Working With Sintra To Make Armor

Okay, loads of people want to make costumes with armored pieces, but how many of them actually want to buoild armor with fiber glass? I mean are you kidding? Do you KNOW how long that takes, how many steps there are? If you had forever, a hefty budget, and a deathwish, you could do it, but really why bother? (I’m exaggerating, of course)

So try doing it with Sintra. Sintra is a thin plastic sheeting material that becomes flexible with heat. There are comparable products, like Wonderflex, which is about twice as expensive for half as much, but it can be worked in the microwave, hot water, or even with a hair dryer. I’ve been told it’s easier to work with than Sintra, but, and this is a big but, if it melts in hot water or under a hair dryer, how on earth will it hold up? So I went with Sintra, which has a higher melting temp, and can be easily painted, built up, reinforced, etc.

Where to find it:

Now if you’ve done research and are finding this blog post while looking for shopping sites or whatnot, you have come to the right place!  I was doing tons of research to find where I could get this shit, and found ONE single solitary forum mention of where I might be able to find it, and it turned out to be a goldmine, so I’m spreading the word. If you want to find Sintra cheaply, then call your local sign shop. Mine sold me a 4×8 ft sheet for $40, roughly twice the size of what I needed, so I had pleantly of extra! Sintra comes in many thicknesses, but the thickness they will most likely sell you is 1/8″ thick. You’re saying, “crap that’s thin” but it’s also hard and trust me, durable. It is pale white in color, and sort of resembles poster or foam core board.

How to make a pattern and cut:

Now this is very important, and I cannot stress it enough. You’re going to need two tools, a razor blade or box cutter, and a pair of sturdy sheers, like crafting sheeps or tin snips or whatever. This stuff isn’t hard to cut through, but it shatters, so you’ll need the razor blade to score (I’ll explain more later)

To make a pattern, DO NOT USE FABRIC. The reason is simple: fabric is too flexible and the sintra WILL NOT obey the same flexing rules. Use sturdy paper or poster material and you’ll get a good idea of how the Sintra will flex when heated. That is not to say that if you have a smooth curve, the Sintra won’t fit it, but you should not anticipate that the Sintra will sculpt like clay or stretch like velour.

cut out the pattern and trace it onto the sheet of Sintra. One Both sides!!!!! Why? Because you need to score the lines on both sides, following the pattern line with the razor blade. Why? Because the outer covering of the Sintra will shatter when you cut it, unless you give the force a “give point”. When you cut into it with the sheers, it will shatter until it reaches the scoring point, so CUT OUT THE SHAPE JUST OUTSIDE OF YOUR SCORING LINE. If you need to later on, you can shave the edges with the razor blade to get a perfect, smooth edge. Use sand paper for smooth edges (I combined carving with sand paper to get a perfectly rounded edge)

To heat and flex Sintra:

I found a great youtube tutorial showing this process, though I would have edited it a bit (no offense, it’s just too long and not detailed enough)

Preheat your oven to 250-275 F Put the piece of Sintra in. It should only be a few minutes before the Sintra turns soft, like a big floppy piece of thick dough (it isn’t thick, but it behaves thick, is what I’m saying)

It’s best to have a hard shape to bend it over, so if you’re making chest armor, have a dress form, make a form, or use your own body, but be careful to cover all exposed skin. this stuff is really warm. For a guantlet, say, use your arm covered in a long sleeve, as in the video, or if you have small wrists, use a glass the right width, or even a jar.

I work with it wearing a pair of dollar store yard gloves, which worked fabulously. Now you only have about 30 seconds of work time, so be sure to mark points on the form and on the pattern piece that will line up, so that when you take the Sintra piece out of the oven, you can flop it over the form, line up the marks, and then smooth it out. I found, in making my chest armor, that it would have been nice to have more hands. I ended up straddling the dress form so that the sides curved inward properly, then pressing with both hands on the chest and stomach area, to make the proper shape.  I looked like I was trying to slay my dress dummy.  It was hilarious when my husband found me that way.

If you have a delicate bend or slight change to make, take out your oven racks, put the Sintra over the coils, until the Sintra goes soft, then you can tweek. If you have a long edge to turn under slightly (because you wont get much more than that) you’ll want to heat a little at a time, so as not to make the whole piece floppy again. Anything you press into it will leave a mark, so be careful to only have smooth surfaces and soft things.

To finish:

If you’re painting, sand the sheen off that son’bitch and prime, then paint.

If you’re building onto it, san and then build and then paint. “Building,” you say, “What’s that?” By building, i mean adding details (for me it was scales which I made with scuply and glued on with some serious cement glue) All these things can be painted and will look seamless when finished.

For added strength, you can coat the whole thing in Resin as I did, and gain a solid non-warping shape. the Resin can be bought at any crafting or hobby storre and used like a varnish. It will fill holes, smooth out surfaces, and basically turn anything you coat it with into a plastic lump. it is a bit heavy, so if you’re concerned about weight, keep the coats thin.

You can drill holes in it, you can stack pieces and glue them together to make layers effects (as you can see in mine) and you can even stick fabric to it.

Hope that helps. If you need anymore info, let me know!

First Pic: Chest plate with several techniques, Sculpey scales, foam inset, and a separate layered piece of sintra over breast area

Second pic: same thing, close up

Third Pic: a gauntlet make of Sintra, built up with more sculpey scales, before painting




6 comments on “Working With Sintra To Make Armor

  1. This is really interesting, You are a very
    skilled blogger. I have joined your feed and look forward to seeking more of your great post.
    Also, I’ve shared your site in my social networks!

  2. What kind of paint did you use for the sintra and sculpey?

    • I used acrylic paint in the squeeze tube. No other paint will stick. You can try spray paint, but be sure to do a light sanding on the Sintra first

  3. Nice armor :D, btw most of people talk about razor blade or box cutters,, what if you used a hot knife (not a normal knife heated, something like this http://www.cabletiesandmore.com/images/thermocutter-Hot-Knives.png), do you think it would still shatter? im trying to migrate from EVA user to Sintra user, so im still shopping materials.

    • I think a hot knife might be able to score the outer “skin” on the Sintra but I’m not sure it’d cut all the way through. It’s a thick, brittle material, that becomes more plastic when fully heated. Like a noodle almost. If you cut a noodle with a hot knife, it might just scorch it. Not sure. Try it on a tiny cast off piece and let me know. I do have some left over, but am not sure where in my garage it has gone.

      Interesting question.

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