Primers for Signboard

Synthetic sign-board materials tend to soak up the paint and get blotchy. Here are some suggestions for a practical primer. June 8, 2008

I've been finishing for about 2 years and taught myself. I'm doing a small job for a client and the material is called signboard but it's not MDO; it's more like a hard foam and cuts like butter on my CNC. The problem is every primer and paint I put on the signboard just soaks up and is blotchy. Does anyone know of a good primer to put on this substrate, something more like a buildup primer to give me a smooth finish?

Forum Responses
(Finishing Forum)
From contributor S:
If this is not an exterior project, there are several high solids, two component primers available to you - Becker Acroma, Chemcraft, ML Campbell to name a few. I'm unsure on the material type that you need to prime.

From contributor C:
It sounds like it's very bendable also - am I correct? Is it being used in a way where it cannot be bent? If so, then I would use Zinnser shellac primer - this will give your over coats much better hold without damaging the foam. Since I don't know the product, it may be a foam that's attacked by normal solvents. If not, then you could also use 2k poly or even polyester primer, depending on what end results you're after. It may help if you explain the end use of what you or the client wants or needs.

From contributor K:
I don't pretend to know as much about finishing as the resident chemists here, but as a shopfitter, we use this material for interior and exterior signage and for both applications I go to the local motor factors and I use car primer (which has a high solids content) and car enamel. I've never had a problem with reactions with the solvents.

From contributor R:
Contributor K, as someone who is still alive to tell the story, I would have to agree with your choice of finishing products.

From contributor T:
Thank you for the responses. I ended up using a high build primer surfacer by PPG/Shopline, an automotive primer, and it worked great.