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Seems like a lot of new builders are having problems with humidity,myself included...The back of one of my guitars flattened out and I blamed it on everything except relative humidity.....I have done a lot of reading on this subject and indeed I have a humidity problem....The way I looked at it was ....I have some cheap guitars here and there are no problems with them....I find out that a lot of these instruments are made from plywood veneers which handle humidity a lot better than the solid woods...They just don't measure up in the sound department.....I know I have to keep my relative humidity up to at least 40%....I know I have to get a new source of heat other than the forced fan electric heater......A couple of questions.....When you sell a guitar do you make the customer aware of the importance of proper humidity care.....What is a good humidity control system to buy?.....Thanks,Larry

Larry-
I'd start with a humidity meter or measuring system - I have a Caliber III hygrometer (ebay $20) and it seems OK. Others prefer a 'wet sock' thermometer (psychrometer) which no doubt you have read about.
You are correct that in most parts of Canada you will need to humidify in the winter and possibly/probably dehumidify in the summer.
Your source of heat doesn't affect the relative humidity level, so don't worry about changing that- you need to get a humidifier to pump some moisture into the air if your RH is low. You will definitely have a challenge if you want to try to just warm up your shop when you are working in it- I don't think you will be able to control the RH (and your wood needs to live in a controlled RH environment) unless you keep the shop at a reasonably even temperature as well.

Here on the west coast, it's pretty damp all winter so the dehumidifier is kept pretty busy- fortunately they also pump out some heat so it's not all 'wasted energy'.

Cheers
John

the humidity outside your house or shop has a lot to do with it. If you live in freezing temps, you will have to pump a lot of water into the air.

if you can't do a whole house or shop, then you need to do a single room with a smaller humidifier.

Arkansas is fairly mild but we've had a few nights of freezing weather and the humidifier in my shop has been running. I've put in six gallons or so the last couple weeks. And that is a 16 by 24 one room shop. A house might require a couple full size humidifiers to do the job. Your skin will thank you too.

Taylor's Tech sheets are great info.

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http://www.dickeyguitars.com

Thanks guys....Points well taken...I  am using a shed at the moment for building...I keep it heating as best I can....The temps here can be very extreme...I have seen the temp change here in a 24 hour period as much as 40 deg....So as you can see it is going to be hard to keep a constant temp there..I plan on building a proper workshop in the spring and have a room that will have some form of humidity control........I read all the post in here just about every day and get a lot of good info from the experts...Some post do confuse me....Like baking woods in the oven,,storing them in attics and dry places but when you glue them up you the air has to be 45-55 RH.....
What is the best procedure for me
Do I prepare all the components of a guitar and wait for a proper RH day or condition to glue them up?
When you glue similar woods together (spruce bracing to spruce tops, Mahogany kerfing to mahogany sides,,,etc) is RH a factor?
When you bring a piece of wood into a controlled RH room , how long does it take the wood to adjust to the RH? Thanks for taking the time to read and answer some of these questions....Larry

Your best bet at this point is to stop, and wait 'til spring when you have a proper space to work in. Sorry, but 'tis the truth.

Larry what Grump said.

The big difference between building guitars and a completed guitar when dealing with RH and temperature shifts is that the design and construction of a completed guitar permits it to be more tolerant of less than ideal conditions.

When we build guitars it is not unlike having half a span of an uncompleted bridge hanging out over the river.  When the structure is completed it is much stronger and acts as a whole and not just the individual parts.

A braced top or back that is not quickly attached to a prepared rim AND if the RH swings out of the recommended range will potato chip on you.......

Any cross grain gluing, bracing tops, backs etc needs to be done with stable RH and the work in progress needs to be stored in a stable RH environment.

So really unless you are going to set up a stable RH shop or place to work and store you are taking a long walk on a short pier my friend.  There is no way around it and we are just trying to help you avoid having something very sad happen to one of your guitars.

Last summer I took a completed top that was built in the acceptable, controlled RH range and decided to sit on my back deck and final sand it/clean it up.  I placed a calibrated hygrometer on the deck and it read 56%, not a great difference from my 45% shop I thought.  With in 25 minutes I noticed that the top was flattening out.....  I quickly retreated to the shop and weighted the top in the 25' radius dish that it was built in.  It recovered but again it was not exposed to the change in RH for very long.......

Listen to Mario on this one... I sold an early guitar to a friend for CHEAP. He wanted one he could afford, & even though the back had collapsed some, he loved the guitar.
Next thing I know, he's moving from the moist west coast to northern BC. I did warn him that the guitar was built before I built the humidity controlled assembly room in my shop, & would not take well to the new environment, but I guess he didn't believe me.
Long story short, that guitar is on my bench right now... The cracked top has been removed & I have just finished planing the back braces off.
I baked a new top yesterday & all the parts will sit in my humidity controlled room for a couple of weeks before I go any further.
It just isn't worth taking the chance, building in uncontrolled (or at least, unmonitored) conditions. That guitar probably would have been fine if it had stayed on the west coast. The dry & frigid north was just to much for the poor thing!
I now give my customers a short handbook on the care & feeding of their new instrument. Humidity issues are covered in some depth. I get them to sign a page for my records stating they have read & understood the instructions.

You can do a bit of processing without much danger. Keeping woods in a controlled area will work and just bring 'em out to work on it. But RH is king and we must serve the king or suffer....

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http://www.dickeyguitars.com

I sometimes wonder about the fact that RH is, by definition I believe, a measure of how much moisture is in the air at a given temperature relative to how much moisture it can hold at that temperature.
Would a RH of 50% at 50F and a RH of 50% at 90F cause wood to take on or release moisture at the same rate? Would the wood (sorry about that) reach equilibrium at the same moisture content?   I'm already in over my head so any comments are appreciated.

Yes.

"relative" humidity means just that, relating to the temperature.

a perfect example, in our home right now, down in the main part, where it's 70°f, the RH is at 33%. Up in my den/office, where it's 63°f, the RH is 41%. Same air, same building.

when we warm the air, that air expands. The moisture content remained the same, and what we have is less moisture for the amount of air, thus, lower RH. Still can't picture it? Blow up a balloon; put the ballon outside(or in the frudge) where it's cold. What it shrink. That air shrank, but the moisture that that air contained, didn't, so the RH went up inside the balloon. Our shops/homes are just like the balloon, evn though they have some air exchange with the outdoors.

Hygroscopic materials(wood...) don't care what the temperature is; they constantly seek to balance themselves to the moisture level of that air. So, if you placed a wood item in that balloon, the wood would try to pull more moisture into itself as the air cooled, and if we warmed the balloon, it would give off some moisture to the surrounding air.

I have to say, that is a really, good explanation, Grumpy.   Were you ever a science teacher?

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

[QUOTE=WaddyT]I have to say, that is a really, good explanation, Grumpy.   Were you ever a science teacher?
[/QUOTE]

I was thinking the same thing!  I am a science teacher, and that was very well done, Grumpy.  I was learning.

Thanks for that Grumpy!  That was the best explanation of the subject for my feeble mind.  I was also wondering if you were a teacher.

That's Professor Grumpy to you people!   

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Eagles may soar, but weasels don't get sucked into jet engines.

Can you image ME with a class of teenagers? At the end of a 45 minute class, it'd be me, the teacher's pet, and the quiet recluse who never speaks, left. Everyone else would have bee sent to detention or the hospital....

I'm not teacher material, trust me.

Maybe from a safe distance.  

OK,OK, I'll go to detention.  

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Some of the best teachers I ever had in school or college were the ones that could put complicated theories or ideas into laymens terms so that anyone could understand the concept.

I think you did a greaqt job of explaining this!  Well done!

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Reguards,

Ken H

Thanks guys for all the info....Thanks Mario for putting things in perspective...I have been doing a lot of  reading on RH and I just finished reading a archived thread by RobertD....The info and pics do a fine job on getting the point across about having the proper RH levels....I will not do any more building until I have the proper control on humidity....I will have to complete the three that are near to completion and hope for the best......Not the way to go but a lot of valuable lessons learned.....Thanks Larry.....

Filippo buddy I have a little Gold Star (Borg bought) 30 pint dehumidifier that works fine.  In the hot, rainy summer I have never had to turn it beyond 1/2 way up for my 11.5 X 11 shop.

But they are noisy and rattle as well being PLO's (plastic like objects).

The thing to consider as well is that they generate heat as they evaporate moisture and can raise my shop temp 3-4 degrees........  They also, when running since they are compressors, can tax your circuits when you flip on a few power tools and dust collection.

But it is not an unbearable level of noise or heat and mine only runs perhaps 1/4 of the time to do the job.  You are thankful however when it shuts off.

And unless you can plumb it to a drain be ready to schlep water to empty the dang things.  All summer long I am emptying the dehumidifier and all winter long I am refilling the humidifier - man this guitar building is tough.......

BTW regarding humidifiers I have a whole house console unit in my living room that does the heavy lifting.  In the shop is a smaller version of the same digital humidifier from Sears.  The shop one rarely runs and is whisper quiet but ready to back up the whole house unit, at least for the shop, should the larger one fail.

My living room stays pretty constant around 45% RH and so too does the shop with the assist of a dedicated, local unit.

For humidifiers I have found that it pays to go the over kill route and turn them way down to a quiet level.  For dehumidifiers I believe the opposite is true, buy one just big enough to do the job and you won't have to deal with a higher level of noise and power consumption.

I bought my dehumidifier at Home Despot (pun intended) - I think, a Delonghi, I'll check tonight, it was the mid range one.  only has two speeds, high & low, but both are reasonably quiet, and it does have a good digital humidistat on it. It works well.  I used the water this summer to water shrubs and a small tree I planted in the spring.  It does play havoc with the temperature in the shop though.  With the 90% humidity and 90 - 100* temps around here, I was dumping about 4 - 6 gallons of water a day.  I had to empty it 3 times a day some days.  I can put a hose on it, but then I can't put the water where I want it to go.  I'll eventually get lazy on that, and install a hose, and run it to the French Drain in the crawl space under my house.

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Hi everyone, not to confuse things further, but what is the relationship between RH and moisture content of the wood. When wood is allowed to season or stabalize in an RH controlled environment, what is happening. I am new to this (in fact this is my first post here) and I was just curious for example, if I order some wood, bring it into my shop, how long do I need to leave it alone before starting a project with it. What kind of moisture content are you looking for in the wood, and how is it measured. Thanks

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Kurt Thomas

"There's a first time for everything even if you do it by mistake."

Kurt, never hesitate to start a new topic.

Welcome to the OLF.

Most wood vendors recommend 3 to 4 weeks Minimum.

But it is possible it needs additional seasoning.

Many luthiers want to own their wood at least a year before starting in on it. That way they know it's acclimated.

Meters are a luxury, a lot of us do not have.

Meters are how you know.

That or, you seasoned the wood yourself and know.

I bet someone already beat me posting..... grin....

Good luck building, welcome to the OLF.

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http://www.dickeyguitars.com

Don't necessarily go the Sears dehumidifier route. I've gone through one that worked fairly well...but I've taken two back that ran ALL the time, although they're supposed to have a digital sensor that kicks the unit on when the humidity gets below a specified amount. Doesn't work.

Avoid the Sears brand, which is probably made by someone else.

Bill

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Eagles may soar, but weasels don't get sucked into jet engines.