Hello..... Im making my first styrofoam building. So far it looks good to me. I scribed the bricks quite nicely. When i start painting it, disaster struck !! I was trying to make a wash of dark gray on the line between the bricks (mortar line??). But i think either the styrofoam is too pourous; or something else, all i have now as the result of the wash is, deeeeeep and biggggg line between bricks. Now my ruined building is....well.....ruined....lol.... :-)

What did i do wrong ? Should i gloss coat it prior to washing ??

PLease help...thanks !

I'll wager that your wash was enamel or oil thinned with mineral spirits or "paint thinner."

Incompatible -- these solvents will melt styrofoam.

You need to paint foam with acrylics only. You might be able to use a ink wash thinned with alcohol -- but test it on scrap first!

Ummm yes...

Anyway to give the foam "a protective coat" before painting ?? All paints i have are enamel

About the only possible "protective coating" would be some sort of acrylic. Sealing styrofoam can be difficult because it is very porous. It wil soak up coat after coat of paint.

I would suggest a couple things:

First, go to your local discount store and see if they sell some cheap craft paints. Many of us here in the U.S. have discovered that Walmart has large bottles of acrylic paints for much less than paints from the hobby shop. They sometimes have goofy names like "Country Gray," "Apple Red," "Barn Red," "Sage Green," "Terracotta," etc., but can be mixed easily and thinned with water, alcohol or even windshield washer fluid for washes or air-brushing. These paints are great for foam, plaster, wood -- even plastic. I you don't believe me, look at the works of Anders Heintz, the fantastic figure painter on this site, who paints almost all of his uniforms with cheap, Walmart paint! (I think it's 44 cents for four ounces.)

Also, if you decide to try to "seal" the foam with acrylic house paint or some other stuff, test it on scrap before you put it on something you've worked. Warning -- almost all canned (aerosol) spray paints are too "hot" to spray on foam and will melt it just as badly as your wash did.

I think Hollowpoint is right on the melting and pourus deal.
Here is a good article with foam for building, Check page 3 & 4 specifically (the rest is a good read too)
https://armorama.kitmaker.net//features/142&page=4

Umm...maybe i'll try those cheaper craft arcylic paints.
I just read an article, suggesting that applying a thin coat of diluted white glue might help. I'll give it a go.. Thanks for the help !

If I'm using styrofoam as a base, I like to airbrush a coat of white acrylic as a primer. It helps to seal the work, and gives you a basecoat to work from. I use the craft store $1.99 bottles of paint for my structures. Cheap, easy clean up, don't react with other paints. Sometimes I will mix up a really thin batch of drywall compound and paint the styrofoam with a couple of coats. Once dry, you have a "stone" building you can work with.

Hi, ToonArmy...
Imagine this... You are making your first polystrene model for a submission of your department of architecture and the submission is about 5 hours later at 9 am. You have not slept the last 4 days, not sleeping this night too, it is almost 4 oclock in the morning with bloody eyes, cut fingers and lots of coffee spilled on your clothes... You glue your pieces of polystrene with plastic glue and leave them aside to deal with other pieces... 5 minutes... you hear a sound: "hissssssss..." ... Yes, coming from the pieces you just glued... All lost... In tiny white bubbles!!! Then you go and sleep, you rest in peace... Not even thinking about the damn submission!!! Sad story, but you seem to have learnt the fact in a similar way. Rest in peace friend

Toon army, can you get unibond in Oz thats what I use on poly, glues it seals it the works.