Tips on Thermoplastics from Costume Craftsperson Elizabeth Flauto

by Elizabeth Flauto
Mezzo-soprano Jamie Barton (standing) with soprano Kristine Opolais in Rusalka at The Metropolitan Opera.  Costume design by Mara Blumenfeld.
Mezzo-soprano Jamie Barton (standing) with soprano Kristine Opolais in Rusalka at The Metropolitan Opera. Costume design by Mara Blumenfeld.

Today thermoplastics are more available than ever before and unlike in the past (think of Celastic and huge vacuform machines), these materials are non (or less) toxic. They are easily used without huge investments in equipment, space, or supplies. Here are four different thermoplastics useful in hand-sculpting, and some tricks and tips for their use. This list is far from extensive but can serve as in introduction to using thermoplastics as a sculptural medium.

Wonderflex • www.wonderflexworld.com
Wonderflex is, to me, the gold standard of craft thermoplastics. It consists of a translucent white plastic sheet, about 1/16” inch thick, with an embedded gauze. The gauze gives it stability and also lends the thermoplastic some of the properties of fabric (particularly the stretch properties of bias) and can provide a toothy surface that is receptive to the application of surface treatments such as gesso, Sculpt or Coat, and other paints or glues. 

It fuses to itself and to many other materials when heated; can be layered for strength or relief detail; can be reheated indefinitely to make adjustments; can be cut easily with scissors or craft knife, and can be stitched by machine with a leather needle. In single thickness, it retains flexibility after sculpting, but becomes very rigid and strong when doubled up. 

Fosshape • www.wonderflexworld.com
Fosshape, made by the same company as Wonderflex, is known as “the buckram replacement”. It is not a replacement for buckram in traditional millinery, but unlike buckram, Fosshape will not soften or collapse when wet. It comes in two thicknesses for varying uses. In its raw state, it looks like a thick felt or thin batting, but when heated the polyester fibers shrink, fuse, and stiffen. It is extremely lightweight and can be easily stitched by hand or machine before or after stiffening. It readily accepts (actually drinks) glue, gesso, Sculpt or Coat, paint, etc, and can be sized with hat sizing for extra rigidity without adding weight.

Worbla Finest Art • www.worbla.com
Worbla is similar to Wonderflex, but rather than embedded gauze, the plastic sheet contains recycled rice husks for a wood-like rigidity. It can be heated to a putty-like consistency, has a low melting temperature, and is also self-adhesive. It makes possible a high level of detail and a very smooth surface.

The Worbla company is adding new products all the time, and currently produces six versions of Worbla to explore. Finest Art (the original), Black Art (smoother & black), Mesh Art (embedded plastic mesh for strength),FlameRed Art (flame resistant), Deco Art (same plastic in pellet form), and the exciting TranspArt (crystal clear, rigid, and dyeable). 

Varaform Gauze • www.douglasandsturgess.com
Varaform Gauze, made by Douglas and Sturgess, a recent addition to a venerable product line, is more like the newer thermoplastics than original Varaform in that it’s a solid plastic sheet with an embedded gauze. However, unlike any other product, it’s paper thin. It has a very low melting temperature, allows for incredible detail, and is very smooth. It folds like fabric, fuses to itself and other materials, and can be used in combination with any of the above thermoplastics to add detail or create a smooth surface. Fused to fabric it acts like a very stiff interfacing and prevents raveling on a cut edge. Sandwiched between ribbons or fabric it creates self-supporting bows, loops, swirls, etc. and can be machine stitched. 

Tips and Tricks
The key to working with thermoplastics, obviously, is that they need to be heated to become pliable. The above products all have a low melting temp, to the point that they can be worked by hand unless heated to an almost liquid point. 

SAFETY ALERT: These products are labeled non-toxic, and they are when properly used. If overheated to the point of burning or smoking, however, they are toxic like any other plastic. Use them with ventilation to avoid any possible toxicity. A good rule of thumb is that if you can smell fumes or burning, or can see any discoloration to the plastic, it’s too hot. 

When working with any heat sources remember to use common sense, caution and prudence to not burn yourself and keep away from flammable materials. Also remember that thermoplastic materials when heated can burn skin as can the heat source. Read the directions and FAQs from the manufacturer first.

There are any number of ways to apply heat; the one you chose will be determined by the plastic you are using and the effect that you want. These include a steamer, a steam iron, a bowl of hot water, or a heat gun. Also try a miniature craft iron with various attachments and a hot knife/woodburning wand for detail. To get Fosshape to be stiff and flat, break out the steam press.

The steamer is best for blocking in large areas over a mold. The advantage of the steamer is that you can heat a large section of thermoplastic quickly, so it’s great for roughing out a shape. It gets soft enough to block, but not so hot that the thermoplastic loses its integrity, so it doesn’t stretch too much, get too thin, get tangled up in itself, or develop holes.

The dipping in hot water method has a more limited use, in that you can heat a large section evenly all at once, but the thermoplastic loses some of its adhesive property. This is great if what you want is for it to NOT stick to itself, but depending on your water temp it can get floppy and hard to handle, not to mention slippery.

The steam iron is useful particularly as applied to Fosshape, which has a felt-like texture and can be fuzzy if only steamed. I like to steam it first to block and shrink it, then go in with a steam iron and apply some elbow grease. (If you iron first, it can shrink too quickly and pucker.) With this method, you can get the surface of the Fosshape to be hard and smooth. The other best use of the steam iron is to fuse fabric flat to Wonderflex, Worbla, or Varaform Gauze. On a silicone mat on a hard surface, layer the fabric on top of, or on both sides of, the thermoplastic, and press and steam. The plastic will melt and fuse to the fabric for a permanent bond. This is great for things that are flat or flat-patterned, like a belt, gauntlets, crowns, leaves, or other decorative elements. When the plastic cools the silicone mat peels right off. 

The heat gun is best for finishing seams or joins and sculpting detail, as it’s the hottest and causes the thermoplastic to get very soft (and potentially burn, so take care.) Once you have a shape blocked in and seams put together, keep the gun moving and heat slowly while you shape, smooth, carve, and refine. You WILL need tools for this—the plastic gets too hot to handle, and skin will stick to it. I have a weird collection of tools I use for this, including wooden clay sculpting tools (perfect for grooves and details), a large tablespoon (great for smoothing and can be heated), craft knives (heating these makes them cut through plastic like butter), flat-nose pliers (for pinching together layers of hot plastic for a super flat bond), and a frozen metal water bottle (to help cool the thermoplastic rapidly if you are trying to get a tricky shape to set). You also will want to keep a tub of petroleum jelly handy, as the tools may need to be periodically lubricated so they do not stick to the plastic. (NOTE: I never use the heat gun on Fosshape, as it’s too hot and melts holes.)

Shaping and Molding
Unless working on a flat piece like a belt, you need a 3D mold over which to form the plastic. This can be as simple as a hat block, bowl, or other found object, or as complex as a cast plaster mold. For masks, unless I am making many of the same piece (more than five or so) I like to work right on clay rather than a plaster casting. Natural potters clay is the way to go for this, as it’s unaffected by heat—Plastilina itself melts in heat and releases nasty fumes. I usually start with a head block and sculpt the mask in clay. Once all adjustments are made, I cover the sculpt in aluminum foil and foil tape (available in the HVAC department of any DIY store) and smooth it down with a brayer, spoon, or clay tools. Don’t forget the petroleum jelly at this point too—you will need a release. Just massage the foil sculpt with a blob of it and wipe it off with a terry washcloth. You don’t need much, just enough to ensure the plastic will not adhere to the foil. Removing the plastic from the mold can be tricky, especially if you want to keep your sculpt intact for another round, but if you strategize, you can usually get it off with minimal patching. Once it’s free, you can patch from the inside with pieces of hot plastic.

Scroll through the gallery below to see images of Flauto’s work:

25,15,0,50,2
1,600,60,0,5000,1000,25,2000
100,100,0,50,12,25,50,2,70,12,2,50,2,0,0,5000
0,0,0,0,0,16,0,0,4,0,1,0,0,1
Clay 3D mold over head block
Clay 3D mold over head block
Clay 3D mold over head block
Completed crow mask
Completed crow mask
Completed crow mask
Thermoplastic crow mask
Thermoplastic crow mask
Thermoplastic crow mask

TIP: It’s also great to keep on hand some low-temp moldable plastic beads. I like InstaMorph. These get very soft and can be smoothed out to fill a seam; join; or patch a hole.