Official Luthiers Forum!

In my heated basement the hygrometer said 25% yesterday.The colder it gets here in Tennesse the dryer it gets.I`m thinking about a humidifier.What do you think ,is it too dry?
                               James

_________________
James W Bolan
Nashville Tennessee

I'd say it's too dry. Most builder try and maintain 42-48%. Some will go lower as there can be large swings in the humidity as you see.

The real question is where is the guitar mainly going to live? What will the lowest humidity be and for how long? The guitar will be able to withstand about 10-20% drop from the construction humidity, but after that you will start to get cracks and than you will need to repair.

But you also have to remember the summer months when the humidity usually gets considerably higher.

It's certainly a battle, that's why most have settled somewhere around 45% as most places on this earth of ours will rarely see 100% for any real length of time (inside a building that is, it's been raining here for days )

Anyway, you can set up a small room or closet with a humidifier in it and just keep your wood and guitar parts in there. When you are performing some task on it, pull it out, do what your doing and than put it back. It will usually take a constructed body 24-48 hours to really see any change in humidity (this is based solely on my own observations in my own shop so I could be off here).

_________________
My Facebook Guitar Page

"There's really no wrong way, as long as the results are what's desired." Charles Fox

"We have to constantly remind ourselves what we're doing....No Luthier is putting a man on the moon!" Harry Fleishman

"Generosity is always different in the eye of the person who didn't receive anything, but who wanted some." Waddy Thomson

Got the same problem here in Michigan. RH typically swings seasonally between 20% and 90% depending on indoor heat or the lack of cooling/dehumidification.

I`m not sure I quite understand all the humidity stuff.I`ve owned guitars for years in Tennessee where there are extremes, and never had one crack.Of course I`m not sure what conditions the wood was built in or kept in prior to building.It seems to me that even if it was built in perfect conditions ,it could still expand and contract later due to humidity,or lack of.I`m not really sure that applying finish can completely protect wood.I`ve been in building construction for over 30 years ,And I can`t tell you how many times someone has asked me to plane a sticking door.        James

_________________
James W Bolan
Nashville Tennessee

Oh yeah, expansion and contraction occurs in guitar wood the same as it does with construction wood. The key is the RH when the box was glued together. If you glue the top and back to the sides in 80% RH, it's gonna deform and/or crack when it's introduced to 20% RH for a while. The finish only slows moisture transfer. It can't stop it, even if you coat the inside surfaces. The goal is to build in the middle of humidity extremes so the wood never expands or contracts (the most dangerous) enough to fail. Building if the RH is a bit too low is safer than building when it's a bit too high, unless the instrument will live its entire life in high humidity.

Oh, I should also say that the RH when you glue the bracing to the plates is probably equally important to when you close the box.

Arkansas and Tennessee are very similar climes. I cranked my humidifier about a week ago when the temps fell below freezing. So far I've added 4 gallons and the rh is about 42 currently. It will keep going until it reaches the preset close to 45%.

By the way, what are you doing in that basement?

_________________
http://www.dickeyguitars.com

The basement is where I store guitar parts which used to be my sons bedroom.Its right next to my shop,which is unconditioned.I do think that building when it`s drier is probably better than when it`s humid.But what do I know.I think I`ll get a humidifier.
                        James

_________________
James W Bolan
Nashville Tennessee

A decent hygrometer is a must as well and Tracy recommended one to me that is "right-on" and I know this since I calibrated it.

Hesh, what model is that, and where can one get one?

Thanks!

James,
I have simmilar basement shop condisions.
It can be a pain to try keeping the whole basement at 45% RH 24-7. I built a cabinet for storage that can close durring extreems. Unless I plan to build for several days, I leave the shop as is. I can fire up the humidity for the short term if need be.

Wade

_________________
Wade
Nashua, NH
http://www.wadefx.com

Hi guys.

I'm no expert and i haven't built alot of guitars, but i visited a local luthier once and saw him glueing up a guitar on one of those red hot sweltering, muggy aussie summer days.
The kind you have when you feel like all the house fixtures are going to melt off the walls.
The humidity would have to have been up around the 100 mark.
And he wasn't using a humidity controlled room.

I was surprised and i wouldn't have done it, but he's been at it 30 years and who am i to question his methods

He glued it using tite bond, which is more elastic than HHG and probably just that little bit more forgiving in terms of its ability to cope with humidity extremes.
The other thing is that some timber billets are extraordinarly stable with humidity, and another billet of the same species can react very poorly to the same conditions.
I'm sure all of this counts.

Perhaps this might go some way toward explaining why some guitars crack easily and others are close to bomb proof.

I don't have a barrometer and i just glue up if it feels right.
Which is probably strictly wrong but so far its worked.
I probably err slightly on the side of dry.


cheers,
Claire









Claire39101.6210648148

Clare...dare I say at also my newbie stage, I don't measure the humidity point by point, but get a "feel" for when things get a little humid, or dry...

and the things you have said are CERTAINLY things I have been thinking about lately, especially with regards to the pre-technological age of guitar building.

I imagine that if a guitar was to be shipped across into a zone in the world where the humidity is opposite to where the guitar was built, then yes, strict humidity levels have to be observed. I don't know..

Just my 2 cents. Forgive me if I'm wrong about this. Sam Price39101.6215856482

I think what you said Sam makes a lot of sense.The humidity in my shop is about 15 degrees higher than in my basement, but quite a bit colder.I`m concerned with this whole situation because I`m going to build my nephew a guitar here in Tennessee that`s gonig to be living in Seattle.        &nbs p;  James

_________________
James W Bolan
Nashville Tennessee

I think that one thing that might make for a more relevant discussion and actually help to bound the RH range is to ask the question in a slightly different way. That being, what kind of tolerance is acceptable in the moisture content of the wood? For example a range of 35%-45% RH will bring spruce to a equilibrium moisture content (EMC) range of 6%-8% (corresponding to the RH). Is a 2% change in EMC acceptable? Do we really need to controll our ares within 1-2% RH, probably not. They do need to be controlled in my opinion, but to ehat level I'm not sure. I personally shot for 40%

_________________
Jim Watts
http://jameswattsguitars.com

I am also a newbie.  Actually, I am setting up my shop from scratch.  I will be working out of an insulated garage.  I live in Phoenix, so I also have to worry about being too dry.

The humidity inside my garage and inside my home is almost exactly the same (since I have an insulated garage).  It ranges between 15% and 30% based on the time of year.  I'm afraid that if I bump the humidity in my shop up to 40% or so for wood storage and building, then store the finished product in any home in Phoenix (which would be low humidity just like mine), the instrument will be prone to cracking because of the large swing between build humidity and storage humidity.

Should I just leave the shop humidity alone since it's so close to inside humidity?

Thanks.

I have about 6 digital hygrometers from various different companies and they all range at about 5% of each other (even though they say accurate to +/- 1%). I work in occupational safety and took one of our calibratable instruments home ($5-600 unit) and it measured quite different than the digital units. Then recently, following a thread on MIMF I used my digital thermometer to get a wet bulb/dry bulb reading and used those readings on a psychrometric chart. The result? The two digital hygrometers in the shop were showing 35% and 34%, the wet bulb/ dry bulb reading was 50%. Although 15% may not be much of a difference the concern is this. At 35% I would be humidifying the work area and by the time I got the humidity up on the digital hygrometers I would be in a very poor guitar building environment. I just did this the other day and will do it again before I decide about what I am planning to do but I leave you with this as a warning about the accuracy of digital hygrometers and not to trust their claims of accuracy. By comparision, I have another analog hygrometer that I got from Lee Valley for like $10 that actually agrees with the wet bulb dry bulb. I thought it was a cheap peice of cr@p. Guess not! And it comes with instructions on how you CAN recalibrate it.

ShaneShane Neifer39108.7869560185

_________________
Canada

Hi Desert Cajun, welcome to the OLF!

I really like your username, i'm a Cajun kind of Canuck myself!

Have fun building!

Serge

I think RH really needs to be considered and controlled for any guitar that will "live" in a different environment. If it's going to stay in an average 80% RH, it could be built at that RH. Since I'm not sure where mine will end up 20 years down the road, I'm trying to do the critical stuff with humidity in the 40's.

Ron

_________________
OLD MAN formerly (and formally) known as:

Ron Wisdom

Somewhere in the middle of Arkansas......

Mario had a system for calibrating hygrometers that he posted somewhere (may have been here, maybe Flatpick-list). I've got two digitals and I assume the truth is somewhere in the middle.

Andrew

Andrew,

I have six! I think that tey are all wrong and are reading way too low! The one analog one I have is always much higher and now that I have used expensive humidity instruments and have done a wet bulb, dry bulb test, as per a current thread under the tools section of MIMF, I think that my digitals are around 35% when it is actually about 50%. At 35% I would start to hydrate the shop while at 50% I would start to think about dehumidification (I have capacity to do both). So you can see that this is a real problem if these inexpensive digital instruments are in fact huge on error! They should be tested with another method, and since most of us have thermometers, a wet bulb/dry bulb method and a chart you can get off the internet is probably the best way to do this.

Shane

_________________
Canada

Put the hygrometer into a large zip top plastic bag, also put in a small open container, 20ml medicine dispenser or such, that is about half full of damp salt, just damp enough so that there is no free water. Zip up the bag so that it is air tight, but with some air in it. Let the whole thing sit for 48hrs or so, the hygrometer should read 75%, any difference is the error in your hygrometer. My digitals average 3 or 4% error and I put a label on each to tell me.

Colin

_________________
I don't believe in anything, I simply make use of a set of reasonable working hypotheses.