PVA - Acetate, Alcohol or both?

Don't want to see this ad? Sign up for anRPF Premium Membershiptoday. Support the community. Stop the ads.

Zlosk

New Member
I am cobbling together a foam part (pink insulation, EVA, and foam in a can) with the intent to make a fiberglass mold. I've read a lot of posts that talk of using PVA as a sealer for the foam. I believe this is polyvinyl acetate.

After applying the sealer, I'll go on to the rondo and sand stage. I should then apply a couple coats of PVA, letting them dry into a film to act as a mold release. I believe this is polyvinyl alcohol. Finally, I should apply a couple thin coats of resin, then start the fiberglass buildup.

Question 1 of 2: Am I correct in believing that I need both forms of PVA?

Also, in the talk of sealing foam, I've seen people talk of using Elmer's glue, wood glue, and modge podge. While at Home Depot, I saw PVA Drywall Primer & Sealer.

Question 2 of 2: Is PVA Drywall Primer & Sealer an acceptable form of PVA, or should I make sure that I use a PVA adhesive instead?
 

Don't want to see this ad? Sign up for anRPF Premium Membershiptoday. Support the community. Stop the ads.

Zlosk

New Member
I'm a bit further along with my project, and question 2 has been answered by testing. PVA Drywall Primer & Sealer is NOT an acceptable form of PVA for sealing foam. I now have True-Bond II wood glue, and should be ready for the sealing step in a couple days.
 

YenChih Lin

Sr Member
sorry being late for the answer: you're right. PVA is Polyvinyl Acetate and unfortunately PVA as name is also the alcohol derivate (better named as PVOH). Most wood glues contains PVA…
 

Fireball Joe

New Member
Your best bet to seal the foam is a few coats of laminating epoxy. You can sand it nice and smooth, then apply your PVA (alcohol) mold release to the form and lay up your fiberglass mold. Are you intending to use epoxy resin or polyester resin for your fiberglass mold? Polyester resin will eat right through any foam it comes into contact with, so whatever you end up using to seal the foam, make sure it doesn't have any pinholes or weak spots. It may be more expensive, but epoxy resin is much easier to work with.
 

Don't want to see this ad? Sign up for anRPF Premium Membershiptoday. Support the community. Stop the ads.

Top