So how close to 40-55% humidity should I be?

Discussions relating to the classical guitar which don't fit elsewhere.
Rasputin
Posts: 721
Joined: Fri May 12, 2017 12:25 pm

Re: So how close to 40-55% humidity should I be?

Post by Rasputin » Sat Feb 10, 2018 11:07 am

JohnB wrote:
Fri Feb 09, 2018 11:08 pm
Rasputin, with the humidipak system you have one humidipak (in a pouch) at the headstock, in addition to the soundhole pouches.

I've never had a humidipak leak but there have been reports on the web of it happening in the past. Mind you I take care with how I handle them and replace the packs every so often.
Thanks. That means it is really an in-case system though, so in practice it just wouldn't get used. The soundhole systems (the ones with a cover) create an enclosed space in the body of the guitar so you aren't losing all the moisture to the environment - but this means that the rest of the guitar doesn't get any love. I am probably overthinking it at this point and will just get a dampit and not worry unless the action suddenly changes. I don't suppose there is any harm in running a damp cloth up the back of the neck every few days - there is not really any glue around there and it won't get wet enough to go mouldy.

BTW I saw a review of the humidipak system which said you can rehydrate the packs by putting them in a sandwich box with a damp cloth, being careful that the two don't actually touch. Whether that affects the risk of leaks, I don't know.

JohnB
Posts: 694
Joined: Fri Jan 29, 2016 6:17 pm
Location: Bristol, UK

Re: So how close to 40-55% humidity should I be?

Post by JohnB » Sat Feb 10, 2018 11:49 am

I recharge the packs by placing them on a wire grid above a layer of water in a sealed plastic container and it takes 2 to 4 days. But there are many approaches with sponges etc. The basic method is to put the packs into a sealed high humidity environment, avoiding any direct contact with moisture.

The weight of the new packs I have used has been approx 72gm, so I recharge them back to that weight.

I've never had any leak. However the most vulnerable parts of the packs are the enclosing "envelope" which is likely to be gradually affected as the packs are repeatedly inserted and removed from the soundhole. So I replace the packs after a few recharges.
Hermanos Conde 1968, Stephen Frith 2007 "Guijoso"

soufiej
Posts: 47
Joined: Fri Jan 12, 2018 3:46 pm

Re: So how close to 40-55% humidity should I be?

Post by soufiej » Sat Feb 10, 2018 5:11 pm

"Follow up question - is the figure different for the neck and headstock, as compared to the body? I'm not in the habit of keeping my guitars in cases but realistically I suppose in-case humidification in the only way to get any moisture into the neck. I am thinking of getting a soundhole humidifier or more likely a dampit type humidifier and leaving it in overnight - once a week would probably be enough where I am now - but it won't do anything for the neck."


There is no different "figure" for the neck and headstock because you are still measuring the wrong value. You want to know the moisture content of the woods, not of the surrounding air. Since that value cannot be easily measured, for the average guitar owner it is safe to assume whatever safe R.H. value is surrounding the body is also sufficient for the neck and headstock.

Of course, that very statement says we still aren't measuring the moisture content of the body either, so we have a bit of a decision to make. Thus, the +/- 20% range given for the measured R.H in the room and at a location close to your guitar(s). Those are target values, not absolutes. Though, if the body of the guitar sits in a R.H. between 40 to 60% R.H,, then you could assume the neck is also at a value close enough for the safety of your instrument. Where the body goes, the neck must follow so ... (more on this later)

Consistency is far more important than just moisture. Consistent temperature and R.H. are needed to keep your guitar in top shape. If you've read this thread, you should catch on to the fact R.H. is a constantly fluctuating value which moves up and down every time your HVAC system runs. By changing the temperature of the air surrounding your guitar, you are also affecting the R.H. value. In case you didn't realize how an air conditioner operates, a technician will check your vents to make sure the air blowing into the room is approximately 20 degrees cooler than the existing air in the room. The opposite is generally true for the furnace. However, both systems create forced air entering the room that is less moist than the existing air.

Therefore, the most important thing you can do for your guitar is to place it in the room as far away from the HVAC vents (and the outside walls and windows) as possible to ensure consistency.

The moisture content of the woods is always seeking equilibrium with the R.H. value in the surrounding air, which in most forced air systems is always entering the room slightly less moist than the air within the room. If you are aware of the frequency and length of time your HVAC system runs, then you should have a good idea how often you should check your hygrometer. Just don't get overly concerned with any one reading, consistency within the desired range over time is the key.




"The soundhole systems (the ones with a cover) create an enclosed space in the body of the guitar so you aren't losing all the moisture to the environment - but this means that the rest of the guitar doesn't get any love. I am probably overthinking it at this point and will just get a dampit and not worry unless the action suddenly changes. I don't suppose there is any harm in running a damp cloth up the back of the neck every few days - there is not really any glue around there and it won't get wet enough to go mouldy."



Consider the various woods used in a guitar and the amount of exposed grain. More dense woods tend to have a higher oil content which acts to keep the material at a proper moisture value. Spruce, rosewood, cedar and mahogany all have different oil contents and, therefore, all require a different preferred R.H. value to maintain their "seasoned" tonal qualities. You cannot be concerned with each and every small area of your guitar when it comes to moisture, which is why you have a broad range of R.H. values to work from.

While it may cause no harm to your guitar to run a "damp" cloth up the neck, it will certain do nothing to protect the neck in terms of moisture content. All points on the neck other than the exposed end grain at the body/neck joint are sealed with some form of protective material. Even if this were not the case, the moisture from the cloth would only be penetrating the top few tenths of an inch into the wood of the neck. That's certainly not going to change the neck wood's total moisture content.

It was mentioned that there isn't much to concern yourself with unless the action of the neck rapidly changes. That too is missing the point. Neck angle is different from neck relief yet both affect the height of the strings above the neck. Of course, the cut of the string slots in the nut and the height of the saddle above the bridge also add to the action of the guitar. Assuming the nut and saddle are set comfortably at this time, then it is the neck angle which is most commonly the cause of a rising action.

However, most people mistake what is happening with the neck as being only neck issues. If the neck is not bowing or warping, then the relative neck angle is first affected by changes in the body materials. If the lower bout begins to belly, the bridge is likely to lift which will raise the saddle and the angle the saddle strikes the strings. Likewise, if the bout begins to sink, the saddle must follow. Movement in either direction will affect the action of the strings, and the intonation of the guitar, due to the changes in the neck angle relative to these parts of the body. If the goemetric changes have become permanent, many techs will suggest shaving the saddle or the nut slots to return the proper string height above the fretboard. With this sort of quick fix, the trade off is against proper intonation. Eventually, the saddle has no more adjustment available and then a neck reset is the most common repair.

This is NOT the proper technique for achieving a neck reset; https://www.youtube.com/watch?v=K1H4xy52RuM

If the upper bout begins to sink, the sides and back of the guitar typically follow the movement of the top, which is likely to change the physical length of the guitar. If the back flattens, the same dimensional changes will occur. All of these changes in the geometry of the guitar's body will ultimately affect the guitar's neck angle. Small changes in geometry occur almost constantly and are not to be considered a danger to the guitar any more than the fact your all wood table is changing by 0.05" should bother you.

However, if the neck angle changes dramatically or if the bridge begins to lift from its rear point connection to the body, then you should have the guitar attended to by a qualified technician. Loose or broken braces may also account for these same changes though the most likely cause is neglecting the consistency of the temperature and humidity values surrounding your guitar. Glues deteriorate in extreme heat and cold as well as moist and dry conditions so don't leave your guitar in your car or in a damp, cool basement/hot, dry attic.

In case you haven't figured out exactly what changes the neck angle, it is not the moisture content of the woods in the neck itself. The neck follows changes in the body geometry. Therefore, concerning yourself with moisturizing the neck is missing the point. Keep the guitar in a R.H. which is consistent, not too high nor too low for days on end, and your guitar will be happy. Make changes to the temperature and the moisture content of the surrounding air slowly thus allowing your guitar to acclimate to its new environment. You have a broad +/- 20% value to work with and the guitar will likely survive much higher and much lower values for days before the thin woods of the body begin to change.

Play your guitar regularly and become accustomed to the tonal qualities of your guitar when it is slightly moist and slightly dry. Use your ears to detect problems before they become serious. That's the "love" your guitar needs.

Rasputin
Posts: 721
Joined: Fri May 12, 2017 12:25 pm

Re: So how close to 40-55% humidity should I be?

Post by Rasputin » Sat Feb 10, 2018 6:20 pm

soufiej wrote:
Sat Feb 10, 2018 5:11 pm
"Follow up question - is the figure different for the neck and headstock, as compared to the body? I'm not in the habit of keeping my guitars in cases but realistically I suppose in-case humidification in the only way to get any moisture into the neck. I am thinking of getting a soundhole humidifier or more likely a dampit type humidifier and leaving it in overnight - once a week would probably be enough where I am now - but it won't do anything for the neck."


Consistency is far more important than just moisture. Consistent temperature and R.H. are needed to keep your guitar in top shape.
Yes, but don't forget that that the moisture content of the wood at the time it was glued is a fixed value. The more the current value deviates from that, the more the shape of the guitar will deviate from the shape the luthier intended. Of course a bit of deviation is OK, but after a while the performance of the guitar is going to be affected, and eventually you will get cracking or warping, or the glued joints will fail - so it's not just a question of consistency, you also want to make sure you don't stray too far from the original values. As has already been pointed out, keeping track of RH is a good enough way of keeping track of the moisture content of the wood, even though the two things are not the same.

"The soundhole systems (the ones with a cover) create an enclosed space in the body of the guitar so you aren't losing all the moisture to the environment - but this means that the rest of the guitar doesn't get any love. I am probably overthinking it at this point and will just get a dampit and not worry unless the action suddenly changes. I don't suppose there is any harm in running a damp cloth up the back of the neck every few days - there is not really any glue around there and it won't get wet enough to go mouldy."


Consider the various woods used in a guitar and the amount of exposed grain. More dense woods tend to have a higher oil content which acts to keep the material at a proper moisture value. Spruce, rosewood, cedar and mahogany all have different oil contents and, therefore, all require a different preferred R.H. value to maintain their "seasoned" tonal qualities.
Hence my question. In my world it is not feasible to keep the whole room within range, or even part of the room. The guitar will be drying out most of the time and will need to have its moisture levels topped up regularly so that this doesn't become a problem. The point about the neck is that while it is practical to feed moisture into the body cavity, in reality the visible part of the neck is never going to be in moist air. For this reason it is necessary to consider different parts of the guitar separately.
While it may cause no harm to your guitar to run a "damp" cloth up the neck, it will certain do nothing to protect the neck in terms of moisture content. All points on the neck other than the exposed end grain at the body/neck joint are sealed with some form of protective material. Even if this were not the case, the moisture from the cloth would only be penetrating the top few tenths of an inch into the wood of the neck. That's certainly not going to change the neck wood's total moisture content.
There is a finish on it, for sure - whether it is water-permeable is another matter. If it isn't then what you say is right, and the short answer is that the only way to get moisture into the neck is though the body cavity anyway. That still leaves the fingerboard though - that would still be drying out. That is probably where the damp cloth treatment is needed.
It was mentioned that there isn't much to concern yourself with unless the action of the neck rapidly changes. That too is missing the point. Neck angle is different from neck relief yet both affect the height of the strings above the neck. Of course, the cut of the string slots in the nut and the height of the saddle above the bridge also add to the action of the guitar. Assuming the nut and saddle are set comfortably at this time, then it is the neck angle which is most commonly the cause of a rising action.
It doesn't matter what the most common cause is - the point is that the body of the guitar will be fine and dandy but it is possible that the neck (or fingerboard) may dry out. I will just have to look for signs of this whether it is in the shape of the neck, or problems with the frets, or whatever.

soufiej
Posts: 47
Joined: Fri Jan 12, 2018 3:46 pm

Re: So how close to 40-55% humidity should I be?

Post by soufiej » Sun Feb 11, 2018 1:20 am

"Yes, but don't forget that that the moisture content of the wood at the time it was glued is a fixed value. The more the current value deviates from that, the more the shape of the guitar will deviate from the shape the luthier intended. Of course a bit of deviation is OK, but after a while the performance of the guitar is going to be affected, and eventually you will get cracking or warping, or the glued joints will fail - so it's not just a question of consistency, you also want to make sure you don't stray too far from the original values. As has already been pointed out, keeping track of RH is a good enough way of keeping track of the moisture content of the wood, even though the two things are not the same."


A "bit of deviation"? What's "a bit"? You have a 20% range and there will not be any immediate danger to the guitar if the values move outside of that range temporarily. The woods will not be affected for days to weeks of sustained R.H. values well below or above the suggested range.

Don't get O.C.D about this. Consistency IS the key. Consistency in the woods, which you cannot measure. The rest is just guess work and common sense.

Woods take a long time to change their moisture content. What happens with R.H. values is a constantly changing march up and down all day and night while the guitar requires days and weeks to change. If you do not abuse the guitar, neck problems with nylon string guitars are minimal.

Most factory built guitars are constructed to withstand significant changes in environment during shipping and storage. If your guitar has managed to stay together during a trip from one coast to the other inside a tractor trailer (or across the globe in the cargo area of a jet flying at 30k feet) and then storage in a warehouse for weeks, there's really not much you can do, other than out and out abuse, which will cause significant and lasting damage to your guitar.

If you have a more expensive - and more lightly constructed - luthier built guitar, consult the builder.

The R.H. is not really a way of keeping track of the moisture content of the woods. Spruce has a different oil content than does cedar. You can't give each part of the guitar individual attention. You have a very broad range of values to work with but if you check your hygrometer in the AM after a cold night, the HVAC system will have dried out the air in the room. If it's going to warm up that day and rain is in the forecast, then the hygrometer will begin to reflect the changes the larger environment has on the interior of the room. You can check the meter hourly if you like but all you'll find out is the R.H being measured is very volatile. The woods in your guitar are not. You can't moisturize just the rosewood bridge and that is one of the first places to show environmental neglect. R.H and wood moisture ARE NOT the same thing and the former should not be interpreted to reflect the values of the latter.


"Hence my question. In my world it is not feasible to keep the whole room within range, or even part of the room. The guitar will be drying out most of the time and will need to have its moisture levels topped up regularly so that this doesn't become a problem. The point about the neck is that while it is practical to feed moisture into the body cavity, in reality the visible part of the neck is never going to be in moist air. For this reason it is necessary to consider different parts of the guitar separately."


You don't need the "whole room" humidified. You want the area surrounding your guitar(s) to be within the very broad range allowed. Your reasoning says you're looking for ways to make this more difficult than it needs to be.

There is no such thing as "topping up" the moisture levels of the woods. Consistency is the key, not "topping up". You are completely missing the point of humidifying the body of the guitar to protect the structure of the guitar. You don't need to moisturize the neck. You don't need to moisturize the headstock. You don't need to moisturize the bridge. You need to practice consistency in the environment the guitar body experiences. Period! And to play your guitar and become aware of the changes moisture will have on the tonal balance of the guitar. The string tensions on a nylon string guitar are minimal compared to its steel string cousin. If you have a well built guitar, just tuning it should give you some idea of how consistent the guitar is. If you don't have to retune a played in string set by a full step, the body has not undergone significant changes. Just play your guitar, that's the easiest way to understand what's occurring with the guitar.




"It doesn't matter what the most common cause is - the point is that the body of the guitar will be fine and dandy but it is possible that the neck (or fingerboard) may dry out. I will just have to look for signs of this whether it is in the shape of the neck, or problems with the frets, or whatever."


Of course it matters what the most common causes are! The neck is essentially sealed and cannot easily accept or lose moisture in a short amount of time. Is the neck cedar? Or, mahogany? Both woods are dense and filled with oils. They are also cut in a manner that does not expose a large amount of grain to the surface. The body woods are cut in a manner (typically quartersawn) that exposes large amounts of grain to the environment, which makes it more susceptible to losing, retaining or gaining moisture from the environment. If the body is OK, there are such slim chances the neck is not that worrying about it is like constantly wondering when the world will end.

If you are comfortable in the room's humidity with your guitars, then the neck is OK too. Rubbing a damp cloth along any part of the neck is not going to change the overall moisture content of the wood. It's like thinking you can rub a damp cloth on the hood of your car to add water to the radiator.

Are you rubbing the finger board with a bit of oil when you change strings? That's all it needs and only about once a year at that. Do not think of moisture in terms of water, the dense woods of the neck and fingerboard will benefit from supplemental oils.

Apply enough oil to lightly cover the fingerboard and use the oiled cloth to clean around the frets once per year when you change strings. Let the fingerboard absorb the oil for about five minutes and then thoroughly wipe away the residual. That's all you need to do once per year. Do not apply water to the ebony or rosewood fingerboard.

Don't over think this.

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