what humidity and how do you keep it?

[Jayhawk]

Gary - feeling a bit tetchy, eh?

While you may be making some good points (although wooden bridges in my area do not have expansion joints, neither did my grandfather's 100 year old wooden barn, nor the old log cabin on his property dating back to the mid 1800s), it is much easier to deconstruct another's theory or poke holes in the methods of what Terry has done than to actually do any research yourself. Terry has done more than any other flute maker that I am aware of to try and experiment with some of these cherished beliefs about wooden flutes.

Since you're obviously knowledgable about woodworking, why don't you do the scientific thing and try to replicate (or disprove) what he has done? After all, the scientific method should be about replication and verification rather than simply arguing someone who has actually taken the time to try and investigate these things is wrong just because you think so.

Eric

[sturob]

Well, yeah, it is a lot easier to poke holes in another's theories, as anyone who's read MY posts can tell you.

I have the utmost respect for Terry and the work he's done for our instrument and his craft. But . . . Gary does point out why Terry's evidence is anecdotal at best.

We're left with the fact that we don't really know what causes these instruments to crack. Moisture/humidity, dHumidity/dTime, temperature, dTemperature/dTime . . . all things we could look at.

It'd be really easy to construct a good experiment.

Stuart

[Terry McGee]

Hmmm, I can see from GarryKelly's intemperate and holwer-filled response (above) that I'm not going to be able to convince him that humidity not temperature is the enemy. So let's see what others have to say.

A concise and easily understandable introduction to the topic from a PhD in wood science, published by the University of Massachusetts:

http://www.umass.edu/bmatwt/publication ... ntent.html

And a discussion on the topic as it relates to another musical instrument, the harpsichord:

http://www.hubharp.com/technical_articl ... midity.htm

Another from the Piano Guild:

http://www.ptg.org/ptgtb3.htm

A stunning "left-brain lutherie" paper on ukeleles:

http://www.ukuleles.com/Technology/humidmath.html

A fascinating future-look in the report of a Finnish conference on Healthy Buildings, in which wood based materials are being considered as humidity banks and regulators for the benefit of the people in them. Remember what I was saying about humidify your wooden case too as it will continue to provide a humid environment for the flute inside while away from home. These people are thinking somewhat bigger!

http://www.hb2000.org/workshop10.html

And there's heaps more on the 'net - search on "temperature and humidity effects on wood". Or just consult any decent book on furniture making.

Now here's GarryKelly's big chance to convince us of the merit of his hypothesis. I can demonstrate easily and repeatedly a change of around 0.4mm in the diameter of a head by subjecting it to a 30% change in relative humidity. I conclude that shrinkage around the immoveable metal is the case for cracking. GarryKelly insists that the cracking is caused by expansion of the metal due to increase in temperature. Let him (or anyone else but me) calculate the change in temperature required to expand a 20mm brass tube by 0.4mm. All you need is the coefficient of linear expansion of brass - you can get that off the 'net by searching on those terms. I'd do the calculation myself, but might be accused of rigging the figures.

Terry

[meemtp]

Here's an example to support the validity of what Terry says. Violins, though of different construction than flutes ie-top plate, belly sides, ribs etc. Will certainly demonstrate dimensional changes if humidity is altered. Tops shrink (and may crack), soundposts can shrink and fall, seams can open etc. This is all because the wood shrinks or swells based on its mositure level. Just like flutes! Good enough for me. This is seasoned wood too, but it still changes moisture content unless it is seasoned, built and owned for it's life in the same place. Some violins even require winter and summer bridges and/or soundposts. It's not due to the different temps, as inside performing temps are not that different, it's because the dimensions of the fiddle end up changing due to shrinkage. And these instruments are not having moisture put inside them when playing then drying afterward. Think of how much more they'd change!

[Terry McGee]

Here's an example to support the validity of what Terry says. Violins, though of different construction than flutes ie-top plate, belly sides, ribs etc. Will certainly demonstrate dimensional changes if humidity is altered. Tops shrink (and may crack), soundposts can shrink and fall, seams can open etc. This is all because the wood shrinks or swells based on its mositure level. Just like flutes! Good enough for me. This is seasoned wood too, but it still changes moisture content unless it is seasoned, built and owned for it's life in the same place. Some violins even require winter and summer bridges and/or soundposts. It's not due to the different temps, as inside performing temps are not that different, it's because the dimensions of the fiddle end up changing due to shrinkage. And these instruments are not having moisture put inside them when playing then drying afterward. Think of how much more they'd change!

Yea, verily, meept. Indeed I've been discussing this matter with a fiddle repairer who works in New Mexico (yes I know - some people like to take on extra challenges in their lives!). He confirms that not only do fiddles (mostly made in more sympathetic climes) suffer a lot in the body there, but the humidity is so low that even the ebony tuning pegs (also made elsewhere) go significantly out of round and become snatchy.

Terry

[andrewK]

Ah, the going out of round.
Is not half of the trouble with the flute shrinking on the headtube and perhaps cracking (in line perhaps with your barrel crack) that the bore has become oval not just from shrinkage but from it's way of distorting. Especially boxwood?

[GaryKelly]

It's not tetchiness, nor am I 'holwering intemperately' as Terry would suggest. I'm just appalled when anyone makes a claim for "scientific proof" by announcing the results of a bunch of completely un-scientific Heath-Robinson one-off trials, without any scientific method or any description of the apparatus used. And then refuses to answer even the most basic questions about the experiments.

It's very easy to deride me, ignore my questions, pooh-pooh fundamental physics, and sweep away all the points I've made. All you need to do is announce "Hmm, not going to convince him, he's howling intemperately folks!". But then comes the ultimate in 'non-science': "Let him (or anyone else but me)" prove to the majority that they're right because I'm going ignore anything that might suggest I'm wrong and I'm certainly not going to do any research into the coefficient of expansion of brass.

Yes, it's easy to poke holes in other people's theories, particularly when fundamental physics and engineering are the pointy sticks you use to do the poking. We've already seen how people confuse humidity with annual rainfall, for example. But for all the reasons quoted in my post about the miserably flawed 'scientific experiments' Terry's conducted, they're still miserably flawed, and Terry still hasn't, for example, answered the question I've asked of him (twice) about keeping the test environment temperature constant.

No-one can replicate his experiment, Jayhawk. We know nothing about the aparatus he's using or the conditions of his trial. For some reason he won't tell us.

For example, make a flute from blackwood that's been sitting around turned round and pilot bored in Canberra's average 45-50% humidity for some years , then bring it down to 20%.

Bring it down to 20%? How? For all we know he's blasting the thing with an electric hairdryer, baking it in a kiln, or sticking it in a tupperware box filled with Silica Gel dessicant sachets!

Go back and re-read my "holwer-filled" post. Tell me what the holwers are. Tell me where I'm wrong. Jayhawk's at least taken the trouble to read it, but his post in fact supports everything I've said. The hundred-year-old bridges and barns wouldn't be there if seasoned wood lost water and shrank at the incredible rate Terry claims. There'd be nothing left but a dessicated husk a few centimetres long. There'd be no thriving antique furniture market because those fine extant Louis XV chairs and Victorian bureaux would've imploded. All that fine marquetry, all the wonderful inlays of different woods would've shattered and evaporated. They haven't. And they see the same humidity changes as anything else, and have done for longer than a flute made "some years" ago. I have a pair of antique flintlock pistols at home that are the best part of 130 years old. The walnut handles still fit, the locks still fit, so do the screws. But according to Terry's "scientific" experiment, they should've withered away like Dracula in sunlight about 120 years ago.

Then, to cap it all, Terry says:

And ignore the effect of the breath during playing. In a lined flute, it is well insulated from the wood of head and barrel by the liner (why does no-one acknowledge this?). Even in a non-lined flute or in non-lined parts of flutes, the density of the timber and the presence of oil slow the uptake.

From which we are obliged to deduce that humidity and moisture doesn't matter a jot when it suits him to say so, but by God your flute will shrink and crack after only "3 or 4 days" at RH 20%, even if the density of the wood and the presence of oil slow the air's uptake of moisture from the wood (moisture that you have to ignore when you put it in, that is).

And let's not forget:

I still argue that the old fully lined head and barrel idea has long passed its use-by date. My "New Improved Tuning Slide" (partial slides with cork buffers at the wood-metal interface) is one solution, and is available to other makers at no cost. (http://www.mcgee-flutes.com/fluteslide.html)

Know what that cork lapping is? An expansion joint. Know what else it is? Vested interest.

Is it not also strange that someone who clearly believes that 'wood shrinks but metal doesn't' causes cracks, but refuses to accept "metal expands but wood doesn't."

Although to be fair Terry covers all the bases by conceding:

...every lined head or barrel is under stress and is just awaiting an excuse to crack, then it is consistent to believe that the final straw might come in the form of a sudden warming of the tube

Making good flutes is one thing. Passing off hearsay and one-off observations as "scientific proof" is quite another.

Dunno about brass, but a sterling silver cylinder of diameter 26mm and length 400mm will, if my maths is as good as it was 30 years ago, increase its surface area by 10.12 sq.mm with a 30 deg.F increase in temperature.

Of course my maths is a bit ropey these days. I don't know the Young's Modulus for African Blackwood, and it'll take a structural engineer to calculate the bursting pressure of a headjoint and the amount of pressure exerted by the tuning slide liner. Not to mention stress and failure-mode analyses by real scientists. The problem is, it'll require destructive testing and a large batch of samples. Who can afford that?

But as Terry also concedes on his website:

While the maker no doubt put a lot of effort into smoothing the junction between wood and metal at the bottom of the embouchure chimney, differential expansion rates can mean that the metal juts into the airstream,"

So even he acknowledges there's significant expansion of the liner when it warms up faster than the wood surrounding it, enough for it to jut into the airstream. Confusing, all this contradiction, huh? Or is that an intemperate howler too?

[andrewK]

I can't be bothered in my condition with co-efficients of expansion but I shall ask Mr Wilkes if he will lend me a silver head tube which I can put in a deepfreeze somewhere at - 30 C, measure with my micrometer ( whilst wearing gloves, then take to a warm room and re-measure it after an hour or two !
Given that all the expansion will bear on the lines of contact formed by the oval head / barrel tubes ( and one will give way before the other - usuallt the one weakened by the mouth hole )
Perhaps Graham Farr, ( being a first class structural engineer ) will already know the increase in diameter of a silver tube of 19 mm or so when heated 100 degrees C.
Come to think of it I could take some icy water, put the tube in and bring to the boil !!!
Then I could have a cup of tea and contemplate the result.

[jim stone]

It's not tetchiness, nor am I 'holwering intemperately' as Terry would suggest. I'm just appalled when anyone makes a claim for "scientific proof" by announcing the results of a bunch of completely un-scientific Heath-Robinson one-off trials, without any scientific method or any description of the apparatus used. And then refuses to answer even the most basic questions about the experiments.

It's very easy to deride me, ignore my questions, pooh-pooh fundamental physics, and sweep away all the points I've made. All you need to do is announce "Hmm, not going to convince him, he's howling intemperately folks!". But then comes the ultimate in 'non-science': "Let him (or anyone else but me)" prove to the majority that they're right because I'm going ignore anything that might suggest I'm wrong and I'm certainly not going to do any research into the coefficient of expansion of brass.

Yes, it's easy to poke holes in other people's theories, particularly when fundamental physics and engineering are the pointy sticks you use to do the poking. We've already seen how people confuse humidity with annual rainfall, for example. But for all the reasons quoted in my post about the miserably flawed 'scientific experiments' Terry's conducted, they're still miserably flawed, and Terry still hasn't, for example, answered the question I've asked of him (twice) about keeping the test environment temperature constant.

No-one can replicate his experiment, Jayhawk. We know nothing about the aparatus he's using or the conditions of his trial. For some reason he won't tell us.

For example, make a flute from blackwood that's been sitting around turned round and pilot bored in Canberra's average 45-50% humidity for some years , then bring it down to 20%.

Bring it down to 20%? How? For all we know he's blasting the thing with an electric hairdryer, baking it in a kiln, or sticking it in a tupperware box filled with Silica Gel dessicant sachets!

Go back and re-read my "holwer-filled" post. Tell me what the holwers are. Tell me where I'm wrong. Jayhawk's at least taken the trouble to read it, but his post in fact supports everything I've said. The hundred-year-old bridges and barns wouldn't be there if seasoned wood lost water and shrank at the incredible rate Terry claims. There'd be nothing left but a dessicated husk a few centimetres long. There'd be no thriving antique furniture market because those fine extant Louis XV chairs and Victorian bureaux would've imploded. All that fine marquetry, all the wonderful inlays of different woods would've shattered and evaporated. They haven't. And they see the same humidity changes as anything else, and have done for longer than a flute made "some years" ago. I have a pair of antique flintlock pistols at home that are the best part of 130 years old. The walnut handles still fit, the locks still fit, so do the screws. But according to Terry's "scientific" experiment, they should've withered away like Dracula in sunlight about 120 years ago.

Then, to cap it all, Terry says:

And ignore the effect of the breath during playing. In a lined flute, it is well insulated from the wood of head and barrel by the liner (why does no-one acknowledge this?). Even in a non-lined flute or in non-lined parts of flutes, the density of the timber and the presence of oil slow the uptake.

From which we are obliged to deduce that humidity and moisture doesn't matter a jot when it suits him to say so, but by God your flute will shrink and crack after only "3 or 4 days" at RH 20%, even if the density of the wood and the presence of oil slow the air's uptake of moisture from the wood (moisture that you have to ignore when you put it in, that is).

And let's not forget:

I still argue that the old fully lined head and barrel idea has long passed its use-by date. My "New Improved Tuning Slide" (partial slides with cork buffers at the wood-metal interface) is one solution, and is available to other makers at no cost. (http://www.mcgee-flutes.com/fluteslide.html)

Know what that cork lapping is? An expansion joint. Know what else it is? Vested interest.

Is it not also strange that someone who clearly believes that 'wood shrinks but metal doesn't' causes cracks, but refuses to accept "metal expands but wood doesn't."

Although to be fair Terry covers all the bases by conceding:

...every lined head or barrel is under stress and is just awaiting an excuse to crack, then it is consistent to believe that the final straw might come in the form of a sudden warming of the tube

Making good flutes is one thing. Passing off hearsay and one-off observations as "scientific proof" is quite another.

Dunno about brass, but a sterling silver cylinder of diameter 26mm and length 400mm will, if my maths is as good as it was 30 years ago, increase its surface area by 10.12 sq.mm with a 30 deg.F increase in temperature.

Of course my maths is a bit ropey these days. I don't know the Young's Modulus for African Blackwood, and it'll take a structural engineer to calculate the bursting pressure of a headjoint and the amount of pressure exerted by the tuning slide liner. Not to mention stress and failure-mode analyses by real scientists. The problem is, it'll require destructive testing and a large batch of samples. Who can afford that?

But as Terry also concedes on his website:

While the maker no doubt put a lot of effort into smoothing the junction between wood and metal at the bottom of the embouchure chimney, differential expansion rates can mean that the metal juts into the airstream,"

So even he acknowledges there's significant expansion of the liner when it warms up faster than the wood surrounding it, enough for it to jut into the airstream. Confusing, all this contradiction, huh? Or is that an intemperate howler too?

If you are appalled by unscientific claims being made
on a message board on flutes, you will not get through
the day mentally intact--given so much of what's
going on in the world. Better to be appalled by
the Holocaust and cordially controversial here.

It's prudent to save being appalled for the
big stuff, IMO. It isn't as though you won't get
enough exercise.

You're saying lots of intelligent things, and if you
will just ratchet it down a bit this could be
a helpful and interesting conversation.

[andrewK]

With my feeble calculating I get the increase in tube diameter to only about 0.12 mm which doesn't sound very much. Have I got this right ?

This does seem an interesting thread. It is time some more analysis is made of all these damn cracks. Especially when folks find them appearing ( like the ones reported by sledgehammer ) in the head and barrel overnight.
It is too common a problem not to get to the bottom of .
No doubt the more restrained ( less heated ) the discussion is the nearer we shall get to th " Truth "

[BMFW]

Perhaps Graham Farr, ( being a first class structural engineer ) will already know the increase in diameter of a silver tube of 19 mm or so when heated 100 degrees C.

Hmmm, my branch of structural engineering is on a somewhat different scale, being to do with building design! I could tell you that a wooden flute would not make a satisfactory floor joist but that wouldn't really get us anywhere.

However, it appears as is the Coefficient of Thermal Expansion for silver (Oh my God, I can't believe I'm getting into this) is 0.00002 mm/mm/degree C or 0.0000109mm/mm/degree F. Given a 19mm diameter tube, and an increase in temperature of 30 degrees F (the figure mentioned by Gary), the increase in circumference would be 0.0195mm with a resulting increase in diameter of 0.006mm, to 19.006mm or 0.03%. (or as we say in this part of the world "a ba' hair")

Now, I have no idea if this supports or otherwise, either the theories we have heard. I equally have no idea whather my maths or logic is deeply flawed. If either my maths or logic are flawed, then I will be happy to provide everyone with a list of buildings that I have designed in order that you may avoid them!

Graham

[andrewK]

But the increase complained of is from - 30 Centigrade to American room temperature .
Say 100 centigrade degrees altogether.
Graham ?

[BMFW]

At 100 degrees C increase, I get a 0.11938mm increase in circumference, 0.037917mm increase in diameter, 0.2%.

[sturob]

-30°C to American room temp is only about 50 Celsius degrees . . . "room temp" is 68°F, which is 20°C.

Stuart

[Cathy Wilde]

Just wanted to log in and apologize for getting 'tetchy' myself Friday. It's been an exhausting couple of weeks at work, and as one of my complaints has long been that RH and temp. etc. ARE issues that many of us don't think/talk about enough, I got a wee bit wound up.

So my apologies to Gary and Stu in particular. Obviously this thing is a burr under my saddle blanket , but I appreciate your illuminations and corrections.

And although I have no science to support it, FWIW the one flute I have that seems the most stable, adaptable, and consistent player throughout temp and humidity change is the one made by Mr. McGee. So I for one really appreciate and TOTALLY encourage his experiments and thoughts on this subject!

Love from the House of Winter Thermostat Setting = 68F and avg. 42% RH (at least yesterday and today),

cat.