Steel pipes are one of many kinds of pipes designed to smoke tobacco in. All tobaccos have different aromas and all different kinds of resins. Resin is the gooey tar-like substance left in the pipe after smoking a bowl of tobacco. It can vary in color from black to brown, and when it hardens on the surface, it can be difficult to remove. You'll need some basic household ingredients to clean the resin out of your steel pipe, and you may need to purchase some things, but all in all, it is not very expensive to clean your steel pipe.