WTT: Workshop temperature question ...

Whistle
1

I’d been assuming I will need to set up my lathe in the basement so the winter temperatures won’t be a factor in working wooden whistles.

Then I noticed mention that Pat O’Riordan makes his whistles in his garage, so I thought I’d better double check.

Of course, he might have a heated garage, but it would be more convenient for me and less of an imposition on my household if I were to set up my lathe in the same space as the rest of my woodworking machinery, which is a small barn that’s been outfitted with doors so it could be used as a two car garage (with a hayloft and milking stalls).

However, it does get cold in the winter. What would happen if I were to work a batch of wooden whistles in the cold?

Thanks in advance for your help.

Best wishes,
Jerry

2

The one problem I see is that cold air is dry air – how cold DOES your garage get? If it’s in the see-your-breath range, I can see dryness being a problem. Of course, I’ve never made a wooden whistle, but maybe Paul or Davey will chime in.

3

Hi, Chas.

Actually, I believe you’re mistaken about that.

Cold air isn’t inherently dry. HEATED cold air is.

Relative humidity is a function of the percentage of moisture that air of a given temperature is capable of holding.

If you take outdoor air, let’s say at 60% relative humidity and 25 degrees fahrenheit, and then heat it to 72 degrees fahrenheit, the relative humidity goes way down, which is why we get dry skin and the doors close so easily in the winter when the furnace is on.

This is interesting from an historical perspective, because some of the exquisite antique furniture that was built before central heating was invented, was not constructed to allow for the seasonal moisture cycle that alternately shrinks and swells the wood, which is an artifact of central heating. Cross-grain construction, which is taboo in a climate where there’s cyclic artificial heating of the air, is no problem in the tropics, where there are no furnaces.

Bringing a whistle from the unheated shop in the winter, into a heated environment in a house will be bringing it from a more moderate humidity to a dry humidity, which might be a factor. However, I’m inclined to be more concerned that the temperature difference may be problematic than the humidity difference.

In any case, I’m looking for all available information that’s relevant to this, whether it’s regarding temperature, humidity, phases of the moon, or whatever.

Best wishes,
Jerry

P.S. I do appreciate your helping to think aloud about this, so please don’t hesitate to theorize about such things, even if I or someone else may chime in with differing information.

4

Terry McGee has done some experiments on the effects of cold and heat on flutes: http://www.mcgee-flutes.com/temps.html. He basically says that it doesn’t hurt as much as we tend to think. Are you on the flutemakers mailing list: http://groups.yahoo.com/group/flutemakers/?

Are you planning to keep the wood out there as well, or just carrying it there, working on it on the lathe, and taking it back to a kinder climate? In this case, I’d guess that you will be a lot more uncomfortable than the wood, working with the metal tools with bare hands. Isn’t it rather cool in the winter where you live?

As an aside, there’s no cosier place in winter that a heated instrument makers workshop.

Sonja

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Thanks, Sonja.

That’s very helpful.

Best wishes,
Jerry

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Jerry, the first thing that comes to mind to me is the tuning. Are you planning to do the tuning in this colder temperature? I tune my instruments calibrated to 70 deg. F for a good all around temperature. There is quite a difference tuning when you vary from this temperature (for every 10 deg of variation one needs to adjust by 4 cps). So if you are tuning at 50 deg. F you would need to set the calibration at A=432 cps)
Have you figired this in to your calculations?

Ronaldo

7

Actually, it really IS drier. The RELATIVE humidity isn’t lower, but the ABSOLUTE humidity, that is, the concentration of water vapor in ppm, is much lower. (The dewpoint is a measure of absolute humidity.) The reason that the relative humidity indoors in the winter is lower is that the outdoor air sucks moisture from the indoors. If it’s 40F outside with 50% RH, if it’s 70F indoors, with the same amount of moisture in the air, the RH indoors is about 15-20%. In my house, the RH tends to hover around 40%when the average outdoor temp is 30-40F, so there’s actually more moisture indoors than out.

The reason that the absolute humidity is important is because the wood will tend to equilibrate its moisture content with that of its environment. I have no idea on what time scale this happens, though; it probably happens much more slowly in the winter because the vapor pressure of the water near the wood surface is lower, but it will evantually really dry out. Heck, it might help you age your roughturned whistles more quickly.

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Thanks, Ronaldo.

That settles it. The lathe will live in the basement.

Best wishes,
Jerry

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Good idea Jerry!!

Ronaldo

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No, nothing is sucked outdoors. Warm air has more capacity to retain moisture than cold air, so cold winter air is drier. We open windows and doors and let it in, it heats up and then the wood starts giving away moisture to the air that isn’t saturated any more, because it is warmer now.

I think we all mean the same, it is a common problem, and instrument wood doesn’t like it at all.

Sonja

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Chas, I think the answer is, we’re both right.

Wood reacts to the moisture in the air based on relative, not absolute humidity, so it doesn’t dry out in the cold. Even though there’s a lot less H2O held by cold air, the air isn’t capable of holding much more H2O than is already in it, so it doesn’t dry out the wood.

Conversely, if you bring the wood into a room where that outdoor air’s been heated and people have been living (e.g. breathing), there’s a lot more H2O in the air than outside, but the relative humidity is much lower because the furnace’s on. Even though there’s more H2O in the air, compared to outside, that indoor air will take moisture out of the wood and reduce its moisture content because the RELATIVE humidity of that air is lower than the relative humidity of the outside air.

It’s not a question of how much H2O is in the air in absolute terms; it’s how much H2O the air can hold that’s critical in determining whether it raises or lowers the moisture content of the wood.

In other words, the heated, indoor air can hold more H2O, so it will dry out the wood, and the cold, unheated, outdoor air can hold less H2O, so it won’t dry out the wood.

Best wishes,
Jerry

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You’re too polite.

Credit where credit is due. It’s your idea. You’re the one with the experience in these matters.

Thanks again,
Jerry

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i think you made the right choice for the basement. also, i like to keep my wood stored where the finished product will be used. i keep my wood stacked under the bed and couch, the big pile in the basement. i bring up more wood to the upstairs about 2 months before i use it. i think it makes a positive difference in shrinkage and checking.
the room where my instuments live is a constant 60-65% humidity.
just some thougths :slight_smile:
tansy

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Um, nope, it doesn’t get dryer because it’s warmer, it was already dry. Relative humidity only measure how much moisture the air can hold, not how much is actually in it. If you don’t think the cold air can pull the moisture out of your wooden whistle, well, throw some food in your freezer without wrapping it, then tell me if you’ve changed your mind in a couple of weeks. :slight_smile:

Some friends of mine are from Alaska. The stories they tell of issues with static electricity because of the dry air are just too funny for words. In Alaska, static electricity does not mean tiny little sparks, it means big, knock you on your butt sparks. One story involved their dog deciding that the new christmas tree was “indoor plumbing”. Well, I’m sure you get the idea. :slight_smile:

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I’m not mistaken. I know what I’m talking about. I just don’t seem to be getting the facts across clearly enough.

Please forgive me. I don’t have time to dig up the documentation to support what I’m trying to tell you, but it’s out there.

This information is in any book that discusses wood technology. It’s basic material, and it’s important for woodworkers to understand. It affects how wood behaves to such an extent that ignoring the dynamics of the moisture cycle (see my earlier posts in this thread) can cause a piece of woodworking to tear itself to bits right before your eyes when the furnace starts coming on a lot, or when the furnace goes off in the springtime if the piece was assembled in a heated space in the winter.

Anyway, thanks for all your kind help. I really do appreciate it.

Best wishes,
Jerry

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(Those of you not interested in a little pontificating on some applied science can skip this one.)

While I found this initially a little unbelievable, it got me thinking, and it’s a very interesting problem, and I don’t at all doubt you. My initial post was based on simple physics (remember I’m the one who brought you the spherical cow :slight_smile: ). I just figured that the wood would want to equilibrate with the surroundings as though it was an osmosis problem – that is, that the concentration of water in the wood would equal the concentration in the surrounding air.

But it gets much more interesting. I deal with dessicants at work and himidifiers at home. The dessicant is a material that absorbs water from the atmosphere – it’s usually an extremely porous substance on which the water adsorbs, but in some instances can be a hygroscopic substance like silica gel that likes to make a hydrate. In most cases this is a reversible process, and you heat the dessicant to drive the water off. OTOH, I’m not exactly sure what the humidifier is, I suspect a gel, and it will make a constant humidity in a volume that’s small enough for it to humidify. I have a couple that keep a constant 65% or so in a few hundred cubic cm’s. To dry those out, which is occasionally necessary, you put them in the refrigerator.

So there are two distinct classes of materials that you dry out in distinctly different ways. There’s no way in a million years (well, probably a few years anyway) that you’ll rid dessicant of water by putting it in a fridge, but it’s a dry atmosphere in an absolute sense. OTOH, something that’s designed to give off water dries best in that atmosphere.

So I guess it’s still counterintuitive, but I can see how a complex material such as wood would be sensitive to relative rather than absolute humidity.

Thanks for bringing up an interesting subject, Jerry. I learned something new, which everyone should do every day.

17

Jerry, I’ve visited Yvon Le Coant’s facility by St-Brieuc, Channel shore of Brittany.

It’s a huge loft which used to be a major coal and fuel storage. Alone, the main room of the workshop is about 1800 sq. ft

There, he stocks his wood (mostly A. blackwood, kingwood) and works his mills and lathes.

I asked “how about heating in winter?”. He said heating the place would cost too much, and he just wore sweaters… Only his office room is vaguely heated.

Now, this is the shore of Brittany: an extremely mild climate, where it seldom freezes, and a rather damp climate due to rainfalls and marine atmosphere. Even with the heat wave hitting recently Western Europe, northern Brittany escaped the 100-plus temperatures which affected all of France including my Southern Brittany.

I guess Yvon’s main concern may be to protect his tools from rust and saline corrosion…

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Hi, Chas.

Very interesting post.

You see, what I mainly know about is wood. I don’t know much about dessicants and humidifiers.

It is my understanding that wood comes into equilibrium with the relative humidity of the air in which it’s stored.

And the problem with wood is that it expands and contracts in one dimension (across the grain) and remains stable in the other dimension (longways to the grain) when the relative humidity increases or decreases and the moisture content of the wood rises or falls to come into equilibrium with the relative humidity of the air.

Again, the major culprit in this situation is central heating.

When you take winter air, let’s say at 20 deg. F. and 60% relative humidity and bring it indoors and heat it, the relative humidity goes way down because the absolute amount of water in the air hasn’t changed (disregarding cooking, respiration, etc. for simplicity’s sake) but the temperature has increased.

At 72 deg. F., the same air can hold much more moisture than it could at 20 deg., so the relative humidity goes down precipitously when you heat the air without adding more moisture.

Without being sophisticated in understanding dessicants and humidifiers, it seems intuitively accessible enough that air that can hold a lot more moisture would tend to dry things out, while air that’s holding closer to the maximum it can hold will have less tendency to dry things out.

This is why we get dry skin and the doors get loose in the winter when the furnace is on.

Designing things made of wood, this has to be taken into consideration unless you’re building in a place like the Phillippines or Yvon Le Coant’s loft where there are no furnaces.

Thanks again for some thought provoking posts.

Best wishes,
Jerry

P.S. Here’s something I’ve often wondered about that came up in thinking about this thread:

How does a frost free freezer work? It seems to me, every time you open the freezer door, you introduce warmer air that contains enough moisture that, when cooled to freezer temperature, will have been cooled below its dew point. Where does the moisture go, if it can’t condense on the freezer walls and contents?

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Frost free freezers have a heater that melts the frost. The water drains through a tube into a tray under the freezer and evaporates. It uses a lot more energy to run one than for a regular freezer. They do work great for freeze drying. As the frost is removed, more moisture comes out of the food and is subsequently removed. If you leave a piece of meat uncovered, you will wind up with a mummified steak.

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Thanks for the answer.

I thought there was something fishy about the fact that freezers dry things out so much. In a non-frost-free freezer, those same things would get encased in ice.

Best wishes,
Jerry