"Painting Polystyrene (aka "The Pink Stuff")" Topic

I've decided to try my hand at creating terrain with Polystyrene insulation. Since I'm a novice at this, _any_ advice on this would be most welcome. Specifically, I'm wondering about painting the Pink Stuff. I assume that it doesn't need priming and that acrylics work as well as enamels on it; also, I understand that spray paint will cause it to disintegrate. Is my thinking correct on these matters?

Thanks!
Doug

yep.

If you're going to be using a large amount of one color to paint the terrain I'd pick up some latex house paint at you local DIY store. This is what I did for some city terrain boards a while ago, had them mix up a nice shade of gray. When I needed to shade or highlight I'd just mix some inexpensive craft acylics with the latex. Worked great.

I went for the Textured" paint instead of regular house paint.

Just for your info the best places to buy polyfoam(pink stuff) from is FGF Ltd, branches are across the UK.

The alternative to Polyfoam is Styrofoam which you can get from Sheffield Insulations who also have branches across the UK.

If you are going to "glue" sand onto the pink stuff, might I recommend gluing it with paint rather than glue. I don't know why, but I just find it beads less and goes on more evenly.

You can use some spraypaints on foam; it depends on what carrier they use. However, the only way to know whether it's safe or not is to test it on a scrap piece of foam.

You can get interesting effects by lightly spray painting styrofoam at a distance. It does rough it up a bit as it dissolves cells and then solidifies. Test first, and do it outside.

If you are going to flock it, flock it on the SECOND coat. Paint it your ground color first so the pink is covered. I have gotten interesting effects by using different colors of flock. Lightly scatter one color, and then cover the board with another. The shake off and residue is still useable, but as a mixed color.

Keep a note of paint combinations etc and glue it to the underside or side - so when you need to repair those very pink bits of damage you can do it easily.

I usually cover the foam in PVA glue before painting. I find this hardens the foam (especially the edges) and protects it well. After the PVA has dried sand and paint goes on.

Krylon Living Colors are excellent aerosol paints that will not melt the foam.

Yo might be able to use a spray bottle, with thinned housepaint/acrylic paint, if you don't want to use a roller, or brush.

I've found light layers of spray paint work best without roughing up the surface too much. If the paint stays wet too long it disolves the foam.

House paint works great. The cheaper the better.

I second the recommendation of mixing sand and paint instead of using glue.

WARNING - anal foam post iminent!

The issue with various rigid foams (styrofoam/styrodur and the various insulation foams) is that the actual density of the individual foam, along with its cell size, will actually dictate to what extent you can use various paints/coverings succesfully on it - it can also change the effect of various glues.

I mention all this as way of explaining why you will get a wide variety of answer on using spray paints succesfully ( or not) and how some people may say one glue works whilst another says it wont.

"pink" foams are usually arouns 20-30kg/m3 (they vary by brand) and have a bigger cell structure and are more susceptible to spray paints (or the accelerants in it I should say). They will work better with PVA or other air-dry glues as the open cell structure allows breathing for the glue to set.

At the other end of the spectrum are super-dense foams of 200kg/m3 which are used to make industrial blanks, surfboards and windsurfaers - this stuff is pretty indestructible.

Inbetween are the "blue" foams - normally Styrofoam and Styrodur (both brand names - note the capital S) which go from about 32kg/m3 up to about 52kg/m3. The high 52kg/m3 is smooth-styrofoam with a tiny cell structure, smooth texture and which you can even use superglues on with success without melting. 40kg/m3 and 32kg/m3 (which are the usually european weights for insulation styrofoam such as "Floormate 200-X" and "Styrofoam LB" will be melted by superglues but may not allow air-drying glues to dry properly ( so use UHU Por or Foam-2-foam) for gluing them.

And just to make things really awkward: the colour of the various foams is now largely irrelevant to actual properties. The colours were orignally developed over time with manufacturers trying to indicate their own brand type by a colour e.g. Styrofoam (brand name) was always blue. Unfortunately this no longer works acurately as you will find lightweight blue foams and heavyweight pink ones - there are now also green foams, red foams and yellow foams all in the 30-42kg/m3 ranges e.g you can now get Styrofoam (brandname) in green.

There are some general rules of thumb though (and for this when i say "styrofoam" i mean all rigid foam not just the brand Styrofoam):

"proper" glues that you can guarentee will stick sheets together are: UHU Por (contact adhesive with high strength contact grab, sandable) and Foam-2-Foam (long setting time, allows repositioning but actually foams the best seal over a 8 hour set time). Both of those types are UK/Euro available - sorry but i don't know the north american or pacific brandnames.

For covering you are safe to bet on any latex-acrylic paint. IN UK/Europe these are generally types such as masonry exterior paints such as Dulux Weathershield... but any latex-acrylic paint will grab styrofoam without an undercoat needed, it wont melt any styrofoam (or even expanded polystyrene) and has some inate flexibility that works well with the flexibility in the foam itself.

On the simple premise that unless you know the exact density of your particular foam AND you know the exact propellant of a spray paint - DONT use any spray paint on a foam even if it says it is "ok for use on styrofoam" - because what they call styrofoam might not be what you ahve been sold as styrofoam.

Thus: always test a small section by spraying an offcut up close with the spray paint. Doing it upclose ensure you hit the foam with a good dollop of propellant - if it doesnt melt then it never will.

And, just to give an idea of the variations out there - we have access to 72 different types (brandnames) of "styrofoam" within the UK only - ALL of which are fine for modelling with, depending on final use... but many of which act entirely differently to the others.

If you've read this far though at least you will now know why you see so many varied replies and results using various spray paints and glues: "sytrofoam" is not always "Styrofoam".

I have recently seen a line of "foam safe" paints and glues sold in the US Hobby Lobby chain. Next time I'm in there, I'll check the brand name. I also recall using a foam safe version of Liquid Nails construction adhesive.

Like others have said, latex and acrylic paints are normally benign when used with styrofoam. Many spray paints use toulene, MEK, acetone or xylene in their formulas and these are all solvents to styrene. As Antenociti says, density and cell structure of the foam have a lot to do with how well it will survive contact with these solvents.

Hmmm... 200kg foam. That sounds cool!

For my latest project, I am using 2' x 4' sheets, (1" and 2" thickness) of white styrofoam. I'm painting with a new (I think) brand name from Krylon called "H2O", which is a latex spray paint. First, I actually "flick" a small amount of acetone for texture and let it evaporate. I'm using a dark brown color of H2O for coverage, then varying the density of the light brown/tan top coat for the final look. Since the white styrofoam is fragile, I am hand brushing a top coat of "Mod Podge" to add strength. This stuff looks and smells like common white glue, and dries clear in a few days. Even though I chose the matte version, it was still glossy, so I top coated with matte spray acrylic. To protect the edge of the board from abrasion, I covered that with duct tape (which also protected any overspray damage from the varnish). If you can't find the H2O Krylon, look for any latex spray paint and do a test on a scrap piece for compatibility. I am very pleased with what I'm getting for a result. Good luck.