Another concern is that many oil based clays will inhibit the curing of silicone, something about the sulphur content of most oil clays. But apparently there are sulphur free oil clays. I've never had this happen personally, since I had read this previous to trying it, but there is information about it on Google.

 

[clonesix]

Do you want to make a silicone mold AND cast the piece in silicone piece? Did I read that correctly? Silicone sticks to silicone, and it might be better to use Urethane for your brush up mold.

With urethane, be sure to use the proper release, as urethane without release, is glue.

 

[JtotheP]

I think a case mold would be better, but that's just me. You can eliminate seam lines and not worry about damaging the sculpt with aggressive brushing to fill in the details. However, doing a case mold would require you to vaccuum out the air after mixing, so if you don't have access to a vaccuum chamber just be careful. If you use a sulfur type oil clay, spray on Krylon crystal clear to seal the clay to protect the silicone from sulfur.

 

[spidermanc]

Do you want to make a silicone mold AND cast the piece in silicone piece? Did I read that correctly? Silicone sticks to silicone, and it might be better to use Urethane for your brush up mold.

With urethane, be sure to use the proper release, as urethane without release, is glue.

Sorry, I meant to say urethane brush on, I don't know why I said silicone LOL :lol.

But still, am I missing something? How do I dab the urethane on for the first coat without ruining the sculpt?

 

[Bondo Fett]

Sorry, I meant to say urethane brush on, I don't know why I said silicone LOL :lol.

But still, am I missing something? How do I dab the urethane on for the first coat without ruining the sculpt?

As JtotheP said coat your finished scupt with Krylon Clear. Not only will it it seal the surface it will harden it slightly. Oil-based clays are much harder than watere clay and brushing on the rubber shouldn't damage any surface details.

 

[Themovieman]

Its not as difficult to brush on your first coats of rubber without disturbing your sculpt as it sounds. I like the urethane the best. Use a good mold release such as pol-ease 2300! If you use a good ,kinda transparent urethane, you can let it run over your sculpt to capture the detail. Plus you can see any airbubbles. Gradually thicken each layer with fumed silica to brush on the rest of the mold. Back with a fiberglass or plaster mother mold.