List of materials
1. Sulfur- can be powder or pellets or anything that is plain elemental sulfur. You can get this at a farm supply store. I got 50lbs for $30. It can have impurities up to maybe 20%. More impurities equal less strength. If you don't want large quanities, buy some from here>http://doitbest.com/Main.aspx?PageID=64&SKU=722367&utm_source=Froogle&utm_medium=FREECSE&utm_term=722367&utm_content=6790&utm_campaign=DATAFEED
2. Aluminum foil- optional- I got this at Cosco for $15 for two rolls. This comes out to be 5 pounds of aluminum. If you don't want large quanities, get a roll from the 99 cents store. This is used as an aggregate.
Edit: I found Aluminum foil to be a great aggregate, but you can use other things like rocks or sand to make it stronger. Also, try painting the sulfur directly onto some fiberglass and layer it like a surfboard. I find that makes for a very strong sheet of plastic. Just make sure you get the sulfur down into the cracks because it dries quick.
3. LDPE - get this either from recycled plastic, such as milk bottle caps and other flexible lids, or online here>> http://www.birchplastics.com/
or here>> http://www.amazon.com/LDPE-Density-Polyethylene-Length-White/dp/B0013HL0OY/ref=sr_1_7?ie=UTF8&s=industrial&qid=1267304312&sr=1-7
this comes out to about 7 cents per cubic inch, or 2 dollars per pound.
75% LDPE + 25% sulfur- about 1.70 per pound
25% sulfur + 75% aggreagate (sand and rocks)- 0.15 per pound
**all percentages by weight***