I'm planning to make an RTV Rubber mould of my own plaster wall section. Do I need to coat the plaster wall with a release agent or seal it in any way before applying the RTV

No need with RTV rubber, it wont stick to most surfaces besides its self. If you are doing a two part mold then you will need the release agent on the RTV befor you pour the second half or you will never get the 2 parts seperated!

One thing that I do is to prime the plaster with a couple light coats of a good primer, then make the mold. This helps to get the master out of the mold clean.

Hope this helps!

Pat,

I believe you need to seal it before pouring the mold, since you are making a mold of a plaster wall the plaster might soak in the RTV and the mold might get ruined.

But I could be wrong. Whether be safe than sorry.

Mike

I have had it stick before and would seal the plaster first, normally I use tamiya gloss thinned and air brushed on. This gives a smooth surface so the RTV is less likely to stick. Then coat it with the release agent. Because all it takes is one little spot to stick and ruins the mold. I've used the release agent Micro Mark sells with good results.

The links below provide pictures and descriptions of some things I've done with RTV latex.

http://www.themodelarmory.com/statue_article/StatueArticle/StatueArticle/album/StatueArticle.htm

http://www.themodelarmory.com/statues/statues/album/statues.htm

It might have alot to do with the brand of RTV as well. I use Smooth On products and have never had problems with it sticking. But then again better to be safe....

Thanks guys. I'll go with a primer.

Although it might come on a bit thin on plaster, I never tried it on plaster myself, but I have had good experience coating with Future/Johnsons Polish.

Cheers

I always prime my plaster masters with 3 or 4 light coats of Krylon primer, any color. In fact, in a pinch, almost any spray paint will do.

I use Dow Corning 3110 silicon rubber.

Randy Pepprock
www.dioramasplus.com