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chuck in ny
02-03-2016, 05:20 PM
what humidity levels should be maintained? my shop goes from about 20% in the winter, it's the basement of a wood heated house and thus dry, stays in the 30% to 40% range in spring and fall, and is 70% and higher in the summer.
i haven't tried dehumidification. it's 900 sq. ft. with an 8' ceiling. without controlling humidity i would have about 4 months of opportunity to build.
doing normal wood working the summer wetness hasn't caused any problems. this is for trade work done in the local area and is different from shipping instruments to the desert and such.

BlackBearUkes
02-03-2016, 08:07 PM
The ideal for humidity levels in your shop should be 42-50 at all times. The wood should be at 6% moisture content.


what humidity levels should be maintained? my shop goes from about 20% in the winter, it's the basement of a wood heated house and thus dry, stays in the 30% to 40% range in spring and fall, and is 70% and higher in the summer.
i haven't tried dehumidification. it's 900 sq. ft. with an 8' ceiling. without controlling humidity i would have about 4 months of opportunity to build.
doing normal wood working the summer wetness hasn't caused any problems. this is for trade work done in the local area and is different from shipping instruments to the desert and such.

Pete Howlett
02-03-2016, 08:40 PM
Most people dessicate their homes. That rule of thumb Dwayne is just a good idea, nothing else...

anthonyg
02-04-2016, 01:08 AM
There may be a market for instruments built in/for low humidity conditions.

Far too many people buy ukuleles built in jungle humidity and then completely destroy them in a matter of weeks because they live in deserts.

Anthony

Michael N.
02-04-2016, 02:56 AM
what humidity levels should be maintained? my shop goes from about 20% in the winter, it's the basement of a wood heated house and thus dry, stays in the 30% to 40% range in spring and fall, and is 70% and higher in the summer.
i haven't tried dehumidification. it's 900 sq. ft. with an 8' ceiling. without controlling humidity i would have about 4 months of opportunity to build.
doing normal wood working the summer wetness hasn't caused any problems. this is for trade work done in the local area and is different from shipping instruments to the desert and such.

I'd say for your environment it should be nearer 40% rather than 50%. You seem to hit lower humidity than I've experienced in the UK. It's rare that I see RH in the 20's. Even low 30's is fairly rare. It seems to hover between 40 and 50% here, although it can climb (and does) to 70% + in the summer months. Of course that's just my indoor workshop humidity, what I personally have been monitoring over a couple of decades or so.
Given that instruments are much more at risk of damage from low humidity I'd be tempted to build in the very low 40's. You can build a cupboard dehumidifier (or humidifier) that will allow you to condition wood prior to gluing. You can build all throughout the year then.

chuck in ny
02-04-2016, 10:32 AM
I'd say for your environment it should be nearer 40% rather than 50%. You seem to hit lower humidity than I've experienced in the UK. It's rare that I see RH in the 20's. Even low 30's is fairly rare. It seems to hover between 40 and 50% here, although it can climb (and does) to 70% + in the summer months. Of course that's just my indoor workshop humidity, what I personally have been monitoring over a couple of decades or so.
Given that instruments are much more at risk of damage from low humidity I'd be tempted to build in the very low 40's. You can build a cupboard dehumidifier (or humidifier) that will allow you to condition wood prior to gluing. You can build all throughout the year then.

michael

thank you i wouldn't have thought of a cupboard humidifier/de/ in a million years.
here is the deal with humidity in my shop. i have several blowers one of which is always on, one small one larger, that suck air from the wood heated upstairs down through the basement shop. a wood stove produces ultra low humidity. winter humidity readings stay in the 20s, and half the time go below 20% when the meter only reads 'LO'.

edit. i really like your lacote guitar, it has it going on in spades.

Michael N.
02-05-2016, 01:53 AM
You can use a light bulb (one that puts out heat) or buy a very small dehumidifier intended for wardrobes/cupboards. The dehumidifier is probably the safer option and the wardrobe type aren't a huge amount of money. Just place the wood in that environment for around 6 hours, take it out and do your gluing. You can either leave it out or put it back into the cupboard.

Jardin
02-10-2016, 04:53 AM
Greetings
I guess this will be my introduction to the forum. I have been looking around and gathering a whole host of great information from you all but I tend to be quiet in person and online. I have been making instruments of various sorts for most of my life out of necessity (being a poorboy musician). Have always loved woodworking of various bents and now am moving into building Ukulele as well as other Guitar family instruments.

This question of shop conditions really intrigues me and I have of course heard it from both schools of thought were one is supposed to take this seriously and others who look at it more as a mere detail that is optional.

I live in the desert and therefore, with the exception of monsoon season we have low relative humidity. My shop is covered yet open so obviously it is hard to control the relative humidity. I was considering making a conditioning cupboard as Micheal mentioned (thanks for the idea) but my mind has questions as to why. So I thought I would ask what the general experience was of those who have built in conditions where the relative humidity was outside of the ideal range of 40 - 50%.

As I understand it (correct me if I am wrong please) the main concerns are during the glue up and assembly of the body (top, back, sides, kerfing, bracing etc.). I would love to here what peoples experience is or even the theory of what to abide by and why.

I appreciate all the knowledge you all share.

mzuch
02-10-2016, 07:06 AM
I live in the desert and therefore, with the exception of monsoon season we have low relative humidity.

Welcome to the Lounge, Jardin. If you are building instruments for others who live in places with higher or lower humidity, then a building environment of 40% to 50% RH is a good idea. Maintaining a steady RH is also important if your shop environment varies widely, as I've seen braced plates lose their arches overnight when the humidity changes. But if you're building for yourself and your humidity levels stay consistent while you are building, I wouldn't worry about humidifying your shop.

RPA_Ukuleles
02-10-2016, 07:41 AM
Changes in humidity causes wood to grow or shrink. That's the facts, Jack. Mostly across the grain and less so with the grain, as a general rule. Perfectly quarter sawn is about the best cut choice as it usually has the least change across grain when compared to rift cut or slab cut. So there's nothing magical about humidity and why you build in a properly humidified space, only practical issues. Ideally the conditions in which you build an ukulele would be for the conditions it will spend its life in. But now what's the likelihood of that? Yeah, pretty much zero.

So conventional wisdom says build the instrument in the, lets say "human ideal" range of around 50% RH. Many builders would argue a few percent up or down but it likely doesn't matter at that point. The thing is your best chances of uke survivability for any length of time is with wood that is properly "seasoned" which is another way of saying the wood has reached a stable moisture content within, AND that you acclimate it to your building environment for a time before you build with it, AND that you build in that "ideal" RH environment, SO the final uke has the best chance at surviving changing environments it will most assuredly encounter in its lifetime.

Wood does not have to be "humidified" per-se, wood has to be stable before building and then built in an ideal environment, then kept as stable and as close to that ideal as possible. That's the baseline for making a long lasting, happy ukulele.

The build environment should be maintained as close to the shop "ideal" of around 50%. If you build a uke in a dry environment of say 20%, that's just as bad as building in 80% RH. If you build in an environment thats too dry, what will happen to the finished uke come summertime in Florida when the humidity in the house hits 70%? Well, the wood is gonna absorb that moisture and swell in size across the grain. Hmm, whats the big deal with that? Warping, twisting, bulging, bellying, seam separation, etc., and who knows what. Conversely if you build in a high humidity environment, like say the open air shops of east Asia, then someone buys that uke and it now lives in wood stove heated Montana home where the relative humidity in the house is 10%, what will happen to that uke? Warping, twisting, shrinking, seam separation, cracking, bridge separation, on and on. Heck the thing could dry up and implode for all we know.

So now what? Well the best we can do is season our wood carefully, build in a good stable environment held as close to 50% RH and hope that extreme swings of humidity from that 50% (ish) mark will be less extreme than severe swings from building at 20% and then experience 80%. That's a 60% overall change, whereas building at 50% and swinging up to 80% on a summer day is only a 30% total difference. And vice versa for low RH swings.

So really the whole build, every part benefits from being constructed in that stable environment. One can't say the top and linings need to be assembled at good humidity but the bridge attachment doesn't matter so much. All wood should be at the proper moisture content, and assembly should be in the proper moisture environment, and finishing also should be done in the proper environment.

So more than "schools of thought", you have the practical matter that wood reacts to the environment so make sure it's stable when you build with it. Build in the so-called ideal close to 50% environment, to give the uke the best fighting chance to survive extremes in either direction. Then be informed and inform your customers that large changes in humidity in either direction are the enemy. More often than not, dryness is going to be the biggest problem, but that all depends on where you live. So wood, or wooden instruments don't need to be simply "humidified", because that means nothing, instruments need to be kept as close to the ideal humidity - for that instrument. So, if it was built in an ideal environment that most of us have agreed upon, then it should be kept, stored, and used in an environment as close to that ideal as possible.

If every builder chose a different ideal environment, then owners would be chasing some random humidity level based on that builder. If there's a general consensus that we all build in, it makes it easier for an owner to know what lengths they will have to go to to keep their instrument in the proper conditions.

Diogenes Blue
02-10-2016, 09:50 AM
^^^ What Rodney said...

chuck in ny
02-10-2016, 10:07 AM
dr. gene wengert is professor emeritus in wood processing, department of forestry, at university of wisconsin/madison. he is the resident technical adviser at woodweb.com. cabinetmakers and architectural woodworkers frequent the forum.
i asked dr. gene a number of years ago what are the best conditions for laminating solid wood for gun stocks and he recommended a range of 30% or 35%. i would not have the temerity to laminate solid wood in the summer and ship product around the country and see what happens, although it's possible that it would work out. i have too strong an innate feeling not to do it.
i strongly suspect that instruments could be built at lower humidity than discussed here. we could go with dr. gene's 30% and desist building at 50%. pono has a climate controlled operation and someone could find out what they do as their product is perfectly reputable. the low humidity is spooky and the high not much better. it is easier for me to deal with the high and i ordered a gun safe dehumidifier and an extra temp/humidity meter so it's one cabinet away from a setup and being able to build 9 months out of the year.
also worth pointing out is appalachian hardwood is being used and not exotics. the oaks and ashes and birch and beeches of the world are more compliant than tropical wood. rosewood and ebony must be their own challenge.
any thoughts on this don't be shy.

BlackBearUkes
02-10-2016, 04:07 PM
For the most part I would agree with RPA Ukes, but I would go for the humidity levels to be more in the 45% range, not 50. It makes a difference. I also live in a desert area where the levels can drop to 20% in the hard winter months and 55-60% in the summer. My shop is always, and I mean always in the 42-48% range and I have never had a problem with a uke coming apart or being sent back for too dry or wet woods. If you want to make a living at this, don't just try to get by.

Diogenes Blue
02-11-2016, 01:46 AM
I shoot for 45%.

Jardin
02-11-2016, 08:30 AM
Hey thanks for the clarification folks.

All about what I thought. Looks like I will have to move to the indoor portion of my shop for these endeavors (prime real estate).

Makes me curious what the old builders (pre-20th century tech) did to deal with these issues.

chuck in ny
02-11-2016, 11:39 AM
i have it on good authority stradivari kept his dehumidifier plugged in all summer. it's hard to imagine an italian craftsman or worker doing anything but working all they could whether the conditions were humid or dry.
good observation there.

Sven
02-11-2016, 06:27 PM
No doubt they were working hard. I knew an Italian who could dehumidify a bottle of wine in a few moments.

Moore Bettah Ukuleles
02-11-2016, 07:32 PM
Hey thanks for the clarification folks.

All about what I thought. Looks like I will have to move to the indoor portion of my shop for these endeavors (prime real estate).

Makes me curious what the old builders (pre-20th century tech) did to deal with these issues.

Back on the day an instrument was more likely to live it's life pretty close to where it was built. Modern transportation changed all of that.

Michael N.
02-12-2016, 01:09 AM
We don't know what the old builders did in respect of humidity. I can't remember coming across any literature that tells us. In fact there is very little literature of any kind that tells us of their working methods, let alone any humidity control. Of course the Violin family of instruments have something of an inbuilt safety device, the plates are usually deliberately put on with weak glue. Any serious wood movement is likely to pop the plate joint rather than crack the wood. At least that's the theory. Of course there are plenty of old violins with plenty of plate cracks.
At least these days we can measure and control humidity to a pretty fine degree. What humidity you build in depends on a number of factors. The 45% - 50% range is just an average, something that players can try to maintain irrespective of where they live. It's hardly a perfect solution. A couple of years ago I built an instrument destined for SW Colorado. There's simply no way that I was going to build it for the 45% - 50% range. SW Colorado isn't called guitar graveyard for no good reason. So my advice is to mostly build with 45% RH in mind but there are certainly exceptions. Also be mindful that once an instrument has left your hands it's beyond your control. It may end up in the humid rainforest or dry desert conditions.

chuck in ny
02-12-2016, 06:26 AM
you guys must know this. how did the martin guitars from the mid 19th century fare, built i guess in PA, and if people then were anything like they are now, they must have been shipped around quite a bit. there is a lot of information about this traditional outfit.
even without being shipped around they had to live in wood and coal heated houses that were deadly dry.
maybe back in the day people didn't freak out when an instrument developed a crack in time. the consumer has a higher expectation today. these things happen for one reason or the other. some brass instruments get red rot, some don't. you buy it, use it, develop, see how it goes.

DennisK
02-15-2016, 08:43 AM
Some more factors:

Different woods have different expansion rates and brittleness. The higher the expansion rate, the more stress is generated from a given RH% change. The more brittle, the less drying stress it takes to crack the wood. wood-database.com has numbers for many species.

Redwood and western redcedar have extremely low expansion rates, but are brittle. So brace them dry to give low humidity tolerance, because they're not going to generate much stress in high humidity either way. Walnut, on the other hand, has fairly high expansion, but is tough so it can take a big drop in humidity. Brace it in more medium humidity so it doesn't swell up too much during those Florida summers :) Ebony has extremely high expansion and is pretty brittle too, so it's just going to be trouble nomatter what you do.

Another thing is the hysteresis effect. Acclimating a piece of wood from 60% down to 40% RH will still be more swollen than if it had gone from 20% up to 40%. This is why sometimes if you have a braced plate sitting out and your humidity level drops for a couple days, the plate goes concave and stays that way even after the humidity returns to normal. You need to take it up to high humidity and then back down to the shop level to restore it. But to prevent it happening in the first place, use a standard procedure of drying wood out and acclimating up before bracing.