"How to Stop Foamcore Building from Warping?" Topic

I've had bad luck in the past making foamcore buildings. I've been painting them with water based acrylic paint as a primer, prior to doing anything else to them. Even the ones I just leave primered and dry brushed warp…I thought the water based acrylic as a primer would *stop* them from warping. Anyone have any ideas on this? What do you folks use on your foamcore? Thanks!

Hmm. I haven't had a problem with them warping. I don't know if it has anything to do with it, but I prime my buildings with gesso.

Fix them into place before painting and dont use long unsuported lengths.

Pretty much anything and everything that contracts when it dries can and will warp foamcor under the *right* circumstances.

If you have to use long lengths then paint it in bands at 90 degrees to the longest length and do both sides at the same time – the contraction forces should equal out then.

you can put the first coat on both sides at the same time.
I seen big buildings pull them selfs apart when only painting on one side.

I read something one time about doing shallow parallel cuts on the inside wall along the length. I'm unclear how this stops warping but it's worth a try.

Otherwise try spraying.

Use gator board in the future— it's a form of foam core in which the foam is far denser so that it's much more durable and doesn't warp at all.

nazrat, by the name, I'm gonna assume gator board is available here in the US…where can I get some to try out?

Here's one place: link

I'm unclear how this stops warping but it's worth a try.

Same way as painting in stripes does – it prevents the contracting forces from operating across the whole of the section and confines it to smaller lengths over which the forces are not strong enough to produce a warp.

Remember that the actual forces are very small and will only warp over an extended unsupported surface in a cumulative way. Break that up and it wont warp.

You can, however, succesfully warp pretty much any foam-board, MDF and plywood with paint or glue, but once you understand how it happens it is relatively simple to avoid.

it's a form of foam core in which the foam is far denser so that it's much more durable and doesn't warp at all.

It *will* still warp, just that the fibre covering is more resistant to it than a paper lining – take a big enough unsupported length, paint it and it will warp just fine.

The "theory" applies to most any material.

Flashman gave you just the place. I'm sorry to say I couldn't have helped you with that, as I have a buddy who works in a printing shop, and they have tons of scraps from mounting posters and such. I have piles of the stuff waiting for the next big project… a Pulp style city.

Don't use foamcore..

Personally, if it is worth building and you want it to last, I'd go with 1/4" hardboard instead..

Nazrat said…
I have piles of the stuff waiting for the next big project… a Pulp style city.

So, when are we starting on this already?

Hmmm. Is there no product you can use to cover the foamcore before painting that will prevent warping?

You can use foam core faced with styrene instead of paper to eliminate warping completely. This stuff is kind of expensive though and can be hard to find. Check sign making companies for scrap. If you only need small quantities, try googling Perfic Panels.

I've never had a warping problem with paper backed foam core, but I heavily spray prime all my stuff. Exposed edges of the foam core may melt a little, but you should rarely have an exposed edge on a properly made building.

"So, when are we starting on this already?"

"We?" Whattaya mean WE, paleface? 8)=