How cool is a book that gives you detailed instructions on how to make gunpowder? Pretty damned cool. Turns out there is more to making black powder-as author William Gurstelle prefers to call his gun powder-than Captain Kirk made it look when was kicking Gorn ass with a bamboo cannon. For one thing, you need pure ingredients. William advices that you make you own charcoal, since the stuff you use in a barbeque is full of all kinds of impurities. He recommends buying the sulfur and saltpeter. Once you have made the black powder you can go on to make…