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Topic: Making props out of sheet foam
Message: Posted by: George Ledo (Sep 19, 2006 06:44PM)
I donít know how many of you have an occasion to make props out of sheet foam. However, over the past couple of weeks Iíve been making some foam props for a show, and, while it was on my mind, I decided to expand the section on foam in a book Iíve been working on for a couple of years. The book has nothing to do with magic: itís about how to design and outfit a haunted house using professional theater and movie techniques on a household budget. Below is a slightly revised draft of the section on foam, and, at the end, are photos of one of the pieces I made.



A discussion of sheet foams and their applications in the entertainment industry could take up an entire book. However, in this section Iíll summarize some of the main points, focusing on three types of foam that can be used to make props for a haunted house. These are Styrofoam, EPS, and foam rubber.

Although the word ďstyrofoamĒ has just about become a generic term for any rigid foam product, it is actually a registered trademark of the Dow Chemical Company, and applies only to the blue sheet foam insulation made by them. Styrofoam is available at home-improvement centers and is good for lightweight items that wonít see much handling, such as tombstones or display coffins. The material usually comes in 2x8 foot sheets, and in various thicknesses.

White rigid foam, known as EPS or expanded polystyrene, is available in sheets as well as large blocks, and can be used for a lot of the same purposes as Styrofoam. This is the material used in coffee cups and other white insulated containers, but it is also used quite often in the architectural, display, and theme-park industries for specialized moldings and details. Covered with a special hard coat product, it is quite durable and can easily pass for real stone, cement, and other materials.

It is interesting that both of these products are the same basic material (polystyrene), but that Styrofoam is extruded during the manufacturing process, while EPS is made by an expansion process. This is what gives them different surface textures and characteristics. A search through the Web will provide lots of information on these products and their differences.

Please note that that these materials are flammable and can produce toxic fumes: make sure to read the warnings printed right on the product, or on the Material Safety Data Sheets available at the store or through the manufacturer.

Because of its light weight, sheet foam is very easy to use. It cuts beautifully with a serrated kitchen knife or small handsaw. An electric band saw is even better, but a jigsaw tends to chew up the edges due to the up-and-down motion of the blade. It is also often cut with a hot-wire or hot-knife cutter to create very complex moldings and extrusions, although this process creates toxic fumes and needs to be done with a respirator and proper ventilation.

Contrary to logical reasoning, sheet foams can also be turned on a lathe. Youíll need to glue a piece of scrap wood securely to each end of the foam blank for the lathe to grab onto, then use a very sharp turning knife and a very gentle touch. The downside is that it makes a mess all around the lathe, so youíll need to clean up often. Iíve made a fluted Greek column from foam, as well as several large candlesticks.

If you make a mistake while carving, you can use a product named Great Stuff, which I like to call the foam carverís Undo button. Itís a spray insulation that expands once it hits the air and hardens about an hour later. Once hard, you can cut it or carve it just like sheet foam.

Foam pieces can be adhered together with plain old white glue and pressure for a few hours, although this works better with Styrofoam than with EPS because of the surface texture. Also, the 3M Company has a product named Spray 77, which is somewhat like a spray rubber cement and works very well on EPS as long as both surfaces to be glued are very smooth.

Very large or complex pieces can be made or carved in sections and glued together. You can also use glued dowels to reinforce the joints, although youíll want to pre-drill the holes to avoid internal stress and tear-out. I also like to sharpen the ends of the dowels slightly to make inserting them easier.

Once your prop is finished, youíll want to protect the finish from dents and scratches, and there are several ways to do this. The traditional theatrical way is to cover the prop with cheesecloth using slightly watered down white glue. This will provide a nice hard finish, and you can always apply a second coat if needed. One problem with this technique is that the texture of the cheesecloth tends to read through the final finish, but this can be prevented by applying a thin coat of lightweight wall joint compound before painting the piece.

Another way to protect the prop is with a product called "Sculpt or Coat," made by Sculptural Arts Coating, Inc. This is a water-soluble product that provides a very hard surface on foam, although for some applications youíll want two or more coats. It comes in several sizes and is very easy to use: just brush it on. Of course, if your prop will never be handled, you can just paint it.

One important consideration is that a number of finish products, including spray paints, will melt foam, leaving a surface that looks like nothing else on earth ó except melted foam. Youíll need to use a water-based (latex) paint, or, if you really want to use spray paints, coat the foam completely with a water-based product first, and then use the spray paint on top.

At the time of this writing, Krylon has come out with a water-based spray paint. I havenít used this product yet, so I canít comment on it.

The third type of foam, foam rubber, is available at fabric and upholstery shops, and is very good for making lots of things besides cushions. It can be used to form a body, it can be wrapped around a pole and tied with string to make ďturnedĒ table legs or thick candlesticks, it can be used to carve faces, and is often used to make faux rocks for theater and the movies. Plain white glue holds it together well, and, in contrast to sheet foam, it can be spray-painted although of course the surface texture will show. Foam rubber is one of those products where we definitely donít want to take anything for granted.


Below are two photos of an EPS cross I made recently for the graveyard scene in [i]The Sound of Music[/i]. Since my sculptural skills leave a lot to be desired, I wasnít going to try to carve the thing in one piece. So, I made it out of seven separate pieces, glued and doweled together and covered in cheesecloth, Sculpt or Coat, and texture paint. The cross itself is just over two feet high, and the base is wood. On its casters, the piece is six feet high.
Message: Posted by: George Ledo (Sep 20, 2006 04:18PM)
Sorry... here are the photos:

[img]http://img96.imageshack.us/img96/1605/cross1tp8.jpg[/img] [img]http://img96.imageshack.us/img96/9118/cross2ac0.jpg[/img]