More Epoxy Questions

Hello to all, I am considering building a board using a blue extruded polystyrene blank. I have followed all the recent discussion on Swaylocks regarding such issues and have found the information posted as very useful background. I am considering the three following processes. 1. Lamination with non-UV epoxy Paint entire laminated blank in acrylic paint? Hot coat in Polyester Paint entire board in acrylic paint? Gloss coat in Polyester 2. Lamination with non-UV epoxy Hot coat with non-UV epoxy (with colour additive?) Gloss coat with non-UV epoxy (with colour additive?) 3. Paint entire blank with acrylic paint? Lamination with UV epoxy Paint entire laminated blank with acrylic paint? Hot coat with UV epoxy Paint entire board with acrylic paint? Gloss coat with UV epoxy As you can hopefully see from these three process options I am trying to disguise the colour of the blank and produce a board that will not “yellow” excessively with UV exposure. But I am unsure of which stage I should paint (options 1 and 3) the board at to reduce the possibility of delamination between layers. Or can I not paint it in its entirety at any of these stages? Any suggestions, comments and advice as to the pros and cons of these processes (and the painting stage opotions) would be greatly appreciated. Thanks

If you use an realtivly UV stable epoxy I don’t think you will have any problems with yellowing, not more then with a reular poly/PU board anyway. You can also use a laquer finnish with an UV filter. If you do a tint lam or opague lam it won’t show either(unless you do a blue tint and it turns green over time…) If you absolultly want to paint the board I would do it on top of the sanded hotcoat, then gloss(or laquer) over it. If the gloss starts to chip you still have the strength of the board intact. You could paint on the blank, but my guess is that the blue foam will soak some paint and you will be less then happy with the results. You can always try it on some scrap pieces first just to check. Good luck. regards, Håvard

Use #3. Paint the blank with acylic white and laminate hot coat and gloss with a UV stable epoxy. Use Additive F in the gloss and hot coat if you have access to it.

Thanks for the advice Havard and Greg. Much appreciated. Cheers

Rohan, I just finished Airbrushing the bottom of my blue (extruded polystyrene) blank. To me it seems to work pretty well although the lightblue colour of the blank does influence the colour a little bit. I’ve used airbrush paint from a company called Createx. They’re water based. Also I don’t think You get quite the same lustre in the colours as if sprayed on a white blank. Please have in mind that I’ve never used an airbrush gun before, but I really enjoyed doing the spray job. I will use uv- stable Sp systems 115 epoxy for my glassing. /Erik

Thanks for the info Erik. I also forgot to ask about board thickness with polystyrene/epoxy. I have heard that they are a lot “floatier” than polyurethane/polyester boards and therefore should be made a little thinner than regular board dimensions. Is this the case, and if it is, how much thinner should they be? Thanks again.

Rohan I don’t really know about how much better the xps board would float. I think they float higher because the foam has a lower density. The foam I’m building my board from has a density of or weighs 28kg/cubic metre, i don’t know the density of Clark foam? /Erik

I think Greg L. stated about 1/8 of an inch thinner for an EPS board to compensate for the foam being corkier. Not a big deal IMHO. I would check the archives though if you want to be absolutly sure. regards, Håvard

If you are worried about using an expoxy hot coat for waht ever reason(expense, hard to sand??? Here is what to do Lam in epxy, hotcoat in polyester, sand, paint, gloss.

Thanks to all for your help. Very greatly appreciated. Cheers Rohan