Painting pink foam tunnel portals

the easiest and the only way:

 first you must use waterbased acrylics.  it would be great to see the raw portals, BTW.

I am assuming that you embossed the pattern into the Styrofoam.

 yt9ou will want to first use a light gray fairly solid [paint. thick house paint or from a tube is good for this. using a sponge stipple the surface of the thick paint to add texture to each "stone"  once dry you can use washes of color ranging from tan to browns to a darker gray. this is dependent upon the region you are replicating. the best paint for this second stage is the $1 plus tubes of craft colors in places like wally world, michaels and AC Moore.

a couple of shots of foam portals from founder's mountain at NJ hirailers.

This is what I will be painting

Flat wall paint from Home Depot.  I bought a quart of gray and use it all over the layout, I just tint it with some cheapo acrylic black from the craft store if I need it darker.

Medium gray flat latex house paint, a wash of black for shadow detail, then drybrushing with an antique white for highlights.

Jim

If you first coat the foam portal with Woodland Scenics Flex Paste, C1205, you can use any paint.  Per W/S Flex Paste catalog feature list..."Use to create a hard surface or as a filler or primer on foam."  I've done this for years for three reasons: I don't necessarily like the foam surface texture in the final finished item, any surface abrasion to the painted foam can result in the base foam (pink, blue, etc.) showing through, and I'd rather not have my carved foam effort instantly 'melted/destroyed' by an accidental choice of incompatible paint.

But, as usual, that's just this man's opinion/experience/preference.

FWIW....always.

KD

expanding this post,  for those just starting to experiment with foam.. what techniques do you all use for shaping the foam?

 me: I will first cutout my rough shape with a hack saw blade.. then draw in the "mortar" details with a sharp but rounded pencil , for O scale a carpenter's pencil works very well.

 to add texture to the individual stones, I use a variety of techniques, including wire brush , sandpaper and even dental picks, you cn aeven hack at it with rough sandpaper.  finish the foam with a generally fine grade sandpaper or even a scotchbrite. 

for additional texture stippling with a clean up brush or those cheap touch up brushes with thick house paint works great.

finishing with water based paints is an absolute regardless of priming.

I think the type of foam being used has much to say about the technique being utilized.  Personally I don't feel the newer XPS foamboard shapes as well as it used too.  The Owens Corning foam used to be pink... now its purple.  I don't like it as well.  EPS Foam is a whole different animal altogether.  I also priced some Dow Trymer foam.  At about $185 for a 4x8x4" sheet, I won't be able to use that material.  Guess I'm stuck with my purple Owens Corning.

I needed to match a Lionel plastic portal:

Mixed black and white hobby acrylic (from WalMart) to get in the ballpark:

Then adjusted with other colors of the same paint (I forget which colors--did it by eye), and finished up with a brown I/A wash:

I agree some very nice carving.  Those portals look great!

The one shown is the first one I did. The rest will be better!

A really sharp thin knife following a straight edge was used for cutting the portal out. The top ledge was cut out to fit on top and glued in place with Elmers carpenters yellow glue.

I found that scribing the blocks worked best by using an x-acto knife to score the foam. Then use something that is a little larger, smoother and rounder to follow the scored lines to show depth of the blocks. That way the foam did not pull apart.

I have ordered the Woodland Scenics Flex Paste to coat the foam with and then will paint like you have all said to do.

Stay tuned!

BTW:  Nice to see a fellow Super-O enthusiast around these parts.  The best track needs the best scenery.