Ask Dave: Why Do My Valves Get Stuck?

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I’ve fielded so many questions recently about stuck valves that is occurred to me that most players do not understand why their valves get stuck.

A horn comes from the maker with valves that work. The rotors are designed to float on a thin film of oil in the bearings. There is an engineered gap between the rotor and its casing, and the lubricant fills up that space. The total diameter of this gap is about .0005″ in the bearings and about twice that, or .0010″, in the casing.

Mind the gap

It’s not much space, and unless the oil is continually between the two metal surfaces other “stuff” can get in there. Dirt and grit can get in there from outside the horn, but that is a actually a rare occurrence. More likely to fill the gap are corrosion and built up deposits, both of which are a result of saliva and condensate from the player’s breath.

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The condensate is itself acidic. When the oil evaporates the acidic condensate readily reacts with the metals in the alloy. It will dissolve the zinc in the brass and will dissolve or oxidize the copper.

Introduced water vapor and saliva also contain particles from inside the player’s mouth. These particles go into solution and mix with the other dissolved things, such as metals. When the oil and the water both evaporate, the mixture that’s left often contains a mix of calcium carbonate, copper, and zinc, which forms a hard light green deposit.

Treatment and prevention

Generally, hard deposits and corrosion will not be removed by washing with detergents, which will only remove oil, dirt, and grit. These deposits can only be removed with either acids or ultrasonics.

Minimize introduced particulates by rinsing your mouth or brushing your teeth before playing. Minimize the chance of corrosion and deposits by keeping your horn oiled and empty of water.

University of Horn Matters