Sintra
Sintra (also known as Expanded PVC and rarely, PVC sheeting) is a polyvinyl chloride (PVC) plastic commonly used for signs. It comes in different size sheets and thicknesses ranging from 1-6 mm. Its forming heat starts around 150F/65C. It doesn’t conduct heat so after heat shaping it, you can pick it up and put it on your head (though depending on how long it’s boiled and the thickness, it might be hot for a few seconds). It’s lightweight and durable so if you smash it into a wall, it should survive! If you need to make something thick and resilient, minus the crazy curves and hardness, go with craft foam or wonderflex because sintra can be a labour intensive.
Building Methods and Painting
So far, we’ve found two main ways to work with sintra: layering and patterning. Layering is building the prop up from a base. Patterning involves building the shape out of poster board or paper, tracing the pieces, and assembling them like a 3D jigsaw puzzle.
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Layering For layering, no 3D model and pattern is necessary! It’s building up a flat shape or around a basic shape to make until it’s built up into the object you want. It’s the keep adding until you have nothing left to add method. Example: Lightning's sword [Final Fantasy XIII] I drew the sword out on the sintra and traced the lines for the smaller shapes I needed onto tissue paper [the gift-wrap kind], cut it out and glued the parts on.  I used craftfoam [green] to cover the edges since it’s difficult to get the sintra to match exactly and I didn’t want to cut through 3+ layers at once. But if you have time and an absurd amount of determination, you can seal it with super glue and sand it down until you have a seamless edge. A dremel speeds up smoothing the edges. |
 Patterning
| When using the patterning method, it’s usually best to start by building a 3D cardboard shape and then laying it flat so you can trace around the cardboard. This method uses a plan-ahead approach. Example: Ven’s knee armor [Kingdom Hearts: Birth By Sleep] To show the patterning process, we’ll use an example of Ven’s knee armor [from Kingdom Hearts: Birth By Sleep]. When patterning, I usually start by building a 3D cardboard and then lay it flat to easily trace around the cardboard. I’ve found it really helpful to start with a cardboard shape even if the piece is very simple.  Afterwards, cut out the shape with a box cutter. It should be fairly easy to cut through sintra, but for thicker pieces (4mm+) you may need a little elbow grease. |
 Once cut out, this is a great time to bevel the edges if necessary. It’s a little harder to bevel all the edges equally after you shape it. Use the box cutter you used before to cut the edges diagonally so the edges have a more finished look. If you’re building a 3D shape, then you can cut diagonal slits along the underside of the parts that will be sticking out the farthest. |
 Then it’s time to shape the sintra! That’s right, stick it right in boiling water! Sintra doesn't need long to cool/set. When boiling, I usually boil parts of it a little bit at a time. Once you get the water boiling, 2mm sintra takes about 5-10 seconds to get completely flexible. (It's a little longer for thicker sintra.) Although it cools in a few seconds so you have to shape it (wearing gloves or with a towel) really quickly. You can also shape it while it's in the water (with tongs or chopsticks) and take it out to make little adjustments. It takes sometime, but it's well worth the durability and stiffness. |
*Note: Be careful when working with boiling water! It’s surprisingly easy to burn yourself. **Super Important Note: If you’re boiling with a pot, use one that you don’t cook out of! Sintra leaves a thin film on any pot that you boil with so you definitely don’t want to ingest it.  After boiling and sintra, we now have a nice 3D shape for the knee armor! Then you can proceed to painting it! |
 Painting
| Most paints should work well on sintra, but acrylic paints scratch off so you’ll need to prime it with a base layer like spray paint. For added anti-scratch, use fine grained sandpaper and give the surface a quick rub down. It’ll still look smooth and give the paint pockets to sit in. If you use acrylic, make sure to seal it with a clear sealant or varnish. Example: Ven’s arm armor [Kingdom Hearts: Birth By Sleep] To make sintra look like metal, you can use metallic spray paints or a combination. To make it look more like metal and warn, spray the piece with a glossy or matte spray paint. Then coat it lightly with an acrylic colour you want and wipe it off with a paper towel to create some depth. As an example, this photo shows how Ven’s arm armor looks at the beginning steps.  Then mix the final colour/shade you want the piece to be using metallic acrylic paints and dip a dry paper towel into the mix. Wipe almost all of the paint off so there is only a little on the towel and buff the piece using circular motions. Then buff it lightly with black, but do it in a straight line instead of a circle and seal! As we can see, Ven’s armor a lot more like more like battle worn armor now.
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Mess up!…err….Experiment. That’s how we’ve come up with all of our painting techniques. |
Heat Forming Techniques
Heat Forming
Heat forming starts around 150F/65C and at 212F/100C it has the flexibility/consistency of poster board (though it also depends on thickness).
Boiling
The easiest way to heat form sintra. Throw it in a pot of boiling water, pull it out and shape it however. Tongs are good for handling sintra in the boiling water, but we’ve found cooking chopsticks offer the most mobility and grasping power. Also to avoid burning your hands off, gardening gloves work well. With the leather ones you can put your fingers in the steam and water for a few seconds before burning! You can reshape it with it fully painted and in our experience so far, the paint has stayed on fully in tact. We can’t stress this enough - If you’re boiling with a pot, use one that you don’t cook out of! Sintra leaves a thin film on any pot that you boil with so you definitely don’t want to be ingesting it.
Heat Gun
Heat guns start in the 200+ degree range and go up from there. Heat guns are convenient for sintra pieces that are way too big to throw in pot of water. If you need to combine two pieces of sintra together so they’re flawless, the heat gun will be you’re best friend. It’s fairly hard to make two glued pieces of sintra look seamless, but the heat gun will literally melt the edges.
Ridiculously hot blow dryers
They work on 1-2 mm, but it’s really hard to shape the sintra because the blow dryers aren’t hot enough.
Other ridiculously hot tools (like hair straighteners)
You can use a hair straigthener for small details that you want to bend slightly and not have to reshape completely with boiling. Even though it works well, you’ll need to be really careful with this method. You may easily ruin your hair straightener if you touch the sintra with the hot plate (besides the fact that it smells like burning plastic), but if your hair straightener gets hot enough then you can hold it right over the sintra without touching it.
Patterning & Finishing
Shaping
For difficult bends and shapes, score the back and cut out a small wedge where you want it to bend.
Cutting
1-3 mm: Easily cut with a box cutter
4-6 mm: Use brute force or score and snap it (and brake your hands in the process); you can also use a circular saw if it’s legal where you’re staying.
Dremel
A dremel is a rotary tool for sanding, cutting, etc. It speeds up sanding, but it’s easy to mess up and can dent the sintra so I use it mostly for smoothing edges. It also makes a mess and it takes days to clean up all the plastic dust so do it outside. Safety goggles and a breathing mask are good ideas. As for cutting sintra, I’ve found it to be quite useless, but that might only be because I have a cheap one. When you sand hot glue, the friction melts the glue and sintra into a gooey mixture you can smooth out (be careful cause it could be hot, it depends on what speed setting you dremel is on).
Glues
Superglue
Other than getting everywhere, super glue is effective, but we’ve used it more for creating a seamless edge than holding pieces together. Seal the edge of where to pieces meet and then sand it down with fine grain sandpaper.
Hot glue
It holds well, and when it hits the sintra, if it’s hot enough, it will give off fumes so don’t breathe too much of it in. We have put superglue on hot glue while it was drying before for added hold. From what I remember, it made the superglue fumes worse.
E6000
This is an amazing glue that holds anything together, although we haven’t personally tried it on sintra. In theory it should work pretty well though.
Other Materials
Craft Foam/Wonderflex Wonderflex is a woven twill plastic that is far more malleable and thinner than sintra. It’s softens around 150F/65C and you can heat mould it to objects with details. If you can make it out of craft foam or wonderflex, do it. For the masochistic, there is sintra.
Paperclay
Paperclay is an air-drying modelling clay that is very useful when creating small shapes or details on sintra. While the material itself is very easy to shape, it tends to crack without a hard sealant. You can shape paperclay directly onto sintra and let it completely dry. It will usually dry completely overnight. Then cover the shape with several layers of gesso (with time to dry in between). This will ensure that your prop has a very durable shape that won’t crack or fall off.
More Info
Working With Sintra
A brilliant tutorial with lots of info on the bearing capacity of different adhesives/fasteners, painting, and more.
Shopping
You can go to local sign shops and beg some sintra out of them, but there is no guarantee what colour, thickness, or how big the pieces are, but free stuff is free stuff. Other than that, U.S. Plastic carries it, and from our experience, they are reliable.
US Plastics
Look for sintra under the name "Expanded PVC". It comes in many different colors and thicknesses.
All cosplays and props belong to Dark and Ven of Deep Dive Cosplay, and the layout was designed by Dark. The original term "Deep Dive" belongs to Square. All original characters, character designs, and other concepts belong to their respectful owners.