Best way to seal (blue) hi density foam?

[Donal]

I've made some large dioramas, only recently starting to use hdf that I needed for clean straight lines.

On the last diorama, the problem I encountered was how to seal it PRIOR to painting (airbrushing).

Pollyfilla (spackle) blurs what I tried to do if it was thick enough to be effective. Using it thinner and painting it on didn't give sufficient protection as I wanted to add either a varnish or aerosol paint layer afterwards.

I was looking for a particular finish which required a smooth surface which could then be painted.

My next major diorama will have the same problem.

I has some success with painting on a layer of acrylic paint but wasn't entirely happy because i needed a smooth surface, and ever very fine sanding was too abrasive.

Searches haven't led me to a solution and it's a product I'm not familiar with.

Any help appreciated.

 

[airhead]

gesso is designed to fill the pores of canvas and provide a smooth surface for painting.

GW spray cans are water-based paint and would work. (finally a use for GW paint).
Krylon water based is cheaper if you can find it.

 

[freakinacage]

GW spray cans are water-based paint and would work. (finally a use for GW paint).

is that a new thing? i have used them in the past and they have dissolved the foam

 

[supervike]

I know I've sealed some of my foam by using a spray/mister type bottle filled with a mixture of white glue and water.

That would prevent any aerosol from eating it, but I don't think it provides the smoothness you are after. Maybe multiple coats would?

 

[Donal]

i was surprised about GW spray answer.I pretty much stopped buying GW 15 years ago though. And I'd prefer not to buy their overpriced paints or accessories. I'd feel I was implicated in corrupting kids.

I have tried other acrylic spray but the transport medium does dissolve the foam. I would have suspected this to be the case for all sprays. I use an airbrush also, but acrylic applied that way will not seal the pores.

The white glue idea I wonder about as providing a base for future paint work.What kind of surface resulted?

Kylon is not available here (europe). Gesso might be worth trying though.

 

[Valander]

gesso is designed to fill the pores of canvas and provide a smooth surface for painting.

GW spray cans are water-based paint and would work. (finally a use for GW paint).
Krylon water based is cheaper if you can find it.

I'll throw in another vote for gesso. Works great for sealing up the foam, and you'll get extremely little detail loss, and a very nice surface to paint on.

The Krylon H2O line of latex spray paints is also a good option, and you can get it in several colors. They usually tend to be a little glossy, but since they'll seal up the foam, you could always finish with a matte spray anyway.

 

[freakinacage]

masonry paint would work. i use the textured stuff to cover styrene for concrete. the smooth stuff could work for you. works as a primer as well as it is coloured, unlike pva, and makes the styrene hard as nails, has some real strength and flex

 

[airhead]

If you are doing a large scale table (4x8, etc), get a gallon of house paint (interior). Most any brand at most any home center. Water based latex. Small roller and you are in business.

 

[nels0nmac]

An alternative to the paint solutions mentioned above would be to cover the foam with Cascamite.This is a powdered resin based glue that you mix with water to create a paste. Because it's resin based it doesn't need air to go off so is great for sticking slabs of blue foam together. It dries rock hard and although I haven't tried it it probably sands quite well. You could thin it down more than usual and apply a thin coat over the foam. I think it takes about 24 hours to dry and is then completely waterproof, and spray proof as well. Best to test before hand though.

 

[Spittle72]

Water Based Polyurethane.