what humidity and how do you keep it?

[Jayhawk]

I'm still searching for the answer to "is wood hydroscorpic" since my question about wooden floor boards shrinking in low RH in winter and doors swelling was unanswered. Looking to museums who have a bit of experience in wood preservation I found this:

http://www.hfmgv.org/explore/artifacts/furniture.asp

The above is less scientific than the following:

http://alcor.concordia.ca/~raojw/crd/re ... 01180.html

Here's two more:

http://www.durable-wood.com/moisture/index.php
http://www.umass.edu/bmatwt/publication ... ntent.html

So, while I do agree with those saying temperature is a factor, wood IS hydroscorpic and RH does have an impact on the moisture content of the wood with prolonger exposure.

This topic is starting to remind me of the nature vs. nurture debate...but it's still interesting.

Eric

PS - I still blame the Burrs, including Aaron...

[GaryKelly]

Sorry Eric, I wasn't ignoring you, I followed your instructions and stopped reading your post... having re-read it, I'd say the flooring issue is likely a combination of temperature, humidity (over a prolonged period ), and the wood itself (plus the possibility of damp too).

More tomorrow, for I am digesting EMC. Some interesting building regulations in Australia concerning floorboards, of all things.

I blame the burrs too, Raymond has a lot to answer for.

[Jayhawk]

Gary,

this whole topic has been incredibly interesting in my opinion. Lots of new knowledge about wood, stress, temperature and RH to digest. And I'm sure your right, Raymond is probably involved in some way...

Eric

[Berti66]

it's a fact that when you have slightly wobbly joints and you put the flute in a humidor (of any sort) with the proper RH, that the wobbliness will disappear after a few days....
doesn't that proof that wood is hygroscopic.

or am I saying something stupid now?
berti

[bang]

is it possible that burrs, etc, were intended as a *solution* to problems of wood/metal expansion & contraction? they would seem to allow some room for wood/metal to move w/out the slide falling out. perhaps the wood was bored slightly larger than the metal slide, held in by the burrs, but w/ some wiggle room to prevent cracks as temp/humidity varied?

does wood shrink (&/or warp) over long periods of time regardless of humidity & temperature? is there some long term process by which wood becomes more brittle & subject to cracking?

enjoy! /dan

[Terry McGee]

Well, I haven't had time to delve into EMC as deeply as I would like but I will say this: Everything I've read so far on the subject indicates this:

1. EMC is valuable when considering the storage of lumber out of doors.
2. EMC takes weeks or months to make itself felt.

I concede I have more reading to do, but at first glance the fact that it could take weeks or months for the moisture content of wood to 'stabilise' certainly rules out EMC effects in a flute that cracks overnight. In my opinion! As I said, I have more reading on the subject to do.

I'll concede that I was surprised to see stabilising times of only 4 days drying and 7 days relaxing, but we have to remember we're talking timber that's only 4mm thick, but with lots of surface area, so that the transfer can proceed quickly. Also that is un-oiled timber, I haven't tried an oiled piece yet. It would be nice to believe it will make a difference!

But remember we don't have to achieve this shrinkage overnight. The shringage has the whole dry season to develop. The question has to be whether we can get to the end of a nother dry season without the flute cracking.

Oh, and to finally (hopefully) lay to rest the UK versus India argument where humidity is concerned. Have a look here:

http://www.bbc.co.uk/weather/world/city ... shtml?list

Where you can see the "average" annual humidity from cities all around the world. The really big difference between Delhi and London, say, is not humidity, but temperature. And an even bigger day/night temperature differential.

Now you have to consider that India is a very big country with vast climatic differences. The coastal regions are very humid, but parts of the inland are very dry. Hyderabad caught my eye, with humidity ranging from 27 to 81%, compared to London's 56 to 87%. And that's outdoor!

We know Hyderabad is relevant to our discussion as His Highness, the Nizar of Hyderabad is listed 5 times in the Boosey & Co sales records! There are many more entries for the various Hyderabad infantries.

Incidentally, ebonite was brought into use for flutes for India, and Booseys made thousands of them. Clinton went as far as making a conical flute in metal for use in India. To see this extradinary device, see:

http://www.mcgee-flutes.com/clint-India.htm

Terry

[Terry McGee]

is it possible that burrs, etc, were intended as a *solution* to problems of wood/metal expansion & contraction? they would seem to allow some room for wood/metal to move w/out the slide falling out. perhaps the wood was bored slightly larger than the metal slide, held in by the burrs, but w/ some wiggle room to prevent cracks as temp/humidity varied?

They couldn't afford much "wiggle room" as the gap between outside of liner and inside of wood does have to remain airtight. But I think the burrs and scratches were probably intended as ways to reduce the necessary tightness of fit. It's sad to think that in doing so they might have become the cause of extra problems. But then, maybe if they had done without the burrs and made the wood a tighter fit, they would have cracked even earlier. Who knows?

does wood shrink (&/or warp) over long periods of time regardless of humidity & temperature?

Quite possibly, but of course it's unuual to be in the absence of continual change in temperature and RH, so it would have to be a rigorous experiment to find out! But I do expect to see some cumulative effect of humidity cycling, which is something that goes on every day.

is there some long term process by which wood becomes more brittle & subject to cracking?

I believe that dry wood is more brittle and prone to cracking compared to moist wood. I haven't researched this though. (There was probably some stuff about it on those various URLs I gave earlier.) If it is the case, it would certainly contribute to cracking of lined flutes - the same dryness that shrinks the wood is also reducing its ability to withstand the stresses. Double jeopardy! To a certain extent we don't need to know the fine details of what happens around the cracking point - we just need to know not to go there!

Terry

[Denny]

from a fire wood perspective there are some woods that I cut into rounds and let dry a year or two before splitting. It is too much work to split before it dries.

[Terry McGee]

from a fire wood perspective there are some woods that I cut into rounds and let dry a year or two before splitting. It is too much work to split before it dries.

Indeed, let Mother Nature do most of the work! Firewood is a good example of what can happen in the unlined section of your flute (including the head if unlined) if you don't mop it out after playing. The outside of the wood is dry and shrunken, the inside is wet and swollen, and something has to give. Always mop out, unless you want your flute to turn into firewood. Seriously. I've seen the middle section of an 1860's cocuswood flute errupt in cracks because the owner was not in the habit of mopping out. He is now!

The firewood example shows us why dense timbers used in flutemaking cannot be seasoned in the log - loss through splitting would be terrible. They are cut up "green" into the squares needed - about 1.5" square is large enough for a keyed D flute. The ends are waxed to prevent too rapid loss of moisture through the end grain which might cause end-splitting (remember how the firewood allways splits at the ends first) - in that form they are safe to travel, store and season. I prefer to turn them round as soon as I can after they get here, as this removes unneeded wood and improves air flow through the piles of timber. I also bore them out, as again it removes timber I don't use, and provides air access to the inside of the piece. Removing the unnecessary wood and drying from both inside and outside at the same time substantially reduces stresses and the time it takes to reach equilibrium with the workshop air. I store the wood in the wire drawers sold for bedroom wardrobes - they provide brilliant ventilation. I monitor the weight of a test piece in each consignment to know when equilibrium has been reached. See "new supplies" and "storage" at http://www.mcgee-flutes.com/making.html to see what raw flutes look like in these various stages.

Terry

[andrewK]

Surely the flutewood hardens and I imagine perhaps shrinks as it seasons over a few decades as the hemi-celluloses I mentioned before oxidise to celluloses ?
This shrinkage probably contributes to disasters 150 years down the line.

[Terry McGee]

Surely the flutewood hardens and I imagine perhaps shrinks as it seasons over a few decades as the hemi-celluloses I mentioned before oxidise to celluloses ?
This shrinkage probably contributes to disasters 150 years down the line.

Definitely outside my range of expertise once we get into organic chemistry. What can you tell us about this process? What does it need to make it happen - just exposure to air? And is it a surface effect or likely to happen throughout the piece?

Terry

[andrewK]

It has been considered important in the violin making field. The nature of the maple changes over the decades, changing how it cuts and stabilises.
Just exposure to air.
Of course, up to a time the longer the more complete the change.This is the real seasoning. Not drying, which can be " faked " quickly with varying degrees of success.I suspect that this accounts for the splitting differences between new & old work, the old makers' having had more mature wood available.
I recently bought some long pieces of oldish ( 45 year ? ) blackwood which rings particularly well - like cocus.
Turned, but not bored out for some silly reason. Big shame !
I am awaiting a delivery of cocus from the US of A which I hope will ring like old blackwood !!
I came across an analysis a couple of years ago , though, of a Strad Belly ( pine ) which he had used almost new !.
Congratulations to Terry in his new career.
Hope he long contiues on this thread.
And of course to Garry as his Svengali !
No doubt Loren will fill us all in.
At least fill us in about how old wood is different to work.
Hope he doesn't shout at us !

[meemtp]

A number of modern violin makers are using humidity chambers for their tonewood. I think this is part of the trend of modern makers, small and large, trying to speed up the "opening" up process. A poor attempt at this is some making tops thinner than the old makers in order to have more vibration with less break in time. A good handmade violin can take years for its sound to mature and everyone wants their new fiddles to sound old right away. On a side note, some of the most prized violin tonewood is maple that had been sitting on the bottom of the Great Lakes for 100 years or more. Supposedly its acoustic qualities are quite superior. But, apples and oranges as fiddles don't have moisture reintroduced into the wood in the way flutes do.

[andrewK]

No Meemtp.
The question is WHAT wood are we talking about and how much has it shrunk / stabillised.
Whether the oxidised wood is not going to perform the same as the " fresh wood " in taking up water, and whether it will shrink less over the century being arguably harder and of a better texture.
Whether an old piece of wood is going to open up when it crosses the Atlantic. Not every maker has much experience of his head joints cracking, and this may be down to the use by some of 15 + year old wood. which may ( inter alia ) have sorted itself out !
The reason for makers not using old wood, whether for flutes or violins is expense & availability.
( Though I am often shocked at the very high quality of wood used in their low cost handmade output by the Chinese! Pity they have to kill off the ladies working in the varnishing rooms for a pittance ! World trade ! ).
The cocus I recently mentioned awaiting from remote regions ( USA) is coming by a slow boat ( to keep the cost down, but also to minimise the risk of aerial damage ). Iraqi missiles, splits ?

[Terry McGee]

This is the real seasoning.

Yes, the word needs some close attention, doesn't it. Nothing to do with the Colonel's favourite blend of herbs and spices. And not much to do with drying. When we get our wood, it still has a lot of the moisture in it from its days as a tree. Dense woods don't kiln dry well, so we air dry them. That brings them down to be in equilibrium with the Relative Humidity of the storage atmosphere. But that's not seasoning, it's drying. Seasoning occurs over the next number of years, as the timber's moisture content is cycled up and down by the annual cycle of wet & dry seasons. Seasons, get it - "seasoning". But timber "well seasoned" at Canberra's 50% or London's 70% has never even reached Hyderabad's 27% or whatever a long dry spell in New Mexico can throw at us. So not even visiting, let alone seasoning.

Hmmm, I wonder what the average RH of Sailkot in Pakistan is. That's where at least some of the dreaded Pakistani flutes eminate from.

Congratulations to Terry in his new career.
Hope he long contiues on this thread.
And of course to Garry as his Svengali !

Eek, Svengali? What does that make me? Surely not Ms Trilby? And you Andrew, not Gecko?

(Geckos (small lizards) slip in and out of my workshop from time to time.)

Terry