Building a balloon
These are instructions for building balloons the way DofT does it. For best results, use dark colored HDPE trash bags - The same kind of plastic that plastic grocery bags are made of (if they haven't banned them in your area yet...) except trash bags... and black. The thin crinkley type of bag is what you're after - the smoother less crinkly bags might work, but your best bet is to find the thinnest, lightest (weight-wise), darkest bags you can get your hands on. DofT has used everything from small wastebasket sized bags, standard 13-gallon bags, on up to large industrial bags, but they were all the thin HDPE bags. Even though different sized bags may have slightly different proportions when cut apart, the basic design and process should be essentially unchanged.