The following is a set of instructions on how to safely and efficiently clean a trumpet. The methods described are those I have found to yield the best results.
Step 1: Before You Begin
Before you begin cleaning your trumpet you will need to gather and take stock of your supplies. You will need a "wire-snake" brush, a mouthpiece brush, petroleum jelly, valve oil, a lacquer polishing cloth or a silver polishing cloth (depending on your trumpet's finish), several towels, and non-bleach dish soap (Bleach can be corrosive to the instrument's finish.). These supplies are displayed and tagged above. You will also need to decide on a wash basin, such as a bath-tub (recommended) or large sink. The wash basin must have running, heated water and room for maneuvering the trumpet safely. Be prepared to apply only lukewarm water, however, and not water that is too hot. Very hot water could cause the trumpet's finish to flake. You will be reminded of this every step. Finally, acquaint yourself with the following terms if they're unfamiliar:
Bore - the interior chambers of the instrument that define air flow path
Lead pipe - the pipe connecting the mouthpiece and tuning slide; part of the horn
Bell - the final, conical section of the trumpet; part of the horn
Valve casings - the chambers that contain the valve pistons; part of the horn
Other important trumpet parts are depicted in the next step.
Step 2: Disassembling the Trumpet
Disassemble your trumpet and place the parts on a towel. The towel will prevent the parts from getting scratched and provide a clean surface. Make sure to locate the towel in a safe place where the trumpet won't get stepped on or otherwise damaged. The disassembled parts, tagged above, are the mouthpiece, the 1st valve piston, the 2nd valve piston, the 3rd valve piston, the 1st valve slide, the 2nd valve slide, the 3rd valve slide, the tuning slide, three valve caps, and the horn. The trumpet may have several screws that hold the 3rd valve slide in place and a "grime gutter." If so, set these aside in a safe place.
Step 3: Cleaning the Tuning Slide
Select the tuning slide and run lukewarm water through it. Apply several drops of soap down the bore of the slide. Take the wire-snake brush and scrub the bore, working up a lather. Do not attempt to thrust the wire-snake all the way through the slide, as this could wedge the brush in the slide's curvature. Rather, scrub the bore from both sides of the slide, working the brush in until it will not freely go further. Now scrub any exterior sliding surfaces (visible as the brass surfaces of the depicted trumpet) removing all residue possible. The trumpet depicted is a "reverse lead" trumpet, meaning that the tuning slide slides over the lead pipe. Thus, there is only one exterior sliding surface on its tuning slide. You may lightly scrub the exterior finished parts of the slide, although any residue on these parts will likely be minimal and can be easily dealt with using the polishing cloth. Finish by rinsing the tuning slide, being sure to eliminate all soap residue. Dump the slide of water. You can dry the slide manually or let it air dry. Select an unused towel and place the cleaned slide on it.
Step 4: Cleaning the 1st Valve Slide
Select the 1st valve slide and run lukewarm water through it. Apply several drops of soap down the bore of the slide. Scrub the bore with the wire-snake, working up a lather. Again, do not attempt to thrust the brush all the way through the slide. Scrub the bore from both sides of the slide, working the wire-snake in until it will not freely go further. Scrub all exterior sliding surfaces (again, these are the brass surfaces of the depicted trumpet), removing all residue possible. You may lightly scrub any exterior finished surfaces you desire. Finish by thoroughly rinsing the slide and dumping it of water. Place it on the towel with the cleaned tuning slide.
Step 5: Cleaning the 2nd Valve Slide
Clean the 2nd valve slide in a similar fashion as the tuning slide and the 1st valve slide: Run lukewarm water through the slide, and apply several drops of soap down the slide's bore. Scrub the bore from both sides of the slide with the wire-snake, working the brush in until it will not freely go further. Scrub the exterior sliding surfaces with the wire snake, removing all residue possible. Lightly scrub the finished exterior surfaces if you desire. Finish by rinsing the slide thoroughly and dumping it of water. Place it with the other cleaned slides.
Step 6: Cleaning the 3rd Valve Slide
Clean the 3rd valve slide in a similar fashion as the other slides: Run lukewarm water through the slide and apply several drops of soap down the slide's bore. Scrub the bore from both sides of the slide with the wire-snake, working the brush in until it will not freely go further. Scrub the exterior sliding surfaces with the wire snake, removing all residue possible. Lightly scrub the finished exterior surfaces if you desire. Finish by rinsing the slide thoroughly and dumping it of water. Place it with the other cleaned slides.
Step 7: Cleaning the Valve Caps
Select one of the valve caps. Run water through it and apply one drop of soap to the inner rim as shown. Scrub inside and out with the wire-snake brush, but with emphasis on removing the oil residue in the inner rim. Although it may seem convenient, do not use the mouthpiece brush for this task, since the mouthpiece brush could transfer oil residue to the mouthpiece, which in turn could transfer oil residue to your mouth. When the oil residue has been removed, rinse the cap and place it on the towel with the other cleaned parts. Repeat this step with the other two valve caps.
Step 8: Cleaning the Horn
Select the horn and run lukewarm water through all pipes and valve casings. Pour a good amount of soap down the horn's bell. Scrub the bore of the bell with the wire-snake, working the wire-snake in until it will not freely go further. Now apply several drops of soap down the bore of the lead pipe. Scrub the lead pipe, working up a lather, and, if the trumpet is a "reverse lead," scrub the exterior sliding surface of the lead pipe. All remaining pipes lead directly to a valve casing. One pipe at a time, apply several drops of soap down the bore and scrub the pipe with the wire-snake, but do not allow the wire-snake to penetrate the valve casing. The wire-snake could scratch the valve casing, causing the valve piston to stick when in use. Scrub all remaining exterior sliding surfaces of the horn. Now apply several drops of soap down each valve casing but do not attempt to scrub the casings with the wire-snake. Instead, attempt to rub out any residue in the interior valve casings with your index finger (Valve casing brushes do exist, however this instructor does not recommend their use.). You may finish cleaning the horn, if you desire, by applying soap to and scrubbing lightly any exterior finished parts with the wire-snake brush or your hands. Rinse all bores, valve casings, and exterior surfaces with lukewarm water. Dump the horn of water and set the horn with the other cleaned parts.
Step 9: Cleaning the Mouthpiece
Select the mouthpiece and run lukewarm water through it. Apply several drops of soap down the bore of the mouthpiece. Select the mouthpiece brush and scrub the bore from both sides. Do not attempt to thrust the mouthpiece brush all the way through the mouthpiece's bore, as the mouthpiece brush could get wedged. Instead, work the brush in until it will not freely go further. Scrub all remaining surfaces of the mouthpiece. Rinse the mouthpiece and place it with the other cleaned parts.
Step 10: Replacing the Slides
Apply petroleum jelly to all exterior sliding surfaces, both on the horn and on the slides (Petroleum jelly is an ideal lubricant for slides because it doesn't leave residue, protects metal, and has a consistency that doesn't allow slides to slip, however if you desire minimal friction on trigger slides, use valve oil instead.). Replace the slides in the horn and wipe away any excess lubricant. Don't forget to replace the 3rd valve slide screws. Take this time to replace the valve caps as well.
Step 11: Cleaning and Replacing the Valves (Save This for Last!)
Select one of the valve pistons and run lukewarm water over and through it. Apply several drops of soap to the piston. Rub the soap around the exterior of the piston with your finger, attempting to work off any residue. Do not attempt to scrub the piston with a brush. A brush could scratch the piston and this could cause the piston to stick when in use. Now, using your index finger, attempt to rub out any residue in the air channels of the piston. Rinse the piston. Quickly, before the piston has a chance to dry, apply a good amount of valve oil and replace the piston in the correct valve casing. (The resistance between the water droplets from the rinse and the oil make the water-oil combination a super-slick lubricator, and this is why we cleaned the pistons last, so they could be quickly replaced in the valve casings without losing any of this water-oil combination). Repeat this step with the remaining two valve pistons.
Step 12: Polishing the Trumpet
The trumpet should now be in ideal playing condition, but won't be much improved aesthetically until polish is applied. However polish doesn't just create the all-important shine, it also protects the instrument from tarnish. For best polishing results you may wish to obtain silver or lacquer polish (apply as directed). However, far more popular among today's brass instrumentalists are the easy to use, satisficing polishing cloths. Select the polishing cloth (either a lacquer polishing cloth or silver polishing cloth depending on your trumpet's finish) and rub all finished surfaces until you are satisfied with the instrument's luster. If you polish the mouthpiece, be sure to re-wash the mouthpiece thoroughly: polish is poison.
Step 13: The Finished Product
Finish by replacing the grime gutter and tuning the instrument if necessary. Your trumpet should now be good to go!