Increasing Humidity

Now that heating season has started our shop is running from the high teens to the low twenties in R.H. I'm wondering if blowing a fan across a 55 gallon drum full of water can raise the humidity into the 50% range.
The shop is about 50,000 sq ft and maybe 1 mil cu ft and the temp ranges from 60 to 70 F.
tom watson
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Can't help you there, but it looks like ComCaustic is violating their own policy?
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Yup. That hoss gets ridden till she founders.
tom watson

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"Swingman" wrote

And I learned another word today!
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4ax.com:

You've got 2 of 3 parts to a traditional humidifier. There's also a filter media that's primary purpose is to act as a wick and spread the moisture out before the fan blows it in the room.
The drum and fan will have some effect, but you might need a towel or something to use as a wick.
Puckdropper
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On Sun, 26 Oct 2008 10:18:14 -0400, t wrote:

Tom:
Think of it this way, as the air steam from the fan is somewhat like a cylinder, and the water pan slices a part of the air stream across the surface of the water. Only that small part of the air stream in contact with the water pan will assist in water vaporization. Yes, it can be done but at what efficiency cost.
Room humidifiers use some sort of water wick that alternates between being dunked (immersion) in the water and being presented to the fan as a much larger damp surface area for the air stream to effectively assist in water vaporization. Much more efficient.
Actually, Sears sells several room humidifiers (difference is mostly in the gallons the tank holds and the size of the replaceable wick) that actually work quite well. My Sears room humidifier has lasted almost 20 years with normal maintenance of the occasional V belt, wick replacement annually and a drop of oil in the motor.
There is no reason you could not improve on the Sears design and make you own version. I suspect the 1st design improvement will be to come up with a filter on the fan's input air to cut down on the saw dust that will clog the water wick.
Don't forget the bacteria bit on room humidifiers. Room humidifiers are famous for growing nasty bacteria that ends up as congested lungs on your part. Tablespoon of household bleach each week helps out. Just make sure no shop pet gets a mind to drink.
Just ignore the Neanderthal woodworkers who claim a dry woodworking shop is justification for bending wood. Bending wood requires a steam box, boiling water, and a heat source to boil the water. Way too much extra work just to add some humidity.
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Climb into the drum every 30 minutes or so, you'll be very comfortable.
B.

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Keep in mind that if your shop is that cold, you humidify the shop, and later warm the shop the humidity will condense on the cold iron stuff. You might create a rust problem.
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Now, *there's* a drive by if I've ever read one.
jc
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"t" wrote:

Right idea, wrong scale.
You're going to need something close to 1% of the total area for your water pond.
BTW heating the water will improve the evaporative process.
Lew
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Presumably, that's not half air/half water, but rather 50% relative humidity that you're talking about. Why that target? Is your shop really always fully heated? Mine isn't.
Wouldn't it be better to humidify to a point where fully-dried wood has neither uptake nor loss of moisture? The interesting quantity is EMC (Eqilibrium Moisture Content).
The USDA wood handbook has a formula, equation 3-3, for this:
M = 1800/W *(K *H/( 1 - K*H) + (...other terms) )
where M is the percent moisture content (something around 7% is common for fully-dry furniture), and W is a temperature function
W :== 330 + 0.452 *T + 0.004157 *T**2
K :== 0.791 + 0.000463 * T + 0.000 000 8447 *T**2
H :== relative humidity (50% would mean H = 0.50)
where T is Fahrenheit temperature.
In other words, one cannot keep wood stable at varying temperature with constant relative humidity. When one changes, the other does too, OR the wood starts to shrink/swell/cup/warp.
USDA wood handbook, FPL-GTR-113, is available online, is about 14 MBytes in size. <http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/fplgtr113.pdf
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whit3rd wrote:

I was curious so I plugged the above into a spreadsheet to check it out. It turns out the effect of temperature isn't all that large.
For relative humidity of 30% the EMC varies by 0.2 when you change the temperature from 32F to 107F.
At RH of 50% the effect is larger, but it still varies by less than 0.4 over that temperature range.
Chris
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Chris Friesen wrote: ...

...
Yes, if it weren't, wood wouldn't be much of a useful material, after all... :)
The RH in an inhabited space may as well simply be controlled for comfort and economical heating/cooling considerations and for a shop somewhat the same w/ the primary emphasis on avoiding condensation in unheated areas for rust prevention.
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Thanks for the responses to this point. My thought was that the transfer of moisture from the drum to the air would be osmotic and would be enhanced by the fan.
tom
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