urethane foam replacement

I am a student and my school just decided to ban urethane foam from our campus. I am hoping to find a less toxic substitute with similar properties. Blue and pink foam lack the density needed for detail work. Does anyone have an idea of what I should use and where to source the product?

CNC Rhen… its harder but you get to play with he CNC machine. Clay is softer… and can be hardened as handling can warp your design.

MDF glued into big blocks works well, although you will need some power tools to cut and shape it. It will give your model a realistic heft to it as well. And, you can get it for cheap and sometimes free!

I second laminating mdf if you can’t get your hands on ren.

fiberglass resin works good with rhen and MDF too. How do you spell REN or RHEN?

mdf has formeldahyde, bad to breathe when cutting/shaping. its renshape, freemansupply.com has it. get the 10-20lb density for easy of shaping. if yur safe, i dont see the problem with foam - just dont re-shape it.

you spell it RENSHAPE… you can get it from Freeman Supply at:


They make a bunch of different densities, and it is all polyurethane. which is, of course “urethane”.

Guess you’re taking a step back to the old days with Chevant styling clay.
also available from Freeman Supply. It comes in “billets”; a 5-6" diameter log about 16" long… it’s a pain in the arse to work with unless you have the necessary equipment.


When you say they have banned “urethane” what do they mean? And, were I you, I’d question why the material is banned. Ask your design, or lab instructor for a clarification; it should be as important to him as it is to you. As is typical, some numbnutz desk jockey probably used a sweeping generalization to ban “urethane” from your campus based on an incomplete understanding of the material.

Many, if not all, materials are of varying degrees of hazard based on the whether they are liquid, gas, or solid. So, are they talking about urethane resin (liquid form), urethane foam (solid form), there is no gaseous form of urethane, per se, until it is burnt, at which point it is no longer “urethane”; it becomes a component of its combustion; carbon monoxide, carbon particulate, cyanide, etc.

All of the specifics mentioned above are to be found it what is known as an MSDS; Material Safety Data Sheet. You should learn how to read an MSDS, it contains all of the information you need to protect yourself while using materials, be they polyester resin, epoxy, wood, “urethane”, or whatever.

This is the MSDS for RENSHAPE 440 Styling Board:

Here’s a brief from the MSDS

Trade Name: RenShape 440: Intended Use or Product Type: Low Density Modeling Stock.
OSHA Hazardous Ingredients: The components of this product are not considered to be hazardous as defined by the OSHA
Hazard Communication Standard (CFR 1910.1200).

Flash Point: Not Applicable
Fire Fighting Extinguishing Media: Carbon dioxide, dry chemical, foam, water.
Fire Fighting Equipment: Use self-contained breathing apparatus.
Fire and Explosion Hazards: Decomposition and combustion products may be toxic.

Skin Protection: Wear canvas gloves as a standard handling procedure.
Respiratory Protection: Use NIOSH approved dust mask, if required during machining.
Eye Protection: Wear safety glasses to protect against dust particles during machining.
Engineering Controls: General mechanical and local exhaust in accordance with ACGIH recommendations.

Conditions to Avoid: Excessive heat for prolonged periods of time.
Stability: Stable.
Incompatibility: Strong oxidizers, acids and bases.
Hazardous Decomposition Products: Combustion may form toxic materials. Carbon monoxide, carbon dioxide, benzene, oxides
of nitrogen, hydrogen cyanide.
Hazardous Polymerization: Will not occur

If your campus is going to ban urethanes, I would suggest that they also ban WOOD:

Check out the MSDS for Wood Dust

Notably for both urethane and wood, dust is the predominant threat; Inhalation being the first path of ingress into the human body, followed by Skin Contact, Ingestion, and Injection (hydraulic fluid, spray paint, etc.) The solution; wear a respirator while sanding and grinding either material.

The hazards to firefighters and occupants, attributed to polyurethane found in RENSHAPE, would be minuscule compared to the components found in the materials that the building itself is constructed of.

One solution, albeit an unacceptable one, is the old adage; It is much easier to beg for forgiveness, than it is to ask for permission.

Buy the RENSHAPE, and lie… … . .

If the campus has banned PU based foams can you work around this by working at home or outside of the studio? We frequently used blue foam in our shops and while not the best, if you are not protected accordingly (face masks while sanding), it’s actually pretty safe i believe as long as you don’t melt it or use any toners that eat it and produce noxious gases.

I actually did most of my work in a residence study lounge, and the place was covered in blue foam dust after a few nights of (continuous) work. Always fun to be sanding away on a model at 3am when the drunk liberal arts students come stumbling in and looking at you with a complete “WTF” expression in seeing the entire room, myself and half the hallway covered in blue dust… :slight_smile:


drunk liberal arts students come stumbling in

whoa… … … that would have been me. :open_mouth: We used to sneak our Schlitz Malt liquor into the dorm in typewriter cases.:sunglasses: Purdue’s ID program, at the time, was in the college of Liberal Arts… . … . go figger.

type’writer n. machine with keys for producing printlike characters one at a time on paper inserted around a roller

It’s strange that they would ban PU foam. Polystyrene (blue foam) IS biotoxic, while PU is chemically inert. PU dust is dangerous as is ANY dust – the mechanical effects of the dust are a problem, but can be guarded against by using a repirator. The other reason to ban PU is that it causes corrosion on steel – but I would think they would just ban it on machinery.

Balsa foam, thought it looks like PU foam in it’s denser forms is actually phenolic, so maybe you get away with that.