Foamcore question

I have heard that painting both sides helps.

If the foamcore is solidly glued in position it won't be able to warp.

Water-based paint will warp the foamcore.  I've had good luck with Krylon-like spray cans.

OK; so I should have glued it to the backdrop first, that makes sense.

Tempera is water based; I thought spray paint would disolve foam?

Thanks for the tips guys; back to the drawing board or in this case the backdrop board.

It is only foam on the inside ("core") -- sandwiched between layers of paper.

Dont use form core...  I recommend you use Gater board. It has a fiber face instead of paper and over the last 12 years of using it as backer for my card stock drawings I have not experience any warping.

Les Lewis, at www.westportmodelworks.com

I concur with DennisB and Bob....If you are using it for a model, then gluing it first then painting it with non-water based spray paint should not be a problem.  I have used a lot of foam core for various modeling purposes with great long term success but I have always used oil based spray paint.  And...yes....if you spray the edge of the foam core with the spray paint, it will eat into the foam so this is where you can use a small brush using the tempera paintoin the edge after you have sprayed the flat sides providing that the edges are going to show.

Alan

KD....very good advice on using the Krylon matte as a sealer first if one is going to use a water based paint...

Thanks,

Alan

Thanks folks; I knew I would find a wealth of knowledge here.  Now if I would just ask first! 

I was at the sign shop this am and told them what I had done.  I think the only reason they didn't laugh (out loud) was to make sure I kept bringing them my business.  "How'd that work out?" was the owners response as he hid his grin with his coffee cup. (We go way back.) He then led me to the shop and pulled out some end cuts of Sintra and told me give them a try.  Told me to paint it with light coats of spray paint for plastic letting it dry between coats. 

Got my weekend project now.

Steve,

Also keep in mind that a CA glue will eat the foam if it gets onto it.  If you are gluing the foamcore to something, try Elmer's or white glue.

I've built a number of large 3-D backdrops (buildings) with foamcore.  It needs to be reinforced (I used a wooden frame), and then I covered it with Plastruct or Evergreen sheets to depict the building.  That method yields a strong, light, and durable building.

George

I use Krazy glue gel (CA) quite often to glue things to the edges of foamcore, because it doesn't eat foam.

I don't care what you paint it with it will eventually warp if it's not braced. It may take time, but it will warp. I painted some to use as a photographic sky backdrop, After about 6 months or so you could begin to see it bowing. Some paints work faster, depending on the moisture content of the paint. The bowing is caused by the evaporation of the moisture, this causes the paint to shrink. When it shrinks it starts pulling the outside edges of the foamcore towards the center, thus the bowing.

This is the main reason why I haven't jumped on the foam core bandwagon. Unless weight is a prime consideration, I prefer masonite. Yes, it too can warp if not properly prepared and braced, but much less dramatically in my experience.

Jim

I think the bowing issue also depends on the size of the sheet of foamcore being used.  I have used it in model making (architectural) for MANY years without any problems but it was braced and painted properly.  One reason in my case was it was very economical as well as very easy with which to work.  Cutting out openings is a breeze and it is easily manipulated with a minimum of tools.  Now...for large areas like backdrops, then I would use something other than foamcore because I can see where warpage would be a problem.

Gluing it using carpenters or white glue works great as well as CA glue. 

But, as Jim says above.....hardboard type material like masonite works great and there is no doubt it is more permanent than foamcore.

Alan

I'm using 4' high x 7' long foamcore boardsigns I got free at the grocery store when they were done with them for my backdrop the side with the printing I covered with 2 coats of latex primer sealer (that will be my wall back side) and one coat on the other side (front side) and will paint all the front panels with sky blue latex rolled on., then I'll use spray enamel paint for my different colors, no warpage so far after doing all the priming.

Steve,  Your buddy at the sign shop did you a favor with the sintra.  I am a convert to pvc foamboard (sintra).  I use it to build everything.  It's very versatile.  The price is high, but if you have a source that's free, go for it! 

Nick