Set Sculpture terminology (EPS Foam Carving)

Another terminology page devoted this time to set sculpture, currently used in film and TV series in North America.  

 Night at the Museum II:  Styrofoam moon craters and rocks

 Eight Below: Styrofoam landscape

Conceptual design: From the art dept which is approved by the Art director or Production designer (You hope) is then handed off to the sculpting lead.
Who decides the best approach of how to execute the design… sometimes its fiberglass, or a clay item which is molded but the most common material for set sculptors in North America is Styrofoam also known as (EPS) Expanded polystyrene.  Styrofoam comes in different grade or density. Ask your dealer what’s best suited for your purpose. I have found that the denser the foam, the easier to carve and sand. The lighter cheaper foam can become difficult to tool.  It is however more expensive than the lightweight.  The UK and New Zealand have strict laws against using Styrofoam and fabricate much of their set parts in Plaster from my knowledge of those who I know work there.
For this post we’ll say Styrofoam is the material best suited for the job. This comes in handy for very large, light weight set pieces or oversized props.
Depending where you are located we buy Styrofoam in Billets measuring 4’x4’x16’ typically at this size you need a huge space. It is possible to get 8’ lengths.
In some cases if all you can find is Styrofoam sheets at lumber yards or a Home Depot will carry such items in different thickness but only somewhere in the 3’-4’ range.
This big billet size is ideal for carving statues, columns, capitals, or anything of bulk. A nice advantage is that Styrofoam can later be hollowed out to decrease its weight; a pre-determined cut out section then can be glue back on.

The next step is sizing up the best way to economize your billet of foam for.
Hot Wire Cutting:  This is a system used in which a
Nichrome wire  is connected to a custom made or bought handles, a bow, or a hot wire table rig with a switch connected to a wire and a plug. Check out YouTube for an example of hot wire home made tools or search the internet to get some ideas. Custom made are more economical if you’re doing small projects. We will get into building hot wire tool on another post for now lets stick to terminology.

Hot wire table connector

Nichrome wire: There are two readily available types of wire,   Nichrome A which contains 80% Nickel and 20% Chromium and Nichrome C contains 60% Nickel, 16% Chromium, & 24% Iron.

The only real difference is Nichrome A has higher tensile strength and a higher melting point. Where Nichrome C has a little higher resistance per foot and increases more resistance per foot as temperature increases.

Both come in gauges ranging from 10-40. The smaller the gauge, the larger the diameter. 10 gauge = 0.102 inch diameter, 40 gauge = 0.0031 inch diameter. I tend to use a higher gauge myself; everyone is different on preference though.

The more wire length you have the more resistance it creates, therefore requiring an increase on the variac dial. It’s best to test your wire heat by starting from zero and increasing the dial on the variac till it cuts through your Styrofoam piece with ease.

In many cases you can let the wire get close to red then dial it back. Test for your self to adjust accordingly. Go slow to start as the wire can heat up incredibly fast.

This plug is inserted into a Variac voltage regulator rated at 110v input with an output voltage of 0-130V.  Maximum output current is 20A with a capacity (KVA) of 2.0. The front of the unit has two receptacles, a voltage meter, fuse and on/off switch. Some have currents of 15A. 20A are best. This is a heavy item at approx 24lbs.

 Variac voltage regulator

The variac gauges the heat level and allows the wire to heat up creating a Hot wire cutting system.  Safety risks include sever burns from the heated wire, DO not touch to see if it’s hot. Yes sounds stupid but I’ve seen someone do it….DOH!
Always  turn the heat level down before plugging into the variac otherwise your wire becomes flash paper and will glow orange and burn up before your eyes….seen it done, mistakes do happen.
WARNING:  Always Refer to building instruction through this blog or other experts, don’t try this at home without the proper advice. Wear a well fitting Respirator with HEPA, N100, P100 or R100 cartridges whenever hot wire cutting. I use 3M and North masks. Replace the cartridges when either you haven’t used them in a while or the smell is evident from excessive use. To keep your cartridge from being used up too soon store in either a well sealed zip log freezer bag of a plastic bucket with a sealable lid. This delays the cartridge from continuously working when exposed to the environment. Ask you local safety supply company about recommended respirators.  The fumes given off from hot wire cutting contain CARCINOGENS  and are extremely bad for your health. This can cause headaches, sore eyes and throat. If Possible do any cutting outside or a well ventilated area, or if you have access to a paint booth with extraction fans.

Templates: can be cut from1/4”banana board from a hand drawn or enlarging projector that is traced onto the board then cut out with a jig saw to get your out shape. Two of the same are required as the hot wire runs along this on each side of your billet cutting out the shape. This saves excessive time in blocking out your piece, getting the overall basic shapes. It’s recommended to run a strip of aluminum foil tape along the cutting edges of your template as the hot wire if stopped can burn into your board…I also like to drill random spaced holes in the template and use Duplex nails AKA double head nails to hold it to your billet of foam. Note: do not positions your nails where the hot wire can hit it...It will not cut a nail!
The Hot wire system is ideal for quick sculpting with less mess. But eventually you’re going to have to Carve the foam

Maintaining and Cleaning your mess which is inevitable with any Styrofoam projects. The foam beads, when carving, scraping, and sanding gets everywhere. Tape a roll of polythene plastic sheeting to the walls and floor to make a containing room. A painters plastic sheeting drop cloth will do too. Surrounding your area is best for maintaining the mess.

I suggest wearing at least a dust mask when carving, safety goggles also to keep dust out of your eyes. The fine particular dust can enter your lungs and create a dry sore throat over extended work. Styrofoam can also get into your eyes and become irritable. Usually you can flush with water to get out. Goggles will only make your life easier. For clean up fill a sprits bottle with water and on a fine mist occasionally spray the floor, not too much. When cleaning up at the end of the day a sweeping floor compound is ideal Dustbane is widely used. Also a shop vaccuum is best or an air compressor for containing the mess with an adjustable pressure nozzle, set on low; this allows you to blow the foam off walls. When cleaning safety regulation state: The nozzle pressure must remain below 10 psi (69 or 70 kPa) and personal protection equipment (PPE) must be worn to protect the worker's body, especially the eyes, against particles and dust under pressure. For simple cleaning, wear goggles so dust doesn’t get in your eyes.
In many Professional shops workers use air hoses to clean off their clothes and faces I am not going to recommend this due to:

WARNING: compressed air itself can be a serious hazard. On rare occasions, some of the compressed air can enter the blood stream through a break in the skin or through a body opening. An air bubble in the blood stream is known medically as an embolism, a dangerous medical condition in which a blood vessel is blocked, in this case, by an air bubble. An embolism of an artery can cause coma, paralysis or death depending upon its size, duration and location. While air embolisms are usually associated with incorrect diving procedures, they are possible with compressed air due to high pressures. While this seems improbable, the consequences of even a small quantity of air or other gas in the blood can quickly be fatal.
Understand that this is an extreme case, but I have to put out this warning.

Another approach to shaping foam other than hot wire which is the most commonly used is to cut with an Electric chain saw. This can be found in hardware stores or in some cases rented. Don’t used gas too awkward to fire it up over and over again as you will be cutting the foam then placing it down repeatedly. This is a quick effective way to block out your shape but this is three times the mess of a hot wire. It can also be used after you’ve hot wired to better define your shape.

You can get even more refined with a Spiral curry comb. This is a tool used to brush horses with its ideal for shaping foam. Highly used and in every set sculptor kit. They are hard to find due to curry combs changing but a horse grooming or some pet supply companies still carry them. It is best to get the smaller version with no more that five rings. These rings will eventually break during usage so buy a couple of them they are cheap.

Carving knives: Again another personal preference here. Most sculptor use a fish fillet knife with a long thin blade. Some like an Olfa HB knife with replaceable blades.
And many like to find unique knives or custom built that best suit them. I like a good fillet knife and a Olfa HB knife, plus a smaller fruit carving knife set for fine detail.
Olfa carries a variety of knife sizes but HB is the most highly used in the industry.

Maintaining sharpness is key to a good carving. Carving stones of in some cases a hand held sharpener helps.

A  Hilti- foam gun with replicable canisters are the best result for gluing foam pieces together. After applying push pieces together to squish the glue down (the flatter the glue the tighter the bond as this foam expands which you wan to prevent).  Pull the pieces apart and sprits with water to accelerate the drying time. Let the Hilti-foam get just past tacky to the touch…don’t use your hand to test. Do a small test first for a feeling of timing. Hilti-foam is impossible to get off that easy and can take many hours in a shower or the eventual sweat from your hands so therefore wear surgical gloves. Best way to get Hilti-foam off is to wear a pair of gloves for many hours allowing your sweat to penetrate through the foam making it lose. Several hand cleanings may be required.
Don’t panic it’s common. Hilti-foam will not come off clothes either. Nasty,  but the most effective gluing system.

When you’ve sculpted you piece to the dimensions required fine detail or smoothing out is achieved best with Drywall sanding sheets  sometimes sandpaper at 80 grit. Eventually leading to Sandpaper at 100, 120, 200 grit.  Depending on your foam selection will determine how to sand it. Some foam is denser and easier to sand.
Test it out on a spare piece first as certain foam grades tend to tear when sanded. If possible use a better grade, denser for best results.

Now that you have your part finished you can coat it in many different ways. The most common used in film is to the polyurethane spray coat system. These are usually companies that have an expensive spray system using 55gl barrels of material

Demand  products carries systems for hard coating. These are expensive. Another way is to buy your own urethane two part mixing kits like Smooth Cast 300 for a smaller application from Smooth –on. This can be brushed on foam as a coating. Foam coat from Rosco.  Google foam coat, to track down a supplier. Many filling and sanding layers are required. Hard coat spray systems leave an orange peel look which then needs filler to get smooth.

This might also be too expensive. The cheapest way is to water down carpenters glue. This glue can be purchased in 1-5gallons. All depends on your project.
Never spray your Styrofoam with aerosol paints or primers. Acrylic or latex paints through a spray gun are fine. ALMOST any organic solvent (not alcohols) dissolves polystyrene!
Acetone can be used to create a melted set affect. WARNING: if you attempt this us a respirator in a well ventilated area or outside as mentioned above.
So there is a lengthy terminology of set sculpting. I can’t cover everything in this but hope to break some down in future posts.

 Night at the Museum II

 Smallville

 Final Destination 3

 Muppets Wizard of Oz

Edison & Leo miniature landscape piece.

 Night at the Museum II: 1/4 column pieces cut from a template and ready for gluing


EPS Styrofoam is commonly used in movie sets pieces like statues and massive columns, amusement park sculptures. I found it to be ideal for miniature landscapes and over sized props. Good luck and remember to follow the safety steps.