how does PVA react to having a clear epoxy surface coat brushed over it?
What are your concerns, that the pva will come off when you brush over it? On the test pieces I made I just pored resin out of the cup on the mold then lightly brushed around so that the brush always had a front line of resin in front of it. This reduced any friction or contact from the brush and pva to zero. I let it b-stage then infused over it.
I’ve had the same results as Rotorage. Just be careful not to tear the PVA layer accidentally
why is it that you want to use PVA?
I was thinking maybe the pva offered less friction for the epoxy surface coat to flow out evenly.
are you making a tool or part? I dont see how PVA would help level the surface.
I like using PVA because I have a fear of the resin sticking to my mold. I primer all my molds with 2K urethane primer. Even though my molds are perfectly smooth and I often wax them with paste wax, I’m still scared to destroy the mold. I
2talljohn… i never heard of anyone using primer as a molding surface. Seems odd as there are many good surface coats for mold making available. Not trying to put your idea down though.
I just thought PVA would offer a slippier surface for the surface resin of my parts to flow out and prevent dry spots or pin holes.
I did talk to a rep from Mavcoat today, very helpful guy. He recomended their KCP mold release product. It’s sort of a semi-perm … hardens to a ceramic like hardness and is very slick. I was thinking sounds like Frekote NC-770… only thing he could say was KCP smells less and it leaves zero trace on the pulled part… medical industry uses it. Pull a part out of the mold, then straight to paint with no contamination. It runs $100 per gallon, 5 gallons for $400. But those liquid spray on releases go a long ways. Green/new mold coat it 6 times with 15 minutes between coats… let the 6th coat sit for 8 hours before using the mold. Reapply every few parts, one coat.
The semi permanent releases we use make the surface so slick that can slide masking tape on the surface like it was paper. I have never stuck a mold using semis, and after the surface needs no post finish other then a light buff to give a higher shine
Ooooh that would work real well! Since many of our molds require post work (surface putty and what not) to give it a smoother finish, we have to primer our molds. Would you guys recommend me spraying a tooling gel coat with surfacing wax instead of primer? Then wet sand, polish, and spray the permanent release? For the permanent release its best to have the smoothest mold possible with zero pin holes and voids correct? Can somebody direct me a website please?
John
What is it exactly that you want to do? Repair the moulds, or make your products in such a way that they can easily be re-worked?
Since we like to have perfect molds with perfect lips we do surfacing work on all our molds. Add putty here and there, sand this, add more putty here, then primer, wet sand, and wax.
Sorry to thread jack! Back on topic 