www.TK560.com

[CrazyFool]

Boy I would sure rather make forms out of foam than wood but I was afraid foam might collapse or soften (melt) under heat so I went with wood.

But these guys spray a layer of 'urethane hardcoat' over their intricate foam sculptures making them "virtually indestructible".

http://www.steltercreativewoodworks.com/STELTER1/Foam_Sculptinx.html



That sounds great to me! I wonder how this is superior from simply brushing on some resin (with hardener) that you buy at the hardware store? I wonder if you can brush resin onto foam? Will it melt the foam? Hmm. I also wonder what kind of foam would work best. Lots of questions. No answers yet. I've emailed some people and will post whatever info I get.

CF

[Culvan]

I have a co-worker who was explaining this to me. There are different kinds of resin. The ones you might buy at walmart for fiberglas use MEK to keep the hardner a liquid. MEK is a solvant that will eat through virtually any foam you can find.

There are other kinds of resin (I want to say polyurithane) that will not eat most foam.

I've been experimenting with ways of using foam for my molds. I've bought a bunch of pink foam used for house insulation and it's easy to carve into a shape. So far my best results are from using wood glue to seal it up. The foam still melts a little under the heat so it loses some detail around the corners. That's better than before though. It was bonding to my HIPS. I may try wood glue as a sealant then some sort of high temperature paint like engine enamel. I'm hoping that will give it the protection it needs.

Andy

[TK 109]

well, brushing the resin on might be easier, but will probably tend to make the form loose detail, and the brushstrokes might end up showing through the casting. i guess it depends on the application. for armor, this might no be too bad, because the level of detail isn't too high, and you may be able to lightly sand away any brushstrokes. but if you're doing something commercial, you may require a little more detail and perfection, and NO time to sand away brushstrokes....

just my take on that...
_________________
-Alex

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[CrazyFool]

Culvan & TK 109
Thank you for your input. It is much appreciated.

Here is what I learned about foams and hard shell plastic (resin) coatings over the last three days by reading and experimenting...

Pink Foam
This is sold in my area at Home Depot. It is called 'Extruded PolySTYRENE Foam Insulation' made by Owens Corning. Only EPOXY RESIN can be applied to this foam safely!! Other resins like the typical, cheap 'fiberglass resin' (which is Polyester Resin) will melt pink foam!!

Blue Foam
This is sold in my area at Lowe's Hardware. It is called 'Styrofoam Extruded Foam' made by DOW. Styrofoam is just a brand name. The blue foam is the same thing as the pink foam. They are both 'Extruded Polystyrene Foams'. Only EPOXY RESIN can be applied to this foam safely!! Other resins like the typical, cheap 'fiberglass resin' (which is Polyester Resin) will melt blue foam!!

Yellow Foam
This PolyURETHANE foam is not typically sold in hardware stores. It is a special and rather expensive foam with two parts that are mixed in the nozzle of a sprayer as the foam is sprayed onto a surface. It is not the same foam as the cheap stuff you can buy in a can at the hardware store and spray around your windows to seal cracks. (I'm not exactly sure what that stuff is.) Of the three foams I speak of here, Pink, Blue and Yellow... only this yellow foam can have the cheap polyester 'fiberglass' resin applied directly to it with no negative effects. Note: I have also seen companies online selling what appear to be large blocks of yellow or white foam. I am not positive what types of foams those are, but I'm not that concerned at the moment because lots of artists use pink and blue foam and they are readily available at local hardware stores and can be glued together into larger blocks.

Polyester Resin
Cheap crap. Commonly known as 'fiberglass resin'. It dries (if you're lucky) into a kind of unattractive amber color. Typically comes in a metal can with a small clear tube of hardener. Don't use it on Pink or Blue foam!! It will melt your foam! But if you are forced to use this resin on pink or blue foam there is one way to do it. First you need to paint the foam with a water based Latex paint. WalMart carries good stuff called 'H20 Latex' by Krylon that comes in a handy spray can. It even says on the back of the can that it can be sprayed onto foam. Spray a layer of the paint onto your foam and wait for it to dry. Then spray another coat of paint on. And then another. Don't take any chances. Make sure your pink or blue foam is completely covered with water based latex paint and that the paint is 100% dried. This will create a protective barrier against the polyester resin. Only then is it 'safe' to apply polyester resin to pink or blue foam. Polyester resin contains 'styrene' and styrene likes to melt pink and blue Extruded Polystyrene Foams.

Epoxy Resin
***Simply AWESOME*** Epoxy Resin is sold at boating supply stores. It comes in two bottles as a two part mixture. Part A is the resin and Part B is the hardener. Epoxy resin is more expensive than Polyester 'fiberglass' resin but epoxy resin is far superior in every way. If you have spent several hours laboring over a piece of artwork carved from pink or blue foam... the only resin I would put on it is EPOXY RESIN. It is super strong, dries fast, and has a beautiful crystal clear finish. It is well worth the extra money. It can be applied to all kinds of things; artwork, boats, furniture, cars, etc. My understanding is that epoxy resin came along years after polyester 'fiberglass' resin. Epoxy resin is newer and state of the art. It also has the ability to glue things together while still remaining flexible. And yes, you can apply epoxy resin to things like boats and theater set pieces in conjunction with fiberglass sheets. So polyester 'fiberglass' resin is by no means the only resin used with fiberglass. Note: some art stores carry small bottles of epoxy resin but (as it usually states on the container) they are typically only to be used for small art pieces and are not suitable for larger objects.

CF

P.S. I spent the last three days testing all of the above (except for the industrial 'yellow' foam) and I can attest that pink or blue foam covered in a few layers of epoxy resin is very strong and should make a great vacuforming form - although I have not gotten quite that far in my testing. BTW... heat makes epoxy resin even stronger!! I may, or may not spray a coat of high temp engine paint on some pink foam I bought over the weekend and coated with epoxy resin. The high temp paint was just an extra bonus because I found some that was super high temp for 'engine manifolds' at the boat store that can withstand over 1,000 degrees. Kinda cool.

P.S.S. I'm still not sure what those guys in my first post on this thread are spraying on their artwork to make it super strong. They said it's their own special mix of 'urethane hard coat' so it could be anything.

P.S.S.S. For those new to 'resin'... resin is simply a type of plastic in liquid form. It comes out of a bottle or can as a liquid, is mixed with a hardener and then applied to your surface where it hardens into a plastic. Note: hardeners have a short shelf life of something like 6 months or 1 year. If the stuff you are buying looks old, like it's been sitting on the store shelf for a long time don't buy it. The hardener might not be affective anymore and you'll end up with a gooey, sticky mess. Even if the stuff you buy looks new test a small bit on a piece of scrap to make double sure that it's still potent before you cake it onto your prized piece of artwork!

[Culvan]

Excellent information. You covered all the information my co-worker told me and more. The only thing I can add now is that all of the high temperature engine paint I tried will ate through my pink foam.

Another note on epoxy resin. You will need a scale to measure out the epoxy resin. It has to be precisely mixed or it won't fully harden. Polyester resin is very forgiving to differences in mixed ratios.

Andy

[thebluecanary]

[Culvan]

[CrazyFool]

Culvan
Thanks! I think if foam is covered with Epoxy Resin first (which is then allowed to harden 'cure') you could spray high temp engine paint on top of the epoxy resin layer with no negative effect to the foam. That is what I am planning to try soon. You are correct that you do need a good measuring cup or kitchen scale to measure out epoxy resin. I have not shared your success with polyester 'fiberglass' resin. It has given me problems even when I did everything carefully and correctly. The biggest problem I've discovered with polyester resin is that sometimes it just does not want to harden to a completely tack free (stickyless) state. Oh yeah... it also melts foam. I think I will 'stick' with epoxy resin from now on. If you haven't tried it I highly recommend it. It worked for me the very first time.




Here are a few tests I did complete on pink foam...



Here is more resin info... Tip: Wear disposable rubber gloves when applying resin. Better yet... use good, thick rubber (non-disposable) gloves. I bought a pair at Lowe's (on the shelf next to the Acetone) for $5 US. If you are planning to work with resin you should buy some of the better gloves anyway because you need them when cleaning up with Acetone. It can eat through cheap disposable rubber gloves and be absorbed directly into your skin.



CF

P.S. Culvan made a good point that even foam covered in resin and then high temp paint might still melt under a vacuforming oven. Hmm. Will have to try some tests.

[CrazyFool]

As much as I love Epoxy Resin I ran into a problem tonight. In the business sign project I'm working on I still had two forms to make; a letter 'e' and a big 19" x 24" form in the shape of the business's logo. I'm so low on energy I just could not bring myself to fashion them from wood. The logo form has lots of curves. I wanted something easier, so I began looking at foam.

Tonight I just finished a beautiful letter 'e' in pink foam and coated it with epoxy resin. While waiting for the resin to harden I put a small chunk of pink foam (that I'd previously applied epoxy resin to days ago) about 18" below one of my ovens.

The result? Areas of the pink foam chunk that were not covered by epoxy resin did not get hot. Heck, they barely even got warm. But... the areas covered with epoxy resin got very hot. So hot that they began to soften and rise. Crap!!! I thought epoxy resin was supposed to get harder and stronger under heat. Maybe that's under moderate heat, not 200+ degree heat. Hmm. Update: My conclusion here was incorrect (see next post below). The epoxy resin was fine. It was the surface of the foam near the oven (under the epoxy resin) that was warping and causing the illusion that the epoxy resin was melting.

So I tried another test. I've never used Bondo auto filler before so I caked some on a piece of pink foam. (What I'm looking for is an easy way to sculpt forms with foam and a way to strengthen the foam forms so they are not crushed by the vacuum of vacuforming.) So far the Bondo is hardening and the pink foam does not appear to be negatively affected. That's kind of strange, because on the can of Bondo is says that it contains 'Styrene' which is the same ingredient in Polyester 'Fiberglass' Resin that eats pink and blue foam.

I also sprayed a piece high temp engine paint on a chunk of pink foam that was coated days ago with epoxy resin. My thought was that maybe the high temp paint can protect the epoxy resin, while the epoxy resin gives strength to the pink foam. We'll see. Still waiting for the paint to dry. While waiting I noticed something odd. On the high temp spray can it says that it contains 'Acetone'! Great. That's the same stuff you use to clean up resin from tools and spills. In other words, it's possible that the high temp paint will eat the epoxy resin. Argh! If this test fails, the next test I will do I to put Bondo covered pink foam under an oven and see what happens. If something negative happens then I will try another piece of Bondo covered pink foam under the ovens, but a piece of Bondo covered pink foam that was then coated with a layer of high temp paint.

One of these dang test has got to work. Shoot, I could have carved the two forms out of wood by now. Oh well. At least I'm not covered with saw dust at the moment.

My conclusion so far is that epoxy resin does in fact give strength to pink and blue foam (possibly enough strength to survive the pressures of vacuforming)... but the epoxy resin itself needs to be protected somehow from the intense heat of the vacuforming oven.

CF

[thebluecanary]

Have you thought about making plaster copies of the epoxy foam? That way you keep your "good" orginal, and if you bust a mold, it was only the plaster one.

Just some ideas.

[jegner]

Interesting. Sounds like you are having some fun.

There is a product called balsa foam you might want to try. http://www.dickblick.com/zz331/11/

Also smooth-on has a product called Foam-it 8. That you can machine once it sets. It's like The can foam on steroids.

http://www.smooth-on.com/foam8.htm

I never had much luck with the insulation foam for use as a direct vac form mold material. I made a few parts from the stuff, but ended up making plaster casts of the foam mold patterns.

Jim

[TK 109]

yes, this is really cool stuff. how much does that foam stuff go for? i imagine like $30 per sheet??

this is really good stuff, keep us posted!
_________________
-Alex

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[CrazyFool]

After several more experiments I've come to the conclusion that pink (and most likely blue) extruded polystyrene foam is not a suitable candidate for vacuforming forms. Since I have no more time to experiment with foam at the moment I went ahead and made forms out of wood for the project I'm working on. I then covered the wood with epoxy resin once I determined that it was not the epoxy resin that was softening under direct heat form the oven. It was the pink foam underneath that was softening, expanding and warping.



bluecanary
That is a very interesting Idea - to plaster copies of pink sculptures. I'll have to try some experiments. Thanks!

jegner
Thanks for the tips! I will take a look at those foams you mentioned. There's that word plaster again. Hmm... I have very, very limited experience with plaster. The last time I tried mixing up a big batch (a whole bucket of powder) it hardened before I knew what happened. Maybe I'll try a really big, super duper watery batch and see what happens. Do you need to coat the foam with anything before pouring plaster over it I wonder?

TK 109
I bought an 8 ft x 2 ft x 1 1/2" thick sheet of pink foam at Home Depot for about $12. I found out that's actually a lot of material.

CF

[cod]

I've been experimenting with modeling clay and quick, down and dirty vac-copies as a way to generate forms.

Here's the basic scheme:

make your mold in modeling clay.

vac-form directly over it with a very thin thermoplastic( i used styrene).

Use the thin styrene negative form as a mold for a hydrocal positive....

I've had success with this. It may be limited to certain types of forms/detail.

I think there's room for more experimentation along these lines, and it will give you even better control of shaping and detail than foam ever could. You can even save/re-use modeling clay by having a temporary foam core to reduce costs/weight.

This is a much less toxic approach. I believe it will also be sginificantly cheaper to compare the cost of resins vs. the cost of hydrocal.


my 2 cents.

cod
_________________
<.o'>

[Culvan]

I got the idea of using pink foam from a website where they are building clone trooper armor. They coat it with spackle to protect it from the heat. I was hoping to avoid that because it creates a new surface to work. Anyhow their results are pretty good. You can check out their whole build process here:
http://www.jediokc.com/clone%20website/main.htm

Looks like they used the foam/spackle to make positive molds then vacumformed negatives then made hydrocal positives.

Thanks for doing all the experimenting on this CrazyFool. You've done a great job documenting the process here. What kind of plastic are you forming with? My attempts with HIPS wouldn't release from the plastic nearly as well as yours did.

Andy