I don't recall what chemical we used, but in high school, some friends and I used a base of some sort mixed with tin foil to create a chemical reaction. The byproduct of this reaction was straight hydrogen. We set off quite a few hydrogen balloons. A lot if this was actually done on school property with our chem teacher's approval. Wish I could recall what we used.
Fill 2 liter bottle with acetylen(sp), add a quick shot of oxygen. Screw the lid on.
Fill gas can about 1/4 full, seal top. Let sit in hot sun all day till it puffs up good.
Tape bottle to gas can.
tape tannernite to front side of bottle.
Shoot with tracer round.
post video
Can't say what to expect, but it aughta be good.
3 gal of gas!? Dang... lol
When it comes to gas, less is usually more. Try a 1/2 gal in the same size container next time.