Cleaning the Cork Barrel
Dirt accumulates inside the cork barrel. Clean out this dirt with a small brush, feather, or pipe cleaner. Use some trombone oil to loosen. If you don’t keep this dirt out of the cork barrel, the outside slide will gradually draw it out and it will foul the action. Often this is the cause
of a certain mysterious slide trouble. After the trombone is thoroughly cleaned and oiled, the slide action is fine for awhile. Then it begins to drag and bind. The reason is this: the dirt is being loosened and dragged out of the cork barrel. If your trombone has a spring stop instead of the cork stop, the same precautions apply.