casting over clay?

can i pour smooth on vyta- flex 30 directly onto clay that has not yet been fired?

Pete, why would you like to do that?

copper:

i can make my wall sculpture from clay: then i want to make molds for reproduction:but without firing the clay
is this method okay?

Pete

Well, I have heard of rubber latex being used over unfired clay for molding but I must honestly admit I don't know about vyta-flex

well i have not used it before, but i have looked on smooth on website and it looks like it would do the job i need, i am just unsure of it on unfired clay.
i will ask their tech dept: and i will post back here:
i just wondered if a member had used this method before and could offer any advice.

pete

Members do not always read the questions exactly at the time we need an answer to them (but later when we have moved on, such is the character of forums) - But, I look forward to hearing about your experiences later on. Maybe first try it out on a small 'test sculpture' before applying it on the main project.

NO NO NO.
I hope I'm not too late here.

The Vytaflex will react with the moisture in the clay which will result in foaming in the liquid rubber and bubbles in the cured rubber.
I am sure that is not what you want to happen.

I recommend coating the sculpt with several coats of Bullseye spray shellac to seal the clay; followed by two applications of Universal Mold Release release agent, then you can apply the Vytaflex rubber.

Remember - Moisture is an enemy of urethane materials. May the force be with you.

hey pabrad
thank you for your input.
happily you are not too late {still waiting on delivery} i am in cyprus so i guess any spray shellac/varnish will do?
thanks again.
pete

Thank goodness!
Yes any spray shellac will work; you need to create a barrier between the clay and the rubber.

the only problem with this is the shellac can reduce detail; if this is a concern, you mgiht consider using a tin-based silicone like MOLD MAX 30, which will NOT be inhibited by the moisture in the clay.

If you carry-on with the Vytaflex, you WILL need to use a release agent otherwise the VYTAFLEX will bond to the shellac surface.

Hope this helps!

several coats of shellac & make sure it is dried thoroughly prior to applying release agent;

in fact the best thing to do would be a test between the release agent & the shellac to make sure the solvent in the relase does not screw up the shellac; do this test on a small chunk of the same clay coated with your shellac;

If you go down the MOLD MAX 30 road, crystal clear acrylic spary (Krylon) is used as the sealer instead of shellac as the shellac will inhibit the tin-based silicone.

I made a sculpture with a metal armature inside so I can't fire it. I plan to shellac it, and then paint it (maybe). You suggested Bullseye shellac but I want to make sure this is what I should use. Can you reply to my email in case I can't find this site again? This e-mail address is being protected from spam bots, you need JavaScript enabled to view it

Thank you so much!!