... and 100 small boxes in a big carton containing 20 kg, or by users opinion. (3)Burning timeThe hexamine ... with 20 gram can burn with 15-20 minutes, with strong flame, and the flame temperature ... , odorless, non-toxic, no residue after burning, and it takes about 15minutes to cook 250 gram rice or ... it on the slate, surface, sand beach, and then ignite it. hexamine fuel