This Mark 3 Iron Man costume is very accurate to the movie's. I spent lots of time trying to get all the details in. It is mainly made of Poster Board, Foamies (arts & crafts thin foam sheets), a ton of Hot Glue(I think I used 140 sticks or so including the helmet and arc reactor), Mod Podge, and newspaper to thicken and seal the posterboard with Mod Podge. Mod Podge was also used to seal the foam to make painting easier. The entire construction of the costume took about 1 month on and off or 100 hours of labor. Most of the time was spent test fitting and cutting templates that fit me correctly.
The Arc Reactor was made by following the instructables Arc Reactor DIY using surface mount LED's and molding plastic.
The Helmet took about 40 hours of work (including drying,sanding,bondo, and painting). It was made by first creating a mold of my head as the base using Plaster Bandages you can get from arts and crafts store (Plast'r Craft is the brand). Once this dried I built up the Iron Man Mark 3 shape by using a very thin aluminum mesh(held down by hot glue) you can get from arts and crafts stores as well near the clays. Once you think you have the shape down, lay down more plaster bandages. If it doesnt look right like my first attempt(no chin) then repeat process with more mesh and bandages. Then, cover the outside of the helmet with bondo in small increments, sanding in between each application to a smooth finish. After that is just painting.
Painting was done using a Gloss Colonial Red and a RustProof Metallic Gold. I used lots of taping to make sure the colors didnt mix at all. Good luck its a lot of work but will be the talk of all the parties.