These reviews at the bottom based on personal experience. If you have any tips you've picked up over the years, shoot me a message at firstname.lastname@example.org and I'll add it to the list!
How does it work?
Thermoplastics react to heat. The most common method of working with thermoplastic is to use a heat gun to warm up the plastic so it's soft and flexible, mould it to the desired shape and wait for it to cool. Once the plastic is set, it will harden. Don't worry about getting the shape wrong first time, you can reheat and remould the plastic. This does mean if you leave your finished armour in the car on a hot day, it will melt so do be careful!
The most common way of using thermoplastic sheets is to create a foam base and wrap the foam with worbla. It creates a more durable exterior than just plain foam. Check out Kamui Cosplay for books and video tutorials.
Equipment needed to work with thermoplastics:
- - Heat gun - to shape the thermoplastic.
- - Clay sculpting tools (or the back of a paint brush) - for sharp edges and pressing down on seams
- - Dremel - (Optional) to sand down the seams.
- - Filler/Sand paper - (Optional) but it would really help to smooth the surface out!
- - Baking paper - (Optional) but it would stop the worbla sticking to surfaces.
Tips and Tricks
It is bloody hot
Really obvious point but that stuff is hot when you heat it up. Make sure your surfaces are heat proof by using a heat proof mat or wood. For large pieces, wear gloves or keep a bowl of cold water to dip your fingers into.
Work in small sections
We all love it tight. Don't heat the whole piece in one go! Do it in small sections to get a tighter mould.
Save your scraps
You can use every last inch of thermoplastics. All you have to do is pile them up, heat the lot and roll it out with a rolling pin (or a lasagne maker) to form a sheet again. So do keep all your little scraps and not waste any!
Plan it carefully
Template and plan out what you're going to do carefully because unlike other materials, if you make it too small it would be extremely difficult to rectify.
To remove the rough texture, you can cover it in a few layers of wood glue (rather than PVA) and then wet sand and it'll be smoother than a baby's bottom.
DO NOT OVER HEAT!
Each thermoplastic will have a different melting point. As soon as you can see the plastic start to soften, you're good to go. If you heat it too much, it will start to bubble and becomes difficult to reverse.
To ensure you apply heat evenly especially on the corners by waving the heat gun back and forth and do not focus on one bit. Don't hold it too close to avoid burning.
Mould with it
Don't just limit yourself to wrapping it over foam bases. You can use it like a vacuum former minus the vacuum. An example is that I've sculpted a butt plug out of clay, slapped some worbla on it and cut the shape out. Did it 8 times then filled it with expanding foam. Now I have 8 light weight butt plugs.
A lot of tutorials recommend you sandwich the foam between two pieces of worbla. If you're cheap like me, just cut a slightly larger piece and wrap the corners onto the piece of foam and leave the back open. Who the hell is going to look inside your armour...
Comparing the different types
There are loads of different brands of thermoplastics, each with slightly different feel and properties. Thermoplastics aren't cheap so I hope these reviews could help you decide which to try and which to avoid.
Ease of Use: 7 Flexibility: 6.5 Finished Texture: 6
This is probably the most used thermoplastic in cosplay. This feels a little thicker than the other thermoplastics. It's easy enough to work with and sets quickly. Since it's thicker than the other plastics, you have to put a little more effort in to heating and shaping.
The platsic has two sides, the shiny side with the glue and the dull side. Although worbla does stick to itself, ideally you would want the glue side down. Once you have moulded your shape, you will see it finishes with a rough texture. You can either sand this or cover it in a few layers of woodglue to smooth it off. Do make sure you either press the seams in and/or give the seams a good sand after. Your armour will look terrible with worbla seams. Do be careful; if you heat it up too much and try to stretch it, it will tear and it will require a significiantly more work to smooth it back out.
Ease of Use: 7 Flexibility: 7 Finished Texture: 7.5
Significantly smoother than normal Worbla. It feels a little thinner as well so it is a little easier to work with. Still not a perfect surface but it is much better than the normal one. It will require at least a couple thick layers of woodglue to smooth it out completely. I feel it's less sticky than normal worbla but then again I might be doing it wrong. I've heard that it's harder for paint to stick to the black worbla's surface but I haven't experienced any difficulties so far.
Ease of Use: 3 Flexibility: 4 Finished Texture: 9 or 3
Extremely smooth surface and it's transparant. You can create your own custom shaped windows and shapes. It feels extremely stiff and difficult to use. It cools rapidly, so constant heat must be applied. If you apply too much heat on it, it will leave an ugly yellowish brown burn mark which looks like someone has smeared poop on that spot.
Worbla (CrystaArt) - Beads
Ease of Use: 6 Flexibility: 9 Finished Texture: 7
This is much harder to use than polymorph. It needs a heat gun and a strong ceramic bowl as it has a much higher melting point. It does however dries transparent rather than white.
Polymorph - Beads
Ease of Use: 7 Flexibility: 7 Finished Texture: 6.8
This comes in little beads. It works exactly the same way as the sheets do; you heat it up, mould it then wait for it to cool. Instead of heating it up with a heat gun, you can heat it up in a mug of boiling water. It has a work time of about 5-7 minutes before you have to re-heat it. Once it's heated up, it has a stiffer-playdoh like texture to it. Just imagine moulding playdoh but you only have about 5 minutes to work with it. I am still new to this material and my experience has limited me to only using it for gems and simple sculptures. It's difficult acheive the perfect shape if you're doing it free hand. I would recommend pressing this against a shape/mould to create a pattern. Sort of like casting but less messy.
Ease of Use: 5 Flexibility: 9999 Finished Texture: 8
This is a new plastic I've discovered. It's even smoother than black Worbla and it is extremly sticky and squishy. I can create near-seamless edges becuase I can squish the two surfaces together once the plastic is heated. I would recommend working with this a little at a time and avoid heating the whole surface all together. Once the two surfaces touch, it's impossible to peel it apart. I didn't feel like I need to apply extra woodglue to smooth the surface out.
Ease of Use: 5 Flexibility: 3 Finished Texture: 4
Ease of Use: 7 Flexibility: 7 Finished Texture: 7
Expanded PVC Board
Ease of Use: 7 Flexibility: 7 Finished Texture: 7