Sealing Polystyrene foam?

Discussion in 'Replica Props' started by Crank729, Apr 13, 2012.

  1. Crank729

    Crank729 Sr Member

    Trophy Points:
    1,355
    I need to know of an easy way to seal polystyrene, or insulation foam. I know urethane resin works, but I don't have any on hand. Any easier ways? I have heard that acrylic paint can seal it, but I just wanna double check. The foam needs to be sealed so it can withstand a coat of bondo.

    Thanks guys.
     
    Last edited: Apr 13, 2012
  2. Palendrome

    Palendrome New Member

    Trophy Points:
    16
    I've used acrylic lacquer to seal foam--but I haven't had issues with bondo degrading the foam in the past. If your foam has a rather porous exterior than it may take several coats to seal everything. If you use foam in a mold and allowed it to self-skin then you may be able to get away with one or two coats.
     
  3. Wellss01

    Wellss01 Member

    Trophy Points:
    191
    A really great thing to use is Gesso, you can pick it up from any art store and it works GREAT for sealing foam.
     
  4. Jumpergal

    Jumpergal Member

    Trophy Points:
    180
    OOO - Gesso! What a great idea - never thought of that!
     
  5. MattMunson

    MattMunson Master Member RPF PREMIUM MEMBER

    Trophy Points:
    3,145
    Gesso is THE way to go. Not only is it cheap and easy to get, but it is perfect for the application you are describing. If you put bondo straight on pink foam, it will dissolve it.
     
  6. Kailon

    Kailon New Member

    Trophy Points:
    2
    I learned pink foam and bondo don't mix the hard way...great way to make yourself have to remake a large peice...oh well, gave me a chance to fix parts I thought was wrong...now that i think of it, its the same way I learned fiberglass resin hardener doesn't mix with foam brushed, but it has a really cool chemical reaction though lol.
     
  7. tk5378

    tk5378 Well-Known Member

    Trophy Points:
    736
    You can also wrap the foam in aluminum foil and then use bondo. Never tried it myself, but I've seen it done with pretty good success on a large scale project.
     
  8. TheBrothersRich

    TheBrothersRich New Member

    Trophy Points:
    17
    thinned down wood glue a couple coats of it that's my standard.
     
    GaryArm likes this.
  9. NormanF

    NormanF Master Member RPF PREMIUM MEMBER

    Trophy Points:
    2,516
    Or you could use urethane floral foam.
     
  10. zanefielding

    zanefielding Member

    Trophy Points:
    112
    I have been airbrushing acrylics to seal mine. You can brush on as well but I dont like streaks.
     
  11. Dogless

    Dogless New Member

    Trophy Points:
    17
    Many moons ago while I was in University, I manufactured and sold terrain for use in Wargames rto make a bit of money. I tried many different methods to seal various polystyrene foams, most have been mentioned here. I settled on one of two methods.

    1) For pieces that didn't need to have a super hard coat, I would spray a mixture of PVA and Water at around 50:50, tinted with artists acrylic paint.
    2) For harder wearing pieces, I added powdered cement to the above, which created a very tough outer shell. This needs to be brush painted, for obvious reasons. Probably not suitable for most prop work as it creates a rough surface texture, but I mention it here as someone may have some use for it.

    These days, I don's use much foam, but if I did I'd probably go with Gesso, or if I was in a hurry PVA/Acrylic paint mix through an airbrush.
     
  12. jadebmr

    jadebmr New Member

    Trophy Points:
    3
    I carved something out of this stuff and want to be able to paint it to look like a wood texture. What is the right stuff to seal it with? Not sure what kind of foam it actually is other than "floral foam". I would like it to be hard and solid.


    Thanks in advance and sorry if I should have started a new topic but it seemed like it make sense to ask here.

    foam.JPG carved.JPG
     
    Last edited: May 11, 2017
  13. cavx

    cavx Master Member RPF PREMIUM MEMBER

    Trophy Points:
    4,196
    Epoxy can apparently be applied directly to polystyrene foam (closed cell).
     
  14. jadebmr

    jadebmr New Member

    Trophy Points:
    3
    Is the floral foam a polystyrene? I guess I will test a scrap piece.
     
  15. Spyhunter2k

    Spyhunter2k Sr Member RPF PREMIUM MEMBER

    Trophy Points:
    1,625
    Old school guys designing kit car bodies used to seal plaster with latex house paint, and Bondo'ed over that. Could be used in a pinch over foam as well. My go to is epoxy resin.
     
    cavx likes this.
  16. GaryArm

    GaryArm Member

    Trophy Points:
    163
    An Old School way I have used in the past is to brush a sealing layer of wood working “PVA”. This has zero reaction on the Styrofoam, this has worked on many of the job I have done in the past. Polyester Fiberglass can be layed over it with no problem. Although as Spyhunter2k has stated, epoxy resin can be applied directly to Styrofoam, and has no reaction to the foam.

    - - - Updated - - -

    An Old School way I have used in the past is to brush a sealing layer of wood working “PVA”. This has zero reaction on the Styrofoam, this has worked on many of the job I have done in the past. Polyester Fiberglass can be layed over it with no problem. Although as Spyhunter2k has stated, epoxy resin can be applied directly to Styrofoam, and has no reaction to the foam.
     
  17. GaryArm

    GaryArm Member

    Trophy Points:
    163
    sorry guys, I am having some problem doing up loads
     

Share This Page