Flute Shrinkage in Dry Weather

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tstermitz
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Flute Shrinkage in Dry Weather

Post by tstermitz »

I live in Colorado, USA which has a relatively dry climate. Despite that, the humidity in my house is reasonable much of the year except now that the heat is frequently on. Daily playing is insufficient to keep the flute properly humidified, and save my flute in a plastic box with guitar humidifier method, which is easy to keep at 40-50% humidity.

I notice that the rings on my flute become loose when the humidity drops too low, meaning that the flute has shrunk.

I have one question, though:

If a flute shrinks, do the joints typically become tighter or looser?
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Re: Flute Shrinkage in Dry Weather

Post by fatmac »

I think they will loosen, if the wood shrinks.
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Terry McGee
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Re: Flute Shrinkage in Dry Weather

Post by Terry McGee »

tstermitz wrote:If a flute shrinks, do the joints typically become tighter or looser?
I think it's not capable of an easy answer. Let's imagine that the flute has no ring, and has cork for the lapping. As the weather dries, both tenon and socket will shrink. The gap between them will also shrink at the same rate, putting a little extra pressure on the cork, slightly tightening the joint. If wetter weather comes along, they will all expand, slightly loosening the fit. Note that it would be only a very slight effect, and probably well within the capacity of the cork to absorb.

But now pop a metal ring on the outside of the socket, and it will constrain the socket from expanding. So in wetter weather, the expanding tenon will be met with the resistance of a constrained socket. It's even possible that the wood of the socket will expand inwards, as it can't expand outwards. I'd expect that the fit would tighten, whereas without the ring, it would have loosened. But if the weather dries, at some point the socket will shrink away from the ring. We are in non-linear territory.

Now replace the cork lapping with thread wrapping. Now both tenon and socket are constrained from expanding, but not constrained from shrinking. Damp weather probably won't change things much, as both remain constrained. Although the joint might tighten if the socket wood expands inwards. But dry weather will have the tenon shrinking away from the thread wrap, loosening it, and so loosening the joint. Until perhaps the socket wood shrinks away from the ring, and again we are in non-linear territory.

At this point with the thread packed joint loosening, you might be tempted to add some more thread, which is how serial strangulation can start, particularly in softer woods (like boxwood) and if the tenons are thin as they were with later 19th century flutes.

Complex, eh?
Gromit
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Re: Flute Shrinkage in Dry Weather

Post by Gromit »

I think it's not capable of an easy answer.......
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Casey Burns
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Re: Flute Shrinkage in Dry Weather

Post by Casey Burns »

Years of observations indicate that both the joints loosen regardless of thread wrappings or cork, and that rings loosen as well, when the flute is subjected to low humidities. The rings often give an early warning that shrinkage is occurring. In Colorado its not uncommon to see humidities in the single digits in wintertime stretched over months. Its also easy to overestimate how well the flute is being humidified. A digital humidity gauge is a good tool to monitor the flute with.

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Re: Flute Shrinkage in Dry Weather

Post by Conical bore »

I agree with Casey: the first step is knowing what your room humidity level is throughout the year. Don't trust the cheap analog dial gauges that come in something like a guitar case. A sling psychrometer is the tried-and-true (and cheap!) method, but even inexpensive digital hygrometers are reasonably trustworthy now. Just don't buy the least-expensive ones you find.

I've always been a believer in humidifying the room you keep your musical instruments in, rather than trying to humidify a storage box or instrument case. Humidify the whole house if you can afford it, especially in a place like Colorado where heating drives down the humidity in Winter. But fan-blown cool air room humidifiers aren't that expensive for a music room, and it just takes some effort to refill the reservoirs when needed.
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Re: Flute Shrinkage in Dry Weather

Post by tstermitz »

I do have one of those digital humidity monitors. In the plastic box with guitar humidifier it runs 45-60%

Colorado plains climate is dry but the humidity inside the house is in the 35-45% range for much of the year, approximately the months from March to October. In the months when the heat is frequently running the humidity in the house drops to 20-30%, which is obviously getting into the danger zone. Only in the super-cold spells for a week here or there does it go as low as 10-15%.

I don't have air-conditioning, which would dry the air out in the hot Summer months.
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Re: Flute Shrinkage in Dry Weather

Post by tstermitz »

I'm not necessarily in favor of humidifying the whole house or even a single room.

Humidity condenses on the coolest surface in the house. In my case that would be the basement walls behind the insulation. Due to a lack of a vapor barrier (mister handyman's renovation), the insulation starts to pick up extra moisture leading to mold.

It depends on your house, but I you can imagine other issues with excess humidity.
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Re: Flute Shrinkage in Dry Weather

Post by tstermitz »

I can testify that the joints on my new (10 year old) flute became tighter upon arrival in my house during the past couple of low-humidity weeks, despite lots of daily playing. After putting it in the humidifier plastic box (50%) for a few days, the joints loosened.

Before putting it away, I always swab the flute so it is merely damp rather than dripping.

Flute from a reputable modern maker, Blackwood with silver rings and threaded joints.
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Re: Flute Shrinkage in Dry Weather

Post by busterbill »

I am just curious. This may not be the case, but if you look carefully when your joints feel tight, are they still completely round? You may need to test this with a caliper. I have seen at least one flute made by a major maker whose wood shrunk to a slight oval when it dried out. That would make the joints feel tight even if the wood has shrunk.

Again, this may not be the case with your flute, but it may be worth taking a look. It is subtle.

If you live in Colorado you may be in a house that has been built in the last 50 years with the idea of being "tight" for insulation purposes. Depending on the year your house was built it may be more prone to mold with humidification. The technology advanced over the years of decrease the mold potential and improve air flow, but it has been an evolving science.

In my century old Chicago house the idea of being air tight is a bit of a joke even with my best efforts so mold is not as much of an issue. But humidifying a room in a tight house is possible if air flow is increased.

I've had interesting experiences with flutes kept in a humidified room and cupboard. When I take them out to the non-humidified world for a few hours of playing they still can show the effects of the external humidity change. My only defense in this case is to make sure my flute is properly oiled. Your flute stored in a well humidified case may be experiencing the same minor shocks when you take it out and play it in a dry room. Playing will give you moisture on the inside, but do nothing for the outside surface.

So watch your instrument carefully if you are experiencing movement in the wood. Oiling may help.
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Re: Flute Shrinkage in Dry Weather

Post by Conical bore »

busterbill wrote:I've had interesting experiences with flutes kept in a humidified room and cupboard. When I take them out to the non-humidified world for a few hours of playing they still can show the effects of the external humidity change. My only defense in this case is to make sure my flute is properly oiled. Your flute stored in a well humidified case may be experiencing the same minor shocks when you take it out and play it in a dry room. Playing will give you moisture on the inside, but do nothing for the outside surface.
Here's another idea in addition to oiling the barrel: Wax the outside of the flute as well.

About once a week in the Winter months, I apply a very small amount of cork grease to the outside of the flute, then wipe it off with a soft cloth, leaving a very thin layer. I started doing that with my Windward flute because the maker recommends it in the flute care instructions, and now it's part of the regular maintenance routine on my current Aebi flute. I just use one of those little tubes of cork grease (wax) from a local music store. Beeswax with a little mineral oil to soften would work too.

Aside from aesthetics and keeping the flute clean, the wax helps protect the outer layer from drying out too quickly when I move the flute into a dry air environment for playing in a session. It also protects the area around the embouchure hole that tends to dry out and get that matte-surface look from mouth contact, especially if you drink alcoholic beverages in session (raises hand). There is enough residual wax on the head joint that I can just use my thumb to rub a little over onto the embouchure area when I put the flute away.

Anyway, I'm not 100% sure how much this outer wax treatment helps with humidity changes, but it can't hurt, as long as you keep it away from the pads and hole seating areas on a keyed flute. And it makes the flute nice and shiny. :)
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