can i use brushable mold rubber on clay?

[rgraves]

hi there,
i am sculpting a face out of WATER-based clay and I want to reproduce this. Can I brush on a liquid rubber in order to recast this? If so, would the original clay sculpture be ruined?

Thanks

Rose

[raspero]

First, a caveat: I have never used water based clay. But since no one else has answered you I will put in what I know. I use brushed on mold rubbers, both silicon and polyurethane, on oil based clay, (modeling clay).

Unless your clay figure is dry, (hard), you will not be able to save it; pulling the rubber off totally disfigures the original.

Check the tech sheets at Smooth On, http://www.smooth-on.com/index.html

or at Polytec, http://www.polytek.com/products/poly_mold.html

or call Artie at Douglas and Sturgess Sculpture Suppliers in Richmond CA 1-888-ART-STUF for which rubber to use regarding water compatibility.

R

[Landseer]

The Smooth-on rubber I use can be used over moist clay, Ive done it, works well, but you have to be carefull when brushing it on not to push into the clay with the brush and damage the details.
It has to be covered completely with rubber so no clay is exposed to the air which might start drying it out and shrinking the clay before the mold is done- not likely but possibility is there.

The rubber came off the clay model with zero damage to the clay

[Landseer]

Unless your clay figure is dry, (hard), you will not be able to save it; pulling the rubber off totally disfigures the original.

R

I had no damage whatsoever to my angel panel pulling the rubber off it...
it all depends on how FRAGILE it is and how deep the undercuts are

http://www.youtube.com/watch?v=sVVJJU_Y6vE

[timblacktim]

Yes...if u fist cover the clay in shellac varnish....i did it with a cheap plastic spray bottle....the shellac is expensive tho....but u cant get it off your clay....but your clay is only temporary and not meant 2 b kept is it?

check out Ron meuck....he does wonders with clay....and fiberglass!

:) Just remember to do a thin coat of rubber 1st then thicken the 2nd coat and get it to an even thickness of about 6mm all over......to help u see ur 2nd coat just add a bit of colour pigment...it rely does help.

[GlennT]

Don't know how different the water clays are from oil clays in this regard, but for oil clay I just spray it lightly with Pam cooking spray as a release agent. Works just fine and is about as cheap as it gets, and non-toxic.

[Mordachai]

just a few thoughts
water clay works great when sealed, I often use shellac as mentioned above, but thin it with denatured alcohol, up to 50/50. This will help reduce the shellac and prevent it from filling in fine details, but still give you even coverage and sealing properties. I usually give a few coats with adequate drying time between coats. Also sealing it will slow down the drying of the wet clay. (and I think shellac isn't that expensive- $15 +/- for a quart of the best stuff, and another $7 +/- for a quart of denatured alcohol, you'll be surprised at how long it lasts.)

oil based clays will work without being sealed, as long as they are sulfur free. If they have sulfur they too will need to be sealed.

of course either method will require release, and a steady patient hand when applying your 'face' coat.



I've also had no problems with pulling the mold and damaging a clay model. if you made the mold right, and there are no serious neg. draft angles/undercuts it should come off without a hitch.