Brass instruments have traditionally been cleaned with a combination of soaps and chemical baths, accompanied by a good deal of hand scrubbing. In recent years ultrasonic cleaners have come into the picture, offering a different cleaning method. Which method gets your horn cleaner, which is safer for the horn (and you)? How do you choose?
As a brass instrument is played, deposits build up on the inner surfaces. These include old grease and oil, food particles, dental plaque and bacteria, calcium, and copper carbonate, the material formed by the reaction of the acids in your breath and the copper in the alloy. Copper carbonate builds up green, rock-hard deposits. It’s the primary cause of sticking and other action problems in rotary valve instruments. If the mouthpipe is brushed out once a week or so and the instrument is oiled frequently enough, a brass instrument can go for years between Chem/Ultrasonic cleanings. In actual practice, however, this rarely happens and a cleaning is needed every year or so.
A Chem Clean starts with a scrub with brushes and detergents to remove old oil and grease. The instrument is immersed in a mildly acidic solution which dissolves the calcium and copper carbonate. Areas of heavy buildup can be addressed with acids on a
q-tip. Then the instrument is scrubbed again with detergent to remove any residue and is re-assembled.
Ultrasonic cleaning replaces the hand scrubbing with sound waves. The disassembled instrument is put into a tank of cleaning solution and bombarded with sound waves. The sound waves cause microscopic bubbles to form in the fluid. These bubbles immediately collapse, converting the sound waves into kinetic energy. This process, called “cavitation”, creates the scrubbing action that cleans the horn. One of the big advantages of ultrasonics is that that scrubbing action reaches all through the inside of the horn, even into areas unreachable by brushes.
When using ultrasonic cleaners it’s important to be aware of their power and potential for damage. The microscopic bubbles are very good at finding their way into the pinholes left by dezincification and opening them up. So, older instruments and instruments that show any signs of dezincification (red rot) should not be ultrasonically cleaned. Ultrasonic cleaning can also remove some lacquers. So, it’s important to use the least power and the shortest time that will do the job.
Some people have the misconception that ultrasonics replace acids in the cleaning process. This is not the case. The acids are needed to dissolve the calcium and copper carbonate deposits. The cleaning solutions we use are mild enough to be handled without gloves. We have tested samples for up to four hours of immersion with no measurable loss of metal. (Repair shops and manufacturers used to use Chromic acid to produce a bright brass surface. This material did remove metal and is also a carcinogen. It has been banned by the EPA although, amazingly, you can sometimes still find people using it.)
In our shop, a typical cleaning may involve both ultrasonics and traditional techniques. We choose the combination that’s safest and most effective for the instrument.