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question on spary to put on foam


Well-known member
sorry was not sure how to tittle this question :?

I would like the make a smooth casting mold for this gearbox case instead of a rough sided one witch means a little extra work now but it will look better when finished.

On the white Styrofoam you get at somewhere a hobby shop, what can I spray on that to make a hard smooth coat without melting the Styrofoam? I know the clear coat glaze in a spray can melts it :oops:

if you know of something post up a name and idea where to find it, thanks
honestly I don't know that is getting out of my area ..............But I can tell you for sure it melts the foam completely! :shock: so I am glad I tried it on a scrap piece first :lol: :lol:
You can use mas brand epoxy resin. I have used it on styrofoam and it does not melt it. You can get it with different speed hardners. It cures smooth as glass. They have a website just google mas epoxy.
thanks I was thinking of trying the west epoxy I'll check the MAS out also. Can I spray that or does it need to be brushed on?
NO, but I tried to take off as much as I could though

it doesn't need to be permanent or anything just temporary for the construction of the mold to give it a smooth surface
I have sprayed epoxy resins with a Binks 60 gun but we had to thin it with acettone and use a pressure pot. Trouble is the acetone will melt your foam.

We made some foam molds and just used a rounded end and a square ended putty knife and troweled on auto body filler on the foam. The we sanded to form, sanded to finish, buffed and coated it with release wax and laid up right on it.

Hope this helps.

why not just take your mold and make a positive out of it with rubber or plaster of paris pull that mold out and fiberglass over the positive. Pull the fiberglass off and sand the inside smooth and you have a full fiberglass negative the exact same dimensions as the inside of your foam?

the reason for this is if you put anything in your foam mold your reducing your dimension so as long as you account for that you don't have to go through this process.
I have made fiberglass decoy and boat molds before the problem I saw with doing that is without a chopper gun it would be very hard to lay up all the detail by hand thus the idea of plaster then on to metal mold.
I could sand cast witch is what I originally was going to do then polish the casting to make a mold but was wanting to skip that step

what about spraying with a gravity gun and take out the screen , and no acetone ?
I have never used a gravity gun so I have no idea about what viscosity it will atomize. Experimentation should tell though.

Most rigs I have seen that will spray unthinned resin are hydraulic or pneumatic/hydraulic, and the guns are much more robust than the big Binks paint guns.

Takes a LOT of pressure to atomize that stuff.

Steel flex can be used w/o melting styrafoam but it can't be reduced for spraying in any way. when its rolled with a tight knapp roller it smooths out nice. good luck
I am kinda set on the idea of spraying something that way I can get into all the tight areas like cooling fins without losing detail

Thanks for all the help