Foam Problem HELP!!

[John Busby]

Hi guys

I have a problem I cut some foam with a hot wire cutter getting what I thought was good finished surface.

So painted it straight away.

The problem arose once the paint was dry lots of white spots, much to my surprise the white spots are little tiny holes in the foam this is the first time I have had a foam sheet that looks OK once cut with a hot wire that well wasn't.

Would Gesso cure this or do I have to coat it with something a bit thicker like wood filler or Polyfilla (Pollyfilla is a brand of patching plaster for filling cracks in plaster walls)

I just happen to have some Gesso.

regards John

[dwbeckett]

Try what you have on a sample if it works for you then use it.

[altterrain]

Hi John,

What type of foam are you cutting? and what are you painting it with?

 -Brian

[John Busby]

Hi altterrain

It's the white polystyrene foam my fridge and freezer where packed in when they where delivered.

The paint being used is Citadel acrylic paint the stuff sold for painting Warhammer figures, I am using that because I know its foam safe 

It just happens to be the right colours for what I am doing inspite of some of the weird names.

regards John

[fontgeek]

I would say try the gesso, and then, once it is thoroughly dry, give it another coat with the acrylic you used the first round. Depending upon the intended project, I typically end up using a basic house paint style latex for the initial coat. A heavy all over coat of paint lets the paint bond to itself and seal in the foam.

As silly as it may sound, always make sure your surface is cleaned of any dirt, oils or grease before you try applying paint, especially water based paint. A simple bath using a dishwashing detergent should remove any contamination. Oils or greases will cause a fish eye or pox marks when you paint.

[altterrain]

I'll second that advice, especially using latex paint even if only for a primer coat.

-Brian 

[John Busby]

Hi Guys

Thanks will let you know how I get on.

regards John

[John Busby]

Hi Guys

Well the results where positive I had an historic site entrance made of the same foam that the problem showed up on to do.

It was washed and dried & I washed my hands as the pieces are relatively speaking small.

It was given one coat of gesso and left to dry it was constantly checked as I was unsure of drying time for the gesso, once it looked dry it was left a bit longer just to be sure.

Then it was given a coat of the new Citadel foundation paint this is slightly thicker than normal model paint and gives good coverage on the first coat.

The result was I still have a couple of white spots and blemishes but nothing like what drew my attention to the problem in the first place.

So the conclusion I draw is it works but needs two coats of gesso with a very light sand in between and that should give a good surface to paint on.

regards John