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I'm renting a Yamaha 201 Euphonium. After I practice every day, I empty the condensation using the water key first, then removing the valve slides to empty any residual condensate. I noticed that moisture accumulates on all of the valve slides (outside, not inside. The moisture does not accumulate on the tuning slide and water key. Is it normal for condensation to accumulate on the exterior of the valve slides? Thanks

We have an industrial HVAC expert on this board, a Mr. D.W.

Let's encourage them to speak up, here.

Thanks, @bloke

I can’t envision a circumstance in the normal use case in an unhumidified room where the physical conditions would be right for exterior condensation on an instrument during playing.

I could imagine an improbable set of circumstances where a very cold instrument is brought into a humidified room, and condensation might form briefly before the instrument warms up, but I wouldn’t imagine that that’s the case here.

Condensation forms when a surface is at or below the dew point of the ambient air.

For example, right now the conditions at my house are:

• Outdoor air: 29 deg, 41% RH

• Indoor air: 73 deg 19% RH (because I have steam heat, I have a bit higher indoor RH than I would expect based on the outdoor conditions)

The indoor conditions yield a dew point temperature of 28.78 F.

So if my instrument was sitting outside all day, and I brought it inside, it MIGHT yield a tiny bit of exterior condensation.

On the other hand, if you were to bring an instrument from a 70 deg air conditioned space outside in the high summer and it was 90 F 85% RH, then you would see condensation till the instrument warms up.

I would suggest you look for poorly fitting slides where moisture could be leaking out. Joe, that’s your department.

Don Winston