Humidity Issues with Martin Acoustic Guitar
 

Hello,

I am the proud owner of a Martin OMJM, but have been experiencing some frustrating issues that are diminishing the joy of guitar ownership.

I recently had the instrument set up by a professional luthier as it did not feel as good as it used to. He informed me that the guitar was affected by excess humidity. So, before bringing it home I purchased a dehumidifier and ensured that my basement studio was ideal for the instrument.

I then picked up the guitar and, in the shop, it felt amazing! Just as nice as the day I bought it.

However, after a few days of being back in my basement studio, the guitar neck became extremely bowed, the action raising to an unplayable level. Once again, it exhibited all the symptoms of an overly humid guitar.

I lowered the dehumidifier even more, set up a heater to make the room warmer and drier, kept the guitar in the case, and even purchased D’Addario’s Humiditrak Humidity Control system for inside the Martin’s case. After several weeks of keeping the humidity and temperature in the ideal range, the guitar has shown no improvement and still exhibits all the symptoms of a humid guitar (bowed neck, high action, dull tone and warped back).

My room is at about 44% Humidity and 23 Degrees Celsius. This is supposedly the ideal environment but the guitar is unplayable!

I’m thinking of purchasing an Acoustic Humidor from Acoustic Remedy Cases, but I’d like to get some suggestions before making that pricey investment.

Thanks in advance,
Tyler

It seems that your readings of the environment may not be accurate and it’s hanging in the 50%++ range. Most Basements are usually not ideal environments for wood.


Are your hygrometers calibrated?

Thanks for your response! My hygrometers have not been calibrated, so I’m going to do so now using the Salt Method. Hopefully this will give me a more accurate reading.

I’ll have to consider moving my guitar out of my basement studio as the dehumidifier is currently on the lowest setting.

Thanks!

I’ve always believed that it’s dryness that causes increased neck-relief, and excess humidity reduces relief. I’ve been trying to find where I read that but no luck so far. So, if the OP’s neck actually has ‘bowed’, i.e. taken on increased relief, it would suggest his guitar may be too dry rather than too wet. It would help if we knew what relief is in the neck (in thousandths of an inch).

I’m wondering if it’s more the case that over-humidification has caused the guitar’s top to belly, resulting in higher 12th fret action and a change in the neck’s geometry with the body rather than an actual ‘bow’ in the neck. If that’s the case, no amount of swinging on a truss-rod wrench will fix it because it’s not a relief problem.



The usual disclaimers apply......IMHO, YMMV etc.

Tyler - Welcome to the AGF!

Sounds like humidity issues. Not sure where you live but basements tend to have lots of dampness. Nothing a good dehumidifier can't handle though.

How big is your studio? Do you keep the door closed to help keep it climate controlled? Also, make sure you dehumidifier can handle the square footage and that it is actually working.

If the neck is "extremely bowed", what is the current neck relief measurement? Has it increased to an unacceptable amount?

It's more likely that the top has bellied causing the bridge to rise increasing the action height.

Moisture content induced longitudinal shrinkage/lengthening (neck length change) of wood is about 0.1% to 0.2% compared to 3.2% for radial shrinkage/lengthening (across the top) for spruce. That's why the top belly change is the more likely cause.

Getting back to a reference point
 

Is the neck truly bowed or are you assuming that because of the high action? What usually reacts faster to high humidity is the top -- bellying out. Check it first, if you have some referenda point to do so, or ask your luthier what is typical side--to-side belly. A truss-rod reinforced neck is not likely to move so much because of humidity to where it causes an unplayable higher action.

Also, the whole term for humidity is relative humidity -- relative to the temperature. If I were to get a guitar to dry out, I would cool the room, not heat it. Warm air holds much more humidity than cold air. I had a dehumidifier in my basement (800 sf) and during the summer it pulled a full gallon of water out of the air every day. You need something like that to get some normative humidity and use Humidipaks to fine-tune.

Finally, Humidipaks, in my experience, are good for discharging water vapor not not as good a absorbing it. Either way, they are not all that precise given all the other variables.

If your guitar really absorbed that much moisture, it may take weeks for it to get re-stablizied. Yup don't want to rush it.

Relative humidity is not relative to temperature, per se. It is relative to how much moisture air can hold at that temperature. The amount that it can hold is temperature dependant, but the relative humidity is a ratio of how much moisture there is in the air compared to how much there could be, at that given temperature.


No, you would heat it to lower the relative humidity. If you have the same quantity of moisture (absolute humidity) - not adding or removing moisture - raising the temperature - increasing its potential, how much it can hold - will increase. Doing so will lower the relative humidity, since the amount of moisture stays the same but the amount it can hold increases. The relative humidity - amount of moisture in the air/amount of moisture the air can hold - decreases.

If by salt you mean sodium chloride you would be better off using potassium carbonate. Table salt can be used to calibrate to a RH of 75%, whereas potassium carbonate equilibrates at 43%, which is much closer to where you want to calibrate your hygrometer. You can order potassium carbonate on Amazon, and find the calibration methods with a google search.

Just curious. You hanging you're guitar on the wall? Keeping in a stand? Or keeping in the case? Whichever is the case. I'd move it out of the basement.

Welcome to the forum.

I don't think that D'Addario's humidipack system works as effectively at drying things out as it does at preventing dryness. My experience as someone who lives on or near the water in the Pacific Northwest suggests that other forms of desiccant packs will be more effective.

I just wouldn't ever store a guitar in a basement, even within a case. In my cabin in the San Juan Islands, I keep guitars up in the loft, the driest place I have, especially in the winter when we keep the wood stove fired up. Regardless, running a dehumidifier in a basement while the guitar is stored in a case seems a bit futile.

Is this the in-case RH gauge with or without a Bluetooth transmission system? When I first read your post, I took it to means the gel filled Humid-paks. They are pretty good at adding moisture to a dry case, but do a poor job of absorbing excess humidity beyond their set point - unless they are already dry to the point of being crunchy.

I don't use the salt test to check the accuracy of my hygrometers. I put them outside for a few hours and compare them to the official aviation weather reports. The NWS weather station is at the airport 3 miles from my house. Even so we water the large lawn so our outdoor RH is often ~5 points higher than the official number.

We may be saying the same thing, but relative humidity is determined by temperature in that the temperature affects how much vapor the air can hold. Cold air tends to have lower vapor levels -- this is how humidifiers work. Higher temperatures can hold more moisture because the water in the air more easily vaporizes. My point to the poster is that a warm basement -- given the same amount of moist air entering the environment -- will have a lot more water vapor suspended than a cold one. With a given (absolute) amount of moisture, the warm air will hold more than the cold, thus exposing the guitar to more water vapor and slowing evaporation.

The goal here is to reduce the amount of vapor (suspended moisture) in the atmosphere of his basement.

However we may disagree, he likely needs a room humidifier to create a more stable baseline for the humidity level he needs.

There's something else going on here?
 

My guitar room is a 71% RH at 19 deg C at present. It has been over 70% RH for a couple of months. The necks on my guitars haven't moved. The action on my guitars hasn't moved.

There's something else going on here, not just humidity issues. There is something structurally not right. But without seeing the guitar I couldn't say what it was. A guitar shouldn't be moving that much that quickly unless there is a significant structural weakness (young woods fast dried, thin sides badly sawn, poor bracing etc).

This is an expensive guitar; to be displaying such instability is just plain wrong!

45% - 55% is fine, ideal actually, and so are basements if they are climate controlled and monitored.