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Topic: Spraying Polystyrene
Message: Posted by: magicmarkdaniel (Jan 7, 2008 01:26PM)
I'm going to be spraying some polystyrene eggs for pantomime. Can any craft spray be used for polystyrene? The eggs won't really be handled, most of the time they'll be sat in a basket on display so not too bothered about whether the spray will rub off easily or not.


Message: Posted by: EsnRedshirt (Jan 7, 2008 03:08PM)
Most aerosol sprays will dissolve styrofoams like polystyrene. You can buy "foam-safe" sprays, but a cheaper solution would be to coat them in a mixture of white glue and water (about 1:1 or 1:2) and let it dry, creating a protective coat which will help keep them from melting under the spray paint.
Message: Posted by: magicmarkdaniel (Jan 7, 2008 03:09PM)
Thanks for the help. Will do that tomorrow. I thought I remembered reading that the poly would melt but couldn't find the thread.

Message: Posted by: gaddy (Jan 7, 2008 04:30PM)
Paint the eggs with Gesso (a primer, available at art stores) first. then you can spray the polystyrene safely.
Message: Posted by: magicmarkdaniel (Jan 7, 2008 04:47PM)
Thanks Gaddy. Will weigh up my cheapest options when I buy the eggs tomorrow. Don't want to spend too much on this as I've pretty much spent the budget on props and staging, and still have things to buy!!

Message: Posted by: Thomas Wayne (Jan 7, 2008 07:18PM)
Two words: Bin primer.

Message: Posted by: ClintonMagus (Jan 8, 2008 07:49AM)
There is a difference in painting styrofoam (expanded polystyrene) and sheet or cast styrene.

In my model railroading experience, the only paint I have ever had trouble with on sheet or cast styrene is lacquer. Oil-based enamels and acrylics all worked well when applied in light coats using an airbrush. Lacquer tends to "craze" the surface of the styrene if used without a primer.

Two brands that I used most were Accupaint and Scalecoat. They came in various formulas for different materials, and both companies make an appropriate primer for plastics.
Message: Posted by: magicmarkdaniel (Jan 8, 2008 11:34AM)
Well, I went with my cheapest option - PVA glue/water mix, let them set for a couple of hours and then sprayed. They went fluffy!!! I think my PVA/water mix was wrong, looked a little too watery but hey, from stage, they still look like golden eggs! Think I'll be leaving polystyrene well alone for a while!!!

Thanks for all your help

Message: Posted by: gaddy (Jan 8, 2008 04:55PM)
I used to do a lot of custom modeling in my youth, and expanded polystyrene was a great material- cheap, light and versatile. It does take some finesse to work with, though.

Glad it worked out for you as well as it did...
Message: Posted by: EsnRedshirt (Jan 10, 2008 10:27AM)
Sorry they went fluffy on you! When I worked with styrofoam and white glue, it worked well for me, though I did use at least a 1:1 water/glue ratio and made sure everything was heavily coated.

As I've said before, always test on scrap when uncertain... Better luck next time!