My take on humidity.

[Dave Sayers]

Well, I've read the articles and seen the videos and then I've gone out and looked at the large tongue and grooved shed that is my workshop, sitting happily in a tree lined garden and exposed to the weather.
I have considered the articles and the videos and studied the currently available humidifiers and de-humidifiers and I am now using the best humidity detection device available. While I was working on the last guitar I noticed that during periods of high humidity a ridge on the top of the joined and unfinished soundboard would rise up. Having trimmed the soundboard a large section of this ridge is nailed to the wall. When it rises up I take anything delicate indoors. If it is lying flat I leave the stuff out. I must confess that I am not a qualified scientist, but was humidity as an instrument builders problem discovered sometime around the sale of the first electric de-humidifiers? I mean, how did Andrea Amati (1505-1577) live without one? And how do you get the buyer of a humidity controlled guitar to maintain that perfect humidity?

[Dave Bagwill]

Welcome to the Forum, Dave!
I have not even humidified my own body with coffee yet this morning...someone will answer you fairly quickly I think.
Again welcome!

[John Link]

Hi Dave (both of you),

Buyers do what they damn well please most of the time, and it is not limited to just humidity. Don Teeter tells the story of a guy who took his Martin with him on a high altitude sky dive, then wanted all the cracks the dive created fixed under the terms of Martin's lifetime warranty.

One solution for back and side cracks is to laminate those parts. This is controversial as many poor sounding cheap guitars were and are made this way. Yet the legendary Selmer-Maccaferri jazz guitars - not cheap these days by any measure - featured laminated back and sides. Dave Bagwill has considerable experience laminating sides and might be willing to offer more insight into that possibility. Cracks in solid sides are harder to fix than cracks in a flat plate, my opinion anyway, formed from fixing both. The one laminated back I have resonates at a much lower pitch than any of the solid backs I have. I have not used it yet, so I can't say how this will translate into the sound of a finished instrument.

But the top is a different matter. There is little support for using laminated wood for this, the most crucial part of the instrument. True, less expensive archtop electrics have laminated tops, but the general view is they gain consistency and resistance to feedback at the expense of volume and perhaps tone. But being amplified, there are ways to offset these developments that are not available to an acoustic instrument.

I will be interested in Dave's response after he hydrates. He works in what I consider to be quite a humid environment. (It grows the juiciest pears in the world, though.)

[ken cierp]

I believe you can find tid bits of documentation that the ancient makers dried the air in their shops with open fires. Also, plates and bracing was placed in direct sun prior to gluing.

I agree that we make too big a deal out of this -- especially if the instrument is going to spend its life in the location where it was built. However, making sure the plates and braces are at their smallest dimensions prior to glue up is very important -- having the shop at a constant low RH, not so much, but a good practice so assembly/construction can take place at anytime.

[TonyinNYC]

Hi there new Dave!
Humidity is definitely an issue that needs to be considered when building. Build at a high RH and then take the finished guitar to a low RH environment and you will likely get cracks somewhere. Probably in the top and back plate. My solution to this is to build when RH is quite low. I live in NY city and the RH gets nice and low in the winter time. So that is when I brace my tops and back and when I glue them onto the rim. The only issue I have had is that the action gets high in the summer and low in the winter, but my guitars don't need to be stored in constant RH environments to avoid cracks. My solution to the action issue is to have two saddles for the guitar. When the owner changes the strings in the spring, they install a lower, "Summer Saddle". When they change the strings in the fall, I have them put the "Winter Saddle" back in. It is easy to do when the strings are off and so far, people are happy to do it to maintain low action all year. I mark the saddle so they know which way to install it. My brother keeps his guitar on a stand all year. It is never in a case. He has had no cracks at all.

[mike-p]

I've been drying my 'Shop' (err, living room) With an open fire. I must be an old master luthier.

[Dave Sayers]

I have top say that I think a constant humidity, even if it is high, is ok. I certainly don't seem to have cracks appearing all over the solid wood I'm using, and the Sapele I'm using at the moment is rather ancient and very brittle as it was part of a job lot from a house clearance, probably from some cabinet maker who is now deceased. I can see there would be problems taking a guitar from my workshop to somewhere extremely dry, or very cold. In all honesty I've seen two guitars that were suffering from humidity troubles; one had been hung over a radiator and the other had been left in a freezing horse trailer for months on end at sub zero temperatures. They both came back to more or less normal with some proper care. In England, where I am, the humidity tends to change gradually through the seasons. I doubt if that stresses the wood so much.
I've included a picture of Sapele build; it's an experiment as it's the first scratch build I've done, and I also wanted to install a piezo pickup and reinforce the side to accept the controls. The wood wasn't quarter sawn, but it still seems to have good tone. It really is extremely brittle, though. I originally thought I would use it to practice side bending on my new machine but the results were so good I carried on.