Intro: Introduction to EVA Foam
EVA Foam is a great material for constructing costumes and props of all different kinds, from period armor and swords to slick futuristic robots. It is especially beloved by cosplayers and prop makes because it is lightweight, cheap, and can easily be cut, carved, and even heat shaped to create interesting forms. With enough skill and the right tools and patience, it can be finished to look like almost any material.
The world of EVA foam costuming is a rabbit hole, and many foam armor projects are ridiculously complex and take hundreds of hours and a lot of patience to build, but this is an beginner lesson designed to introduce you to some of the basic techniques through the creation of a relatively simple shoulder piece for a superhero costume. If you are intrigued after this instructable and want to dive deeper, check out this collection of superhero related projects where you'll find a lot of other great EVA foam tutorials.
This instructable is also part of my How to Become a Superhero collection which is a series of tutorials that walk you through designing and constructing your own superhero costume. Check out the rest of this collection for instructions on how to create more pieces of the costume.
Introduction to EVA Foam (*you are here)
Step 1: Tools and Materials
Step 2: Types of EVA Foam
Because EVA Foam is used for so many purposes besides costumes, it can be sourced from a lot of convenient places in slightly different forms. Some kinds will be denser or softer than others, some will have a texture on one or both sides, and you will find it in a wide variety of thicknesses.
In order to get EVA foam, you used to have to buy products intended for other uses like thick tiles used for floor covering, softer floor mats that come in rolls, and smaller sheets or rolls of thin craft foam. The first two can often be found at hardware stores and will usually have a texture, which can be nice if you are creating certain kinds of armor, but if you want a blank slate to work on it can be annoying. Craft foam sheets and rolls, which are thinner and smooth on both sides, are sold at places like Michaels.
EVA foam has now become such a popular material that now there are some dedicated sites selling foam specifically for costumes. My go-to site is TNT Cosplay Supply - they sell large sheets of smooth, dense high quality foam in both black and white and a variety of thicknesses.
To create costume pieces with both structure and details you'll need to have a few thicknesses on hand. For my shoulder piece I used 8mm and 4mm foam, and for the core of my Worbla headpiece (which we'll talk about in the next lesson) I used 2mm.
Step 3: Patterning Foam Accessories
There are many ways to create patterns for EVA foam accessories, and the best methods for patternmaking will vary depending on what kind of accessory you're creating. My go-to patternmaking method for most accessories is to make a mock-up in paper and oak tag (thin cardboard used for pattern drafting) using a dress form and my own body. If you don't have a dress form you can just use yourself, or get a friend to act as your mannequin while you get some basic shapes and proportions.
This method is good for pieces like this shoulder armor that don't have to fit as precisely against the body. If you are making something more fitted, like a breastplate, you can use the tape and saran wrap method, like ErikaT5 uses in this great Leather Corset Instructable. This is saran wrap trick a very popular and effective method for creating patterns for both foam and Worbla accessories, and I'll show you a version of it in our lesson on Worbla.
To pattern my shoulder piece I started by pinning a piece of pattern paper to my form and drawing the basic shape of my piece while referring to my sketch, I also marked important points like the shoulder seam.
Then I took the paper off, edited my lines a little and traced the shape onto a piece of oak tag with my spiky tracing wheel. I cut out two copies of the shape to see what the outline of the whole thing looked like on the form, and then refined it to get a shape I really liked. I also tried it on my own body to make sure the shapes and proportions were working on an actual human.
Since my design was going to consist of several topographic layers of foam I just drew the outlines of the layers onto the base piece and fiddled around until I had something I liked.
I decided wanted to cut-out the foam over the shoulder where the circular shoulder detail was going to sit. To create the pattern for the shoulder detail, I cut a flat 'O' a little bigger than the one I wanted to create and then sliced it on two sides and taped it back together in a cone. Once I had something the right size, I cut it open again to create a flat pattern.
EVA foam can be formed through heat shaping, so to account for the areas that I knew I was going to heat shape later (such as around the neck) I slashed into the paper to give it something close to the proper shape. This is a technique that is used sometimes in draping to get fabric to fit around a form, but it works a little differently here because the slashes actually allow the stiff oak tag to mimic the more flexible qualities if the foam.
To create actual pattern pieces for each layer I traced the outlines I had drawn onto separate pieces of oak tag and cut out a separate piece for each, adding some extra on the edges of the two lower pieces so they could be glued to each other where they overlap.
Now you're almost ready to start cutting out your foam pieces, however there is one complication. The tricky thing about creating paper patterns for foam is that unlike the paper, the foam has a thickness, so on a curved surface, a flat paper pattern can't be a fully accurate guide for cutting out your foam pieces after the first layer.
One way to get around this, is to not pre-make your whole pattern like I did, but instead create your pattern as you build. With this technique, you would cut your base piece out of foam, then, with that piece on the form cover it with paper or masking tape and draw the pattern for your next layer right on the tape. I do something similar to this, but I like having my pieces already patterned because they give me a guide to work with, even if they are only an approximation. I will show you how I do this as I cut out my pattern.
Step 4: Cutting
Once you have a pattern for the base shape, you can start cutting out the foam. We are going to build this armor from the base layer up, creating the exact shape of each layer as we go.
Trace the base pattern onto your foam with either a marker or a sharp object, like an awl or a seam ripper that makes a small groove in the foam.
Over a semi-soft cutting surface like a cutting mat or wood cutting block, use a sharp X-acto for craft knife to carefully follow the lines you've traced. Hold the foam down with your other hand as you cut, but be careful not to put your fingers in the way of the blade. No matter what your superpower is, it's always better to have fingers.
Try to cut with your blade held at a right angle so you don't create a beveled edge on your foam, and do your best to cut all the way through in one smooth motion. If you have to stop and start or go over your cuts again you will end up with jagged edges which are a pain to fix. Trouble cutting through the foam is usually a sign of an unsharp knife.
MAKE SURE YOUR BLADE IS SHARP!!! Seriously, foam doesn't seem like it would dull a blade so much, but I change blades ridiculously often when I'm cutting. As soon as your blade stops sliding through the foam with very little effort, change your blade if you don't want jagged edges.
Once the base pieces were cut out I pinned one of them on the form over my paper pattern to make sure it was positioned right, then I used a few pieces of double sided tape to stick a slightly larger layer of thinner foam over the base layer.
Keeping the two stuck together in the curved position, I took them off the form and traced the outline of the base piece onto the thinner piece from beneath.
You might think this piece could be the exact same size as the one below, but because the bottom piece has thickness and is curving, the top piece actually needs to be slightly larger than the bottom piece.
I cut out the outline of this new layer, and then used my original paper pattern as a guide to draw the inner cut out, moving it a little as I went to cover the whole piece.
Then I taped the two pieces together on the form and used the same method to create the third layer with foam the same thickness as the base. I think varying the thickness of the foam when you're creating details can depth and visual interest to a piece.
Once I had the three layers cut out on one side I used them to trace and cut out mirrored pieces for the second side (and if you think you might make this design again it's a good idea to also trace off these new pieces onto paper to create a pattern you can keep).
Step 5: Heat Shaping
One of the most fun things about working with EVA foam is heat shaping. Adding just a little shape to some otherwise flat pieces gives your design a much more interesting, sculpted look. You can't bend foam, especially the thicker kinds, in super dramatic ways, but you can definitely create some nice bends and curves.
To shape your foam take a heat gun and wave it over the area you want to shape, moving it around and keeping it about 4" away from the foam. You will start to notice that the surface of the foam goes from matte to slightly shiny as it is softened somewhat by the heat. If it starts to bubble or form little droplets you are heating it too much or holding the gun too close.
Flip the foam over and use the gun on both sides of the area you want to shape. When you've heated it for about 30 seconds, turn of your gun and try shaping the foam with your hands. Stretch, pull and form it into the shape you want. If it isn't forming enough heat it more and try again, sometimes it takes a few rounds to get a shape you want. Once you've gotten the right shape, try not to heat that area again so you don't undo your work.
You can also try using other objects to help you create shaping. If you wanted to create sharp angle, you could bend the hot foam over the edge of a table for example.
Depending on your design it may make sense to heat shape some parts before you glue, and heat shape some parts after. On this design I shaped the collar flare before I glued the layers together, but I waited until I had glued the shoulder circles together to add a little shape to them before I glued them to the rest of the piece.
After everything was glued together, I added a little shape to points in the back.
If you have rough edges on your pieces you can also smooth them out a little by sanding them, hitting them with the heat gun, and then smoothing them with your finger while they are still warm. For a really professional finish I've seen people use a blow torch on sanded foam edges which really smooths them out.
Step 6: Gluing
When I was learning to work with EVA foam I had a lot of conversations with people who built foam armor designed to withstand foam weapons combat. They all told me that the absolute best glue to use is DAP Weldwood contact cement, and that it has to be the "Original" kind in the red can, not the water soluble kind in the green can. So that is what I primarily use on my foam projects.
I have also found Barge to be effective, and it has a thinner that you can use in case you make a mistake and need to remove something. And when you are gluing together the edges of foam rather than laminating layers, hot glue works well too.
DAP is rather nasty stuff and it has a fairly long curing time, so it's not the most convenient material, but man does it work! However, you definitely need to use it in a well ventilated area where you will be able to leave you piece to cure for at least 24 hours, and make sure you wear gloves while you're working.
Before you glue your pieces together you should use a marker or sharp object to trace the outlines of each piece onto the corresponding piece from above and below so you know where you'll need to spread your glue.
Lay your pieces out in your ventilated area on top of paper or a drop cloth to protect your work surface. When you're ready, use a disposable brush to spread a layer of glue on both of the surfaces that will be glued together.
Your layer of glue shouldn't be too thin, but not too gloppy either, something like this:
Before you stick the two pieces together you need to wait for the glue to soak in and dry so it no longer has this wet appearance. If you're working with large areas the glue on one side will often be dry enough by the time you've finished the second side. When it's ready it will look like this:
Now very, very carefully stick the two sides together. Once this glue sticks, it doesn't come apart, so make sure you are lining it up right the first time. Start at one end and carefully work your way along a seam. Try not to stretch or crush the foam as you go, but if you do find that your pieces aren't lining up you can sometimes stretch or crunch one to fit the other.
For pieces like the shoulder that are curved, you need to glue the layers together curved, not flattened out, or they won't line up right.
Sometimes you have to go back and forth between gluing, shaping, and marking exactly where pieces should sit on each other. I glued and shaped the circles, then aligned and marked their position on the shoulders before gluing them on.
For smaller details like the slats on my shoulders, it can be easier to just create and glue the foam pieces as you go rather than making patterns for them.
Step 7: What's Next?
So what have you decided to create? Shoulder piece? Breastplate? Bracer? Once you've glued something together with your EVA foam, you'll probably want to finish and paint it too match the style of your costume. In my instructable about Painting and Finishing EVA Foam and Worbla, I'll show you how I finish and paint my foam accessories to make attractive and durable. And, also check out my Introduction to Worbla instructable to learn about another amazing cosplay material that can be used on it's own or even combined with EVA foam, to create some mind blowing costume pieces!