well this trick has been around for years as you say. It's a little tricky getting the soot where you want it,and it's messy. You'll have little bits of burn't acetlyene floating around all over the shop. What works just as well is the plastic sprue that plastic parts in a model kit are attacted to. Either way the effect is cool. Just make sure you do it outside.and don't touch it until you get clear on it.