Here’s what you’re going to need:
There are a plethora of different types of foam you can choose from. Your choice will all depend on what type of armor you’re making, and what look you’re going for. For most bulky armor (think Mass Effect armor), EVA foam is the way to go. You can buy EVA foam from cosplay shops that specialize in making foam for the very purpose of creating cosplay armor, or you could go the slightly cheaper route and buy foam mats (often used to line the floors of gyms) from a local store (Wally-world, for example). EVA foam is also super easy to shape; just heat it up and bend it. You can also glue a few layers of it together and then carve props from it.
Craft foam, the material you probably used for arts and crafts projects when you were in Kindergarten, is another good option. I use it for thinner armor, such as bracers, and putting detail on to EVA foam armor. However, craft foam doesn’t keep it’s shape as easily as EVA foam.
Sentra is a foam board that is often used to make signs. It is also very easy to shape and retains its shape very well. It’s hardier than the other two foams listed above in that it resists tearing and being punctured. It’s long lasting but it’s also much more expensive. This is what I used when I made my Mandalorian armor.
Something that isn’t foam but pretty nifty is Worbla. It’s a thermoplastic that is easy to heat up and mold but is rather thin and breakable. Because of this, you usually need to create a foam base and then layer the Worbla on top. The Worbla makes the foam more durable and resistant to being punctured. It’s also very useful when it comes to fine details. This option is the most expensive though and one I wouldn’t recommend to beginners.
Now that you’ve bought your foam, you need to cut it with something. A utility knife is your best friend. A pair of scissors will do when it comes to cutting craft foam, but you’ll be hard pressed when you move on to EVA foam. You can buy any utility knife you want, it really depends on your preference. However, I would also advise buying a sharpener. You could buy a utility knife with replacement blades, but, in order to make a clean cut, you would be forced to use a new blade every few cuts. A sharpener saves you time and money and keeps your blade sharp. A sharp blade makes your cuts smooth so that when you glue pieces together later on, your seams look amazing. Oh, and a cutting board is really useful. Don’t ruin your dining room table.
No, you can’t use a blow dryer. It just doesn’t heat up to a high enough temperature to be effective. I bought my heat gun at Walmart for 10 bucks. They’re cheap and are absolutely needed when shaping your foam. Just be careful because these things get really hot. Don’t burn yourself or singe your carpet (I say this from experience).
Now that you’ve got your foam cut, you need to be able to glue pieces to each other. My number one preference when it comes to glue is using Barge Cement. It creates a tight bond that is also flexible which is perfect for foam seams. Another good option is to use is a handy dandy hot glue gun. A high temperature one is preferable. The only downside is that, when using craft foam, the heat of the glue can warp the foam. In reality, any glue will get the job done but you want a glue that will be durable and last.
So you’ve got your armor looking like you want it. Great! Now you’ve got to seal it. This allows for a better, smoother finish after you paint it. Spray paint will also react with the foam over time, if not sealed, and damage it. There are quite a few options available. I personally use Plasti Dip. It’s an automotive product that gives the foam a thin layer of rubber. This makes the foam a little more durable and it also helps cover any seams you haven’t buffed out completely. The only pitfall is that it can be expensive. The other alternative is to use glue as a sealant. I’ve used wood glue and Modge Podge in the past. They work just fine if you only need to seal your foam. Another option is to take Elmer’s glue and mix it with water. Kind of like you’re doing paper mache. I haven’t used this method but I know many who have.
You can really use anything; what you use will depend on the look you’re going for. I have only ever used acrylic paint and spray paint. Normally, I use spray paint for covering large swaths of foam. The acrylic paint is then used for fine details or areas it may be hard to spray paint. Pay attention to the finish of the paint though. A glossy or matte finish is an important distinction for both spray paint and acrylic paint. I’ve known people who have used oil paint before, but I’ve never touched the stuff. Don’t forget to seal your paint if you want it to last a long time!
Well, there you have it. These are just the basics. There’s plenty of other tools that you can use, such as a rotary tool, but they’re not necessarily essential. It takes a great deal of practice to make foam armor so don’t be crest fallen when it doesn’t turn out how you pictured it. Just be patient and try again. Good luck!