Instamorph is the brand name of low-temperature thermoplastic pellets which I make into sheets and then mould into my masks. It becomes soft and transparent in hot water, white and opaque as it cools, and once cool is both flexible and strong.  It can be welded to other bits of Instamorph with heat, and worked in a somewhat similar way to wax with metal tools.

It typically takes around 200gms for a human sized full-face mask (or enough for an A4 3mm sheet), and I buy the stuff in 8kg lots, most recently via Amazon.   As far as I can tell it is pretty much identical to Polymorph in the UK and Plastimak products sold in Australia; similar variations on the theme are sold under names such as Shapelock and Friendly Plastic to cosplayers and electrical hobbyists and makers of various things crafty.    All are manifestations of Polycaprolactone, or PCT.  You can also find variations inter-rolled thinly with fabric and sold for hat making and such.

If you work in vetinary or human medicine you may encounter a similar material, already made into sheets, used to make remouldable splints for animal or human injuries.   Get some and play: it’s a great material.

For maskmaking, it replaces the material Celastic, a kind of plastic which was softened in acetone and by all accounts was very nasty to use.  It replaces papier mache, which takes days-weeks to dry and doesn’t give anything like as strong or solid a result.  As well, unlike leather or papier mache, it doesn’t soften or loose shape when a performer gets it all sweaty.

It is for masks made by draping over a form, a positive (I make mine of clay), in contrast to masks made by pouring a liquid such as latex or neoprene into a negative mold.

Superheated the plastic resembles a hot glue (I use small metal tools and a spirit flame for this) and I use it to cement eyes and extras into place.   It is great material to make bits such as teeth, tusks or horns, whether part of a mask or as costume accessories on their own.

Once a mask is made, sand the surface lightly and paint with good quality acrylics, if finished with a satin or matte waterbased polyurethene this finish is perfectly durable – although it can be sanded and refinished at any time.

Tools to help with the Instamorph : 

1. A spirit lamp, sometimes called an alcohol lamp, for heating tools to work the shaped plastic form, and to ‘glue’ extras like teeth into place – your best bet for a local supplier is probably a jewellery making supplies shop.
2. A selection of clay tools – pooky sticks with soft curvey ends. And some metal tools to use with the spirit lamp, something like dental tools. And a sharpened spoon, knife and a disposable scalpel.
3. Really good industrial strength snips to cut the plastic, especially round the edges. Or, at a pinch really solid box cutter knives. But be careful, I slipped cutting some plastic and you’d be amazed how well/badly I cut myself.  It is easiest to cut when still slightly warm. You can also use a heated knife to poke a series of holes and make a cut that way.
4. Some basic silicone cookware – the things I use most are silicone cookie sheets and a flan dish (which I use to melt the instamorph in in the microwave to get a blob I can roll out), and a silicone rolling pin is an extra luxury (you can get away with a glass wine bottle, but it’s trickier). Your local budget shop will have something.
5. A hair dryer can be good if you need to soften and reshape a large area, say if a mask needs to be recurved to a different face.  Be careful of course, any thin areas (say over a nose) will heat and soften more quickly, so things can go ‘orribly wrong

Extra things I’ve learnt : 
– A silicon cookie sheet at the bottom of a large roasting dish makes an good working tray.  I usually use nearly boiling water, which is not what the manufacturers recomend, but works for me.  Also, melting in the microwave works, but don’t tell anyone I said that, as it’s probably also not recommended.
– Pingpong balls are insanely flammable!  Really don’t use a flame tool (like my handy creme brulee torch) near any ping pong eyes.
– Knives are very sharp and prone to slip.   Cutting out the rough shape when the plastic is not quite hard with the sharpest of sharp snips is the best way, then clean up with hot tools around any rough edges.  You can also heat metal tools in a flame, then sort of ‘punch out’ the eye shapes.
– Instamorph is the best glue for instamorph (I now usually melt strips of it to hold in eyes etc rather than using glue).
– Plan your eyeball style and placement early.
– Boys always want to put on girl masks.
– Accept random wrinkles as “gifts of character”

Rummage through my other masks!

mask in progress

Masks lined up for the show

The Captain