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Posted: May 30, 2007 07:25 AM
exposed foam
What should be done with foam that has been exposed for a week? The majority of time the foam has been under heavy clouds and rain and some periods of sunlight?

I know we should have stopped and installed the primer or base coat the day we shot foam but we were trying to get all the foam sprayed on a Saturday. It has rained every day since and will be exactly one week since we installed the foam until we can get the primer on.


Posted: May 30, 2007 01:04 PM
i had foam that was exposed for a week late last fall, but it was cloudy/rainy and very low uv exposure.Also Im located in north dakota. We made the decision to base coat and top coat it. I inspected it this year, and adhesion is good. Did i commit a sin?
Gerry Wagoner
Posted: May 30, 2007 02:51 PM
It depends.

The safe bet is to grind the skin, or prime it with a good primer.

There are some foams that resist short-term yellowing better than others. VFI's 730 foam for instance can be exposed for as much as 1.5 weeks before coating. Some will endure less than that.

One of the problems with the foam surface is that trace silicones in the resin tend to leach onto the surface as UV works on it. This is part of the adhesion problem, as far as I know. Perhaps a chemist will weigh in on the topic and provide more information.

Posted: May 30, 2008 01:46 PM
next time just do a dust coat of your coating...you can literally cover a many squares in a short time. This light dusting drys quickly and seems to provide enough short term UV protection that you can come in a few days later to finish the job.


Thomas Tisthammer
Posted: May 31, 2008 07:26 PM
What type of coating are you planning on using? Acrylic, for instance, has only mechanical ashesion to SPF while solvent-based coatings can chemically bond with the foam. Fast-sets of any kind will have more bonding problems under the conditions you describe. If your SPF is thoroughly dry & not "dusty" (drag your thumbnail backwards across the surface & check for "rust or dust" on your nail)a medium cure (24hrs) urethane will usually adhere satisfactorily if back-rolled. The conditions you describe occur frequently in my region (the Rockies) & I have to say that I have had very few adhesion problems over the last 30 years in spite of this problem. Contact me directly for more details if you wish but you can make it work if you are careful.

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