Official Luthiers Forum!

Hi All....

My shop is outside..and here in North Florida we get a wide range of temps and humidities year round. My shop isn't SEALED...but it doesn't have giant gaping holes in it either. It breathes.

My question is can I get away with just humidity control out there. I have a unit I can use that will accept a hose out to run out of the building.

I will air condition it if I have to....but don't want to. You'd need to see the inside to understand.

Anyway...tried to search for this and found lots of information on what the humidity should be but not answers to 'one without the other' question.

THANKS!!!!!

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There is no difference between the man that thinks he can....and the man that thinks he cannot.

The RH is the most important thing my friend. The temperature is of course so that we are comfortable working in the shop AND needs to be acceptable for glues and finish to set-up and cure too.

I suspect in Florida your issue is that the humidity is to high and you don't need to worry about putting humidity into the air?

Hesh you placed the hammer squarely on the nail. In Florida...we don't worry much about putting humidity INTO the air....too much already...especially during the summer months.

With a controlled RH...can I leave my builds in the shop as they progress?....I would think so. My wife has my house looking like a twinky in a peppermint wrapper...nothing else...not even air...will fit.

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There is no difference between the man that thinks he can....and the man that thinks he cannot.

A twinky eh? I hear that Twinkies were standard fare in bomb shelters in the 60's and 70's because they last forever.......

Yes with controlled, constantly, RH you can leave your work-in-progress laying around but perhaps put some sun glasses on it....

I should have mentioned that a dehumidifier will produce a good deal of heat and raise the temp in your shop. In my 11 X 11.5 shop my dehumidifier raises the temp in my shop 3-4 degrees......... So the AC may be a good idea too. It will be helpful to seal up any drafts as well but no one is saying that you need to become a Hostess cup cake......

You have to keep in mind that the two are interlinked. the ability of the air to retain or evaporate moisture is in a direct relationship to the air temperature. It is hard to exclude one and effectively control the other.

Let me restate that. It is difficult to consitantly control the humidity unless you first consistantly control the temp. you could control the temp and not the humidity.

It is bugging me for a while now...my shop stays within 45 to 50, rarely 55%. But it is cold, 17-20 degrees C (less than 70 F)
In the summer when there will be 30 degrees or more, the actual amount of water in air (absolute humidity) can even double what there is right now.

When ppl recommend 42-47%, whats the temperature range for that?

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Build log

65 to 75 F

Howdy! - The humidity we talk about in this forum is RH - Relative Humidity. It is relative, as Michael says, to the temperature. The absolute humidity is the measure of the mass of water in vapor form in a given volume of air. Relative humidity is a percentage of the total mass of water a given volume of air can hold at a certain temperature. A cubic foot of air at 75*F can hold X lbs of H2O (100% RH). At 50% RH it is X/2 lbs H2O.

Only if you lowered the air temperature to the dew point (the temperature at which water vapor begins to condense) or below would the absolute mass of water vapor in the air begin to lower. At that point the relative humidity would be 100%. If you had a sealed room, with no vents or leaks, the absolute water mass in the room would not change with change in temperature as long as you were at the dew point temp or above.

In that same sealed room, if you were to raise the temperature you would lower the relative humidity but the absolute stays the same.

With a hygroscopic (water absorbing) media such as wood you are interested in maintaining the moisture content in the wood at a certain level to prevent changes in the wood volume (shrink or swell). If you were to allow the relative humidity to rise in the room where you keep your tonewood the wood will seek a new equilibrium in water content. Therefore, it will absorb water from the air causing it to swell.

I live in southeast Texas where the climate is very similar to south Florida. I keep my tonewood and all guitar parts inside an air-conditioned room. My shop will have an air conditioning/dehumidification system when I build it out this summer.

I noticed this last week in the house when a front came through and the outside temp went to the low 40s and the heat kicked on that the RH went down 10% to 50%. I had also seen the RH drop when the outside temp went onto the low 80s a few days later and I kicked on the AC. It had gotten to 60%! way too high.

I begin to wonder why most building is being done in drier climates????????

Ah well, good luck and best wishes,

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Steve Walden
Aspiring Builder,
Bartlesville, OK

I just wrote: "Only if you lowered the air temperature to the dew point (the temperature at which water vapor begins to condense) or below would the absolute mass of water vapor in the air begin to lower."

This is how a dehumidifier works. Moist air is drawn over an evaporator coil (the air conditioning type that is evaporationg the freon refrigerant inside) where the air is cooled below its dew point and the water vapor condenses on the metal coils, drains down into a container or out to a sewer line. The air is then blown back into the room over the condensor coil of the machine and it regains the heat it lost an then some.

If the water in the container is left to evaporate in the room it will raise the absolute and therefore the relative humidity back to where it was before but with the added heat of the refrigerant compressor and fan motor.

Don't ya love water????

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Steve Walden
Aspiring Builder,
Bartlesville, OK

unlike most of you I fight the battle frome the other side of the fence. Our average rh her is in the mid to low 30's most of the year and really varies vary little. During the winter it will get much dryer 10-20% some times. So I fight to keep my rh in the shop around 40-45% I know this is less than most of you but to keep it around 45-55% I would be adding many gallons of water into the shops atmoshere every day.

That is the crux of the matter! It is easier and cheaper to put water in the air than take it out!

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Steve Walden
Aspiring Builder,
Bartlesville, OK

I don't have any trouble maintaining 42-48% RH and the lowest my temp gets is 68F and the highest in the summer is 83F. But 83F is not very comfortable so I work in my boxers and stand back from the drum sander........

Forgive my shouting, please.

Hesh: TMI

I just love these new emoticons!

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Steve Walden
Aspiring Builder,
Bartlesville, OK

I still want one scratching the head

For those of us that watch Fox and Friends on Saturday morning We all know of the New york City Naked Cowboy That plays guitar on the strees of NY city in his BVD's for tips

Well it seems we here at the Luthiers form now have our own Naked Luthier thickness sanding in his Hanes comfort band boxers

mmm I might be missing something but here in new york in the summer it can easily be 85 f with a relative humidity level of 80% florida is worse in the summer! I regulate the relative humidity of the room I work and store my wood in and dont worry so much about the temp, right now though I am not using hide glue .. ... Jody

The atmospheric conditions of any given location is susceptible to the moisture that the winds bring in so you can easily have 100 degree days with 90% humidity in an open environment. IE the environmental conditions will overwhelm the airs ability to evaporate the influx of moisture so you have humidity levels that are sustained at higher levels than if the atmosphere was isolated form the constant influx of moisture.

While the glue you use is a factor it is really the movement of the wood that is the big issue. When the environment changes quickly to dry the wood shrinks and can cause crack and break glue joints. This is really the biggest concern with RH. But when the environment changes to wet you have swelling and this can cause parts to push on each other and cause problems as well. If a guitar is built in a 30% environment and always stays there this is not a problem. It is when It changes environments that causes issues. Most of us build at 45-55% because that is near the average Rh the guitar will likely live in so the affect of the difference in the build environment and the owners environment is minimised. that is really the Cruz of the issue.

Here's a wood movement calculator I've found..

http://justwoodworking.com/software/wood_move.php

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http://www.PeakeGuitars.com

Hesh, you don't ever want to come and hang out in my shed. The locals would be pulling on a jumper at 83F . It's a really nice a cool day here and we've got down to 84F. Going to be raining soon as well so the RH is going to go through the roof.

I've had to just worry about RH. To use the air conditioner as well would blow the budget, with the price of electricity here. Australian's rarely seem to worry about insulation etc. so I've slowly become acclimatized to the tropics. My dry room is regularly over 40C or 104F +, but it's quite comfortable to work in 'cause it's a dry heat

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Allen R. McFarlen
Barron River Guitars & Ukuleles
Facebook
Cairns, Australia

Temperature is very important to me. Warmer air holds moisture better than cold air, and this speeds up the process of balancing moisture in wood to the ambient moisture level. The most dangerous times for me to have new wood that is not yet aclimated is in the summer when it is hot. Hot and low moisture will draw moisture out of wood rapidly and I run a high risk of cracking, splitting and such (especially in large form softwoods, that are still drying). Same wood in winter(cool temps) even at moderately low moisture levels does much less damage, as the air can't pull moisture out as rapidly.

After the wood is fairly dry, and in my shop. My goal is mainly to keep the changes slow and mild (even ambient moisture and even temp, in a range suitable for glueing and finishing), if the moisture levels rise or fall a bit, I just want to make sure the temperature is working to my advantage. I try to keep it simple, avoid very hot and dry conditions or very cold moist conditions (especially if followed by rapidly rising temps).

Temperature and ambient moisture level work hand in hand(relative), in changing moisture levels in wood. Luckily I live in an area that doesn't require much effort to keep this in check. In very hot climates either dry or humid, I would start by creating a well insulated space that could be climate controlled. If you don't have a well insulated space, you will never be able to keep up with what mother nature throughs at you. Then I would try to stabalize the space, to buffer the rapid changes, hopefully allowing the wood to avoid large shifts in moisture levels, and still be able to glue and finish. Trying to create an "ideal" climate when your area does not normally come close to that ideal. Is going to make for tough transitions when your work moves into the real world(locally). If you are shipping your work out of your area you probably would be wise to shoot for a fairly neutral shop climate (that "ideal" climate, which is just a good compramise), to reduce the initial aclimation when it reaches its home.

That is my take for what it is worth.

Rich