The Halo Reach Spartan costume was made from two kinds of foam. The kind that you put under a sleeping bag when camping, and the kind of interlocking foam used to support a treadmill. I measured and made cardboard mock ups then cut the foam out. Had to make a lot of right angle cuts for things to fit correctly. For the parts that were curved I used a heat gun and heated then formed the foam into the shape I wanted.
Finally I used a mix of water and multipurpose glue to seal the foam. Then put a primer coat and a base coat and added weathering and battle damage. The face shield is from party city it is called the no face mast. I just cut it and formed it to fit the opening. I added LED lights to the chest and back plate as well as the helmet. The boots are old motocross boots I got from a yard sale.
I had very little time to work on this so I am pleased with the outcome considering. The best part was when my son saw the finished helmet for the first time….he wanted to wear it to school! LOL