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"How do you harden styrofoam?" Topic

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11,388 hits since 8 Mar 2009
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GoodBye Inactive Member08 Mar 2009 10:11 a.m. PST

I'm building an early 20th century Russian Torpedo boat for a series of 28mm games set in the Black Sea. They'll be called "Lt Kiji's Excellent Adventures", I anticipate the campaign starting just prior to WWI and going thru the Russian Revolution. I have ordered my ships fittings and guns from Revirsco and I have the soldier/sailor castings I need a mix of Brigade Games and Copplestone. I've carved a 4" x 30" hull for the torpedo boat out of styrofoam and it looks good. In fact I'm ready to start assembling the model and painting the figures.

The styrofoam is prone to dings, breaks and bends unfortunately. I'd like to harden the outside of the styrofoam with something that I can work (sand) with after it drys and hardens. I've used the liquid plastic that RR's use for terrain, but it doesn't dry hard enough to smooth effectively.

So any ideas from anyone regarding a material that won't attack the styrofoam and will dry sufficiently hard to protect the model and survive smoothing with a fine grit sandpaper?

thanks in advance,

Grinning Norm Inactive Member08 Mar 2009 10:17 a.m. PST

Don't know if styrofoam is the material of choice there. I would probably use the 'pink foam' or so which is much denser than styrofoam.

Or finish the model and coat it with pva but you won't really be able to sand it then.

GoodBye Inactive Member08 Mar 2009 10:20 a.m. PST

That's actually one of my concerns GN, I may have picked poorly regarding my base material. This first hull really turned out well though.

aecurtis Fezian Inactive Member08 Mar 2009 10:28 a.m. PST

Try this stuff, which is made expressly for that purpose:


And as always, test it on a separate test piece just to make sure it does not react adversely with the foam you're using. Even though it shouldn't, better safe than sorry.


GoodBye Inactive Member08 Mar 2009 10:37 a.m. PST

Thanks Allen, that's exactly the sort of thing I was looking for. I'll be ordering some today.


Richard1967 Inactive Member08 Mar 2009 11:45 a.m. PST

I used to make a lot of buildings for my 28mm GW Fantasy minis using styrofoam(the white kind used for packing TV's and such).I used Wood Glue(like Elmers Glue but a bit stronger)to harden the styrofoam,just spread it on liberaly using a paint brush and it also would hold the paint better(paint would stay on the surface,not sink into the pores of the styrofoam). My buildings would get knocked of the table occasionally, but the combination of the glue and the paint would protect it from most breaks and dings

ming31 Inactive Member08 Mar 2009 12:37 p.m. PST

In the UAS try to coat it with Durhams water putty .

TeutonicTexan Inactive Member08 Mar 2009 1:52 p.m. PST

A while back someone posted a foam hardening method while discussing making terrain boards using the normal expanded styrofoam. They stated that after they shaped the foam, they painted a polyeurethane type wood varnish onto the foam which soaked into the spaces between the foam "balls" and hardened creating a honeycomb of varnish. The foam was as hard as a rock afterwards. You might be able to use the varnish, then apply any texture you need on top and shape as needed.

thehawk08 Mar 2009 3:46 p.m. PST

There are modelling grades of the blue foamboard.
SM is the construction grade.
There are 2 denser grades – used for building 3d prototypes.
As used to make 1:1 scale car prototypes.

CeruLucifus08 Mar 2009 8:19 p.m. PST

I believe this is the web site of the originators of Foam Coat and related products; click on their link for "Foam, Glue & Coating System". They appear also to have an additional product, Boost, which goes on top of Foam Coat and makes it "bulletproof".

Hot Wire Foam Factory web site:

(I haven't used any of this stuff myself.)

ex TMP reader Inactive Member09 Mar 2009 4:40 a.m. PST

What is blue foam? This always seem to confuse people so Jed made up a page specifically to explain what it is and is not as there is so much disinformation out about it.

please see the below link for an explanation of what styrofoam is and is not, also has pictures..


Honcho Inactive Member09 Mar 2009 6:43 a.m. PST

Acrylic primer would seem to work. The kind you get in a big bottle at art supply places.

Personal logo J Womack 94 Supporting Member of TMP09 Mar 2009 11:07 a.m. PST

Dip it in concrete?

GoodBye Inactive Member09 Mar 2009 11:10 a.m. PST

Thanks all, some really great ideas here. I think I'm going to try the material that Allen and Don Rice suggested. I'll let everyone know how it works.


PapaSync09 Mar 2009 11:59 a.m. PST

Model airplane enthusiast build many of types of R/C place using foam. Ive read about many different techniques that they use to cover/strengthen the foam wings and bodies. I've seen them uses fiberglass cloth and coating it with CY. And for extra strengthen the may lay down strips of carbon fiber tape. Check out a few Model airplane sites.

link link


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