Need casting help

[Vangoghinc]

I just finished my 2nd clay sculpture ever and wanted to cast a few parts of it from my Van Aken plastalina oil based, that claims to contain only minute trace amounts of sulfur. I would need help/tips/tutorials, I guess something easy and cheap for a newby.
Thank you very much!

I have to learn how to post pics from my phone, sorry.

 

[BrundelFly]

Yikes..Most RTV silicones do not like sulfur. You could do with an alginate, then do a plaster casting.

 

[lmgill]

Spray paint it. It works as a barrier coat.
Sculptors "Crystal clear" sculptures all the time, and pigmented spray paint is the same thing, but if you use a colored spray paint, you can see exactly how much paint you are applying over the surface. Which you can't with a clear paint and no, it won't fill in all your detail, unless you flood the sculpture with paint. We do this all the time.
I would strongly suggest Krylon brand and avoid gloss paints, try a semi-flat/ satin or a flat color. Also, like with any process you are unsure of, Test it on a separate sample:
Take a scrap of the clay in question and paint one sample and leave another bare and mix a small batch of silicone and test the samples. You will have your answer.

Also, in a pinch, if you do not have a silicone mold release you can use spray paint.

 

[Mr Mold Maker]

Definitely what @Imgill said.

I used to use Kyrlons primers all the time instead of crystal clear. The Ultra-flat grey primer was ready to mold in minutes. Something not everyone knows is often time Chavant NSP green, for whatever reason, carries minute traces of Sulfur too and it's a very favored clay for many sculptors. A good Sealer is generally all you need to successfully mold it. I would still recommend a release, of course.

It is worth noting two things: One, Inhibition will be less likely with a Tin silicone than it would be with a Platinum. It's very rare for Tin to be inhibited by anything, but it's certainly not unheard of when dealing with Sulfur. Two, the faster your cure time, the less likely inhibition becomes.

 

[Vangoghinc]

BrundelFry, I read about the alginate and they say it's only good for 1 time only casting, is that your exp.?

Mr Mold Maker, Iv'e been reading about tin sil. 80, could someone explain the hardness option I should use.
3 individual product options. Shore A15, A30 & A40 hardness options.

And which primer should I use? I have: Valspar int./ext. primer and Rustoleum auto primer?

Thanx guys!

 

[Mr Mold Maker]

It depends on what you're molding, but Shore A30 is usually a good general purpose mold rubber. Basically, the lower the number the softer the silicone. So a 10 is a lot softer and stretchier than a 45. If you're casting a piece with few undercuts and smooth details, A30 will be fine. If it's something that has undercuts and sharp details.. meaning places where the silicone curves into and wants to lock to the model, you may want something a bit more stretchy like A15.

 

[Vangoghinc]

I'll look into it. Thank you.