She's a huge fan of spider-man, so I decided to create her a lost foam Casting of a spider man mask.
I won't post any descriptions about how I created my foundry furnace or burner, as there is a plethora of information on the web about the topic. However, I have added a couple of links below that I found useful during the design process.
Burner design -> http://ronreil.abana.org/design1.shtml#Preview
Furnace desgin -> http://www.backyardmetalcasting.com/refractories.html
WARNING!!!: You have a brain... USE IT! Building and working with a foundry furnace is "NOT" child's play. It can be very dangerous and anything that happens is not my responsibility! Please take the time to read and study all the safety procedures that are available on the net, as well as your local library. You are responsible for yourself and your own safety.
Also, burning foam is very nasty stuff and is likely not healthy to breathe. Wear a respirator!!
Step 1: Creating the piece in foam Insulation
Unlike Spike3579, I did not have the advantage of cutting my hearts on a CNC router, so the first portion of this instructable details how I sculpted Spider-Man out of Blue foam insualtion.
I began by printing and cutting out an image of Spider-man's mask, and tracing the outline of the mask and the eyes, then cutting out the overall mask. Ideally I would be able to cut this with a hot foam cutter, but have not created one yet, so I had to do with a very sharp knife.
Bear in mind that EVERY SINGLE DETAIL that you make in your foam piece will show up in your aluminum casting, so be sure you take the proper amount of time to work to get your foam piece just right, because it is much easier to work in foam than metal.
Once the overall shape was cut out I used 220 grit sandpaper to sand a bevel around the whole of the mask to make it look less blocky. I then used a soldering iron on medium heat to Melt out the eyes. There may be a better tool for this, but the low heat from the soldering iron allowed me to create a depression for the eyes without burning through the foam... I think it turned out fairly well.