Proper instrument maintenance is an important part of any musician's responsibilities. Brass instruments must be cleaned frequently in order to counteract the effects of gunk buildup from oil, grease and contact with warm moisture and mouth germs. With a baritone horn (euphonium), a thorough cleaning process involves a full water submersion bath as well as disassembling the horn to scrub its component parts. Cleaning your baritone horn on a regular basis will not only improve its performance, it will leave your horn looking and smelling its best.
Fill the bathtub about half full with warm water, then add about a half gallon of white vinegar. This will help remove gunk from the inner workings of the instrument.
Take apart the horn and soak the pieces in the tub. Remove all the tuning slides and place them in the tub, taking care to set them down gently to prevent denting them. Take the valves apart partially; unscrew and remove the pistons, unscrew the key caps from the pistons and remove the felts (set these aside so they don't get wet) and place all parts, along with the larger pieces of the horn, in the tub. Let these parts soak for a half an hour.
Clean the horn with your wire snake. Thread the snake through each tuning slide and through the hollow portions of the valves several times. Rinse the brushes of the snake after each swipe in order to remove any gunk you've collected. Repeat brushing with each section until the snake brushes come out clean. If necessary, remove some of the buildup by running valve sections under the faucet.
Use a rag to remove old, dirty tuning slide grease from the outside of the tuning slides. If the slides are particularly dirty, use a small amount of dish soap on the rag to break up the grease and remove it.
Wash the horn with a washcloth. Give the horn a swipe with a wet washcloth to remove any dust and water spots that have accumulated. Do this right before toweling the horn if you want it to shine and look its best when you're done.
Remove the horn from the bath and dry it. Use a large towel or two towels so that you can not only absorb the moisture, but dry buff the components without the towel sticking to the brass from moisture.
Reassemble the horn while greasing and oiling it. Place oil on the inner parts of the piston valves before putting them back together. Apply a small amount of grease to the inner parts of the tuning slides as well.