In reading numerous forums, there are numerous theories on how to paint ELAPOR (Multiplex's foam). The material is very flexible and apparently hard to paint. If you spray paint too close - foam will get wet and damage the foam (it will bubble up), other risk is that the paint job chips off easily due to either adherence problems (special coating used by Multiplex) or the flexibility of the foam itself versus flexibility or inflexibility of the paint itself.
For Multiplex fans - here is the official answer I received from Multiplex USA. Not really a solution but they did answer none the less. As a side-note most popular paint recommended in various forums was Krylon (not H2O version)
Thank you for choosing Hitec/Multiplex products. We are looking in to putting a FAQ on painting the Elapor Foam (NOTE: I suggested a painting FAQ in my email to Multiplex) . We have found that simple over the counter spray enamel like you would find at Home Depot, works just fine. Keep in mind that you are painting foam, and that the paint can easily be scratched off to a new layer of foam. Also, very intricate paint jobs are very tough, as masking over pre painted areas can peel up the paint underneath the masking. As for a primer, I would look to see what some of the guys are using on the forums as we do not use the primer in an effort not to weigh down the aircraft too much. Also, when spraying, be sure to keep the spray a good distance from the foam as the propellant can damage the foam
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