Everyone loves some good armor. It's also nice when it's not terribly expensive, and it's lightweight and easy to wear.

For this project, I will be using foam. There are lots of tutorials on working with foam, so I will not focus on that, just what I did to make the armor. For resources on working with foam, I'm a big fan of:

Bill Doran's tutorials and books on punishedprops.com
The youtube channel for Evil Ted Smith: https://www.youtube.com/user/evilted40

Be sure to do your research before starting a project like this. It makes things go a lot faster and easier.

Step 1: Materials

For working with foam and making the breastplate, you'll want:

An good knife and some blades
A heat gun
Contact cement glue
Markers
Hot glue gun with lots of glue (you'd be surprised how much you go through)
Cutting Mat
Cardboard (for templates)
Foam gym mats
Some thinner craft foam for the details (I tend to like 3mm, but it's always nice to have different thicknesses lying around)
Plastidip (mod-podge is also often recommended)
Spray paint
Acryllic paints

Step 2: Sketch Your Idea

Everything starts with an idea. This breastplate I designed for a King Triton costume. So I wanted it to have a mermaid flair to it. It was also designed to be shorter and just go down to the natural waist line. Take these considerations into account as you design. Look up lots of references beforehand. It really helps to get a more genuine look.

Step 3: Get Measurements

Next, you need to take measurements. This might require help from a friend. DO NOT try to measure yourself. Especially when it come to the torso. It too often leads to inaccurate measurements as you bend around. For the front of the breast plate, I measured:

from the neck to the natural waist line
from side-to-side across the chest
from side to side across the natural waist
around the neck.

Make the same measurements as well for the back. Be sure to add and an inch or two of "ease" for the side to side measurements to give yourself breathing and wiggle room.

As you can see, I also took a few other measurement just to help out a little more on the shape of things. Measurements required also depend on the design of your breastplate.

Step 4: Make a Cardboard Template

The next step is to now make a cardboard template of your design. This will help with transferring your design to foam. It is also a good way to test that your measurements were correct. It would be a shame to cut it out of foam and realize that is doesn't fit.

Once you know the main piece fits, draw on some of the details and cut those out of your main template. Just do one side to help ensure symmetry. I cut out the pectoral and the shoulder blade. I also eventually cut out a few other details, such as the abs.

Step 5: Start Cutting Foam

Using your templates, transfer the designs to foam. Be sure to flip your patterns over to make a mirror image of the pieces so you don't end up with two right pecs. For my design I purposely cut the pectorals and the shoulder blades separate from the main part to add more depth and detail. Add an inch or so to the main body to glue the pieces to (seen above).

Once cut out, I used a heat gun to heat up the pecs and the shoulders, and gave them a more rounded form. Once they were the desired shape, I used a rotary to to grind down and smooth the edges. I also cut out the abs from other foam that I had and shaped and smoothed those.

Step 6: Start Basic Structure

Once the parts are cut, shaped and smooth, layout the patterns and mark their spots with a marker. Then glue everything down. I like using a good contact cement glue. Test the fit (maybe by using some tape if you haven't done any strapping yet).

Step 7: Add Details

Once you are satisfied with the basic shape, you can start adding details. I put cheap pieces of paper over the form and drew out designs for the detailed bits. I then transferred them to foam. Have fun with this stage. Realize the it is often the layers and details that make the coolest looking costumes. Use your sketch as a guide (because paper is cheap).

Step 8: Paint and Add Strapping

Once you are satisfied with the details, you are ready to seal the foam and paint. I first go over with a heat gun to seal the foam. Then I give it a few coats of Plastidip. I realize that there are many other methods, that's just one that I like.

Once the foam is sealed give it some primer, then hit it up with a nice coat of metallic spray paint. I went with a gold color on top of black. I really liked the look of that.

Once I had given it a few layers of gold, I weathered it with a little bit of watered-down acrylic paint. I mixed some browns and blacks to help pull out the details. Some people may also want to add some grease and rust as well. Have fun with this stage. Look up some videos of how other people do weathering and what colors they use. There is some cool stuff out there on the interwebs.

I then proceeded to add some velcro strapping to hold the front and the back together. Some people prefer buckles. Velcro is cheap, and I had it ready-to-use. Just be sure when you use velcro that you use enough of it on the armor to ensure that things hold in place, and that you face the hook side away from your person. It makes things a lot more comfortable.

Step 9: Enjoy!

Now go out and enjoy your armor. I eventually added some pauldrons and vambraces as well (maybe I'll cover those in another tutorial). Like I said before, it's the details that makes this awesome. Enjoy and comment below with pictures of what you created.