foam == styrofoam? And other newbie questions

[The Rock-a-who]

First, my apologies as I'm sure these questions has been asked a million times. I tried searching, but not know what key words to use, words like 'foam' and such returned too many hits.

That being said, working with foam. Is foam the same as styrofoam? Also, what's 'pink' foam I see thrown here and there in threads?

I'm probably going to start carving on styrofoam this weekend on a project. Will those styrofoam discs you see at Michaels work?

Or do you need to use a different type of foam? Also, I'm seeing conflicts that bondo will/will not eat away at styrofoam.

Is there any type of FAQ or a Dos and Don'ts for sculpting with foam/styrofoam?

Any assistance is appreciated

 

[Volpin]

"Foam" just refers to a substance thats been turned into a structure with air-trapped bubbles formed in thin walls of material. You can foam soap, glass, chocolate, really anything.

In our world, this is mostly confined to foamed plastics. Polystyrene, Urethane, latex, all of these can be "foamed" for various projects.

The styrofoam you're posting is very, very porous - the holes from the trapped air bubbles are large, and the foam is brittle. It will be difficult to shape and cannot hold small details.

"Pink" or sometimes "Blue foam" (depending on where you buy it - Home Depot sells pink, LOWES sells blue) is polystyrene foam. Denser, still somewhat brittle, but a favorite because of its accessibility, price, and ease of use.

For the dissolving issue, remember that Polyester resin (bondo, fiberglass resin) will dissolve most polystyrene foams. Urethane resin will not. It takes some getting used to in order to figure out which things can and cannot be used in conjunction with one another, but it gets easier with some experience.

 

[Wes R]

Ugh i forgot the name of the foam that the special effects students had to buy and use in art school. The stuff at lowe's reminds me of it but it wasn't as brittle I don't think. If i remember the name i'll post it or maybe someone in the industry or who took class at an art school will remember. I never got to deal with it but i know it was very messy. I think it came in big blue blocks.

 

[clonesix]

To reiterate what has already been said, there is MORE than one type of foam, and each different one has a use and cost different than the next.


To start with the 2 basic descriptions: Ridged and Flexible

Ridged is shaped into various shapes by carving and sanding or molding.

Flexible is like cushion foam, and can be bent, glued, and shaped


That was the easy part. The hard part is chemical type. Different types have different uses and cost.

The most common type is EPS (expanded poly Styrene) or "ice chest" foam. It is the little balls, expanded into a form. It can be bough cheaply, is light weight, and carves easily. The drawback is that it MELTS with any chemical solvent, even paint! That's right, if you try to paint it, it will melt like the Wicked Witch of the West when wet!

Better than EPS is Polyeurethane foam. It comes in different densities, carves, sands, nad shapes well. It is more pricey, but it is resistent to solvent, and in higher densities (6lb - 20lb) you can vacuform right over it.


For flexible foam, it can come in sheets or blocks.

Polyurethane foam is the same type used in seat cushions. It can be glued together and painted, or covered in fabric, like a muppet.

Polyethylene foam is like a camp mat. It can be glued, but doesn't hold paint well

EVA (ethylene Vinyl Acetate) is the foam in the soles of your athletic shoes, and comes in sheets of varying thickness. It glues and holds paint well. Many of the builds in the costume section use this foam. Yoga Mats, Exercise Mat, Polyethylene Foam, Yoga Mat, Exercise Mats

hope that helps

 

[The Rock-a-who]

Sounds like Polyeurethane foam is what I'm wanting (Making a Rocketeer comic rocket pack) Where do you buy this?

 

[TomSpinaDesigns]

Smooth-On, Inc. - Mold Making & Casting Materials Rubber, Plastic, Lifecasting, and More is a great source... hope that helps

Tom

 

[clonesix]

Sounds like Polyeurethane foam is what I'm wanting (Making a Rocketeer comic rocket pack) Where do you buy this?

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