NAGD - Martin - what did i do?

[Embenny]

One of the things that deceives people has to do with the "relative" part of Relative Humidity.

Just like any solute/solvent combo, more water can dissolve into air when it's warm than when it's cold. Unfortunately, your guitars don't care about the absolute amount of water dissolved in air, just the relative amount. If the RH of the air around the wood is lower than the wood itself, it starts evaporating water into its environment, and likewise absorbs it when the RH is higher than the wood's humidity.

The relative amount is expressed as a percentage of the current amount of water divided by the holding capacity of the air.

Let's say it's 40F/4C outside and pouring rain. The outdoor relative humidity is 100% because the air is soaked with as much water as it can hold, which is 5g/kg.

But then let's say you take that air into your house and heat it to 70F/21C. That 100% RH outdoor air contains the exact same quantity of water, but the holding capacity triples from 5g/kg to 15g/kg. So now the air has 5/15 = 33% RH, which is now low enough to potentially damage a guitar over the long term, despite what seems like a very warm and wet winter outside.

The opposite happens when you cool hot air. If you took 100% RH air at 70 degrees and cooled it to 40, 2/3rds of that moisture would precipitate out of the air as condensation. That's why there's dew on everything after a cool night when it's humid outside.

Your house has several sources of humidity, mostly the moisture you transpire, but potentially other things as well like wet laundry you've hung to dry, open aquariums, a damp basement with ground water leaking in, etc. Modern "tight" homes have very little air leakage, to the point that you need an air exchanger to move stale humid air out and bring fresh dry air in during the winter, but "leaky" older homes are constantly losing indoor air and having outside air drafting in.

It all comes down to a balance of air in vs air out, heating vs cooling the air (which is why air conditioners dehumidify air and drain out the condensation that's formed), and how many sources of humidity you have in the house.

That's how you can live somewhere you consider to be a humid place, but end up with very dry indoor air. It might be 40 degrees and raining outside all winter, but the second you heat that air up without adding moisture via a central or room humidifier, you're not living in such a humid place anymore. Hell, I keep my entire house at 37-42%RH and thought I was safe, but I had a small storage unit in my furnace room with a guitar neck in it that developed fret sprout because I failed to realize that the heat radiated by my furnace made that room about 5 degrees warmer than the rest of the basement all winter, and the RH was therefore over 10% lower.

This is also why it's great to keep guitars in cases during the winter. If you hit a cold spell and the humidity drops, or a humidifier runs dry for a day or two without you noticing, the dry air has to diffuse through a sealed case in order to reach and dry out your guitar. It prolongs the time scale of the expansion and contraction of the wood and smoothes short spikes and drops in RH. Also, if the case is made of wood, the wood of the case itself acts as a humidity reservoir. When things get dry, the case loses moisture and keeps the guitar in a more humid micro-climate for a period of time.

That's also why, when you first turn on a humidifier in a dry house, the tank runs empty super fast. Every hygroscopic (water-absorbing) material in your room is soaking up that water as you put it into the air - floors, furniture, walls. But once you reach an equilibrium at 40% or whatever RH, all those materials are now like a moisture holding tank. If the humidifier runs dry, all those objects start losing moisture and the drop in the RH of your air is much, much slower as a result. I'm in an airbnb apartment while my house is being sold, and it was ~5% RH in here when we arrived (yes, 5% - old, drafty building, Canadian winter, radiators for heating). My console humidifier put out 3 gallons of water into the air of this ~700 square foot apartment in the first day to reach and maintain 42% RH. A week later, it's doing about 3/4 of a gallon a day to maintain 42% RH, because the door frames, wall studs, and furniture have just about equilibrated at 42% and are no longer acting like dry sponges.

I'm a science nerd and an acoustic guitar nerd, so I'm sorry if this is TMI. I love this stuff and have read about it a lot and experimented a lot ever since my catastrophic Taylor implosion incident.

[Drill]

Will continue the off topic:

1) I just found an hygrometer app, it should help or it's fake news?
2) My house has leakage all over, so it must be quite balanced right?
3) What's good for your guitars is not good for your amps? Where I am we usually have way more problems with humidity (buying storaged old amps that smell...). I bought an amp that was consistently giving problems until I bought a dehumidifier (that room where I kept it frequently had black spots on the wall).
4) In Germany it's mandatory to open your windows 2x a day during winter (in rented houses) because if you don't the houses get all wet and start to ruin everything. They definitely warm their houses with central heating gas system. So I find your experiences quite surprising.

[Embenny]

Will continue the off topic:

1) I just found an hygrometer app, it should help or it's fake news?
2) My house has leakage all over, so it must be quite balanced right?
3) What's good for your guitars is not good for your amps? Where I am we usually have way more problems with humidity (buying storaged old amps that smell...). I bought an amp that was consistently giving problems until I bought a dehumidifier (that room where I kept it frequently had black spots on the wall).
4) In Germany it's mandatory to open your windows 2x a day during winter (in rented houses) because if you don't the houses get all wet and start to ruin everything. They definitely warm their houses with central heating gas system. So I find your experiences quite surprising.

1) A hygrometer app either needs a phone with a hygrometer built in, a hygrometer synced wirelessly, or might simply display outdoor humidity.

2) Generally, air leakage plus cold weather plus heating = low humidity. Air leakage plus warm weather = high humidity, but lots of factors individual to a home can break the general trend.

3) Incorrect. 40% RH is great for guitars and great for electronics. 40% will never cause rusting of metal or rotting of wood cabinets, and actually cuts down on static electricity that can harm sensitive electronics. The humidity problems you're describing are from excessive humidity, which is as bad for a guitar as it is for and amp or your house or your health (you're describing black mold growing on walls - this is extremely dangerous to your health. Move if you rent and you can, and if you own the place, please consult a professional for help eradicating and controlling it). You're correct to dehumidify such an environment, as the indoor humidity was probably 90-100% to be causing those problems and absolutely needs dehumidifying.

4) It sounds like the housing construction standards in Germany are probably very "tight", then. It has to do with things like what type of membranes are used in the walls during construction and how they address the connection point between walls and floors. If a house is built tight, then yes, during the winter, you can absolutely end up with too much humidity because all the moisture the residents are transpiring has nowhere to go. Or, enough houses are built tight that they give everyone those instructions in order to prevent things like the black mold you described from growing, since a moldy house is far more dangerous to human health than an overly dry one.

That's why I described indoor humidity as a balance between sources of moisture and sources of fresh, dry air. You can easily have a dry house during a wet summer if you air condition in a tight home, and you can easily have a wet one in during a dry winter if you heat a tight home. You can also have perpetual sources of moisture like a basement with groundwater leaking in. There are so many factors that you can't ever presume that humidifying or dehymidifying is the right move without simply measuring it, which can be done on an ongoing basis for all of $20.

[Drill]

Will continue the off topic:

1) I just found an hygrometer app, it should help or it's fake news?
2) My house has leakage all over, so it must be quite balanced right?
3) What's good for your guitars is not good for your amps? Where I am we usually have way more problems with humidity (buying storaged old amps that smell...). I bought an amp that was consistently giving problems until I bought a dehumidifier (that room where I kept it frequently had black spots on the wall).
4) In Germany it's mandatory to open your windows 2x a day during winter (in rented houses) because if you don't the houses get all wet and start to ruin everything. They definitely warm their houses with central heating gas system. So I find your experiences quite surprising.

1) A hygrometer app either needs a phone with a hygrometer built in, a hygrometer synced wirelessly, or might simply display outdoor humidity.

2) Generally, air leakage plus cold weather plus heating = low humidity. Air leakage plus warm weather = high humidity, but lots of factors individual to a home can break the general trend.

3) Incorrect. 40% RH is great for guitars and great for electronics. 40% will never cause rusting of metal or rotting of wood cabinets, and actually cuts down on static electricity that can harm sensitive electronics. The humidity problems you're describing are from excessive humidity, which is as bad for a guitar as it is for and amp or your house or your health (you're describing black mold growing on walls - this is extremely dangerous to your health. Move if you rent and you can, and if you own the place, please consult a professional for help eradicating and controlling it). You're correct to dehumidify such an environment, as the indoor humidity was probably 90-100% to be causing those problems and absolutely needs dehumidifying.

4) It sounds like the housing construction standards in Germany are probably very "tight", then. It has to do with things like what type of membranes are used in the walls during construction and how they address the connection point between walls and floors. If a house is built tight, then yes, during the winter, you can absolutely end up with too much humidity because all the moisture the residents are transpiring has nowhere to go. Or, enough houses are built tight that they give everyone those instructions in order to prevent things like the black mold you described from growing, since a moldy house is far more dangerous to human health than an overly dry one.

That's why I described indoor humidity as a balance between sources of moisture and sources of fresh, dry air. You can easily have a dry house during a wet summer if you air condition in a tight home, and you can easily have a wet one in during a dry winter if you heat a tight home. You can also have perpetual sources of moisture like a basement with groundwater leaking in. There are so many factors that you can't ever presume that humidifying or dehymidifying is the right move without simply measuring it, which can be done on an ongoing basis for all of $20.

This is public service right here man! There are no likes or golds, but you surely would deserve all of that

[MKR]

I agree. Mbene, you have provided some real insight.

[Larry Mal]

I can't add anything intelligent to what Mike said, except I'll mention that if you are seeing moisture on your walls, you have almost certainly overhumidified.

And I'm sure it's been beaten into everyone's head at this point, but everyone should have a hygrometer just for basic human maintenance, whether or not one owns a fancy-ass acoustic guitar.

[beninma]

Lots of good insights in this thread.

I have had issues with humidity in the past and am super fastidious about it. If you are ever skeptical note that pretty much every manufacturer really wants you to take care of the humidity problem. I have a Taylor they put pamphlets in the case making it crystal clear they want you addressing humidity.

My house was built in 2006, relatively new, expensive construction (northeast) fancy windows, energy star rated 98 condensing furnace + forced hot air.

We bought the house in 2010. The house was dry as heck in the winter. Forced hot air heat just does this. Our RH in the house in the winter would be less than 20%. To the point it affects your health, electronics problems, tons of static shocks.

Room humidifiers don't do much in this situation. You really need a humidifier that has a fixed water line so it can pump tons of water. Personal experience both ways really.

Since I started playing guitar I had an issue with one of my first acoustic guitars due to the dry interior of the house. Between that and the room humidifiers getting quite scary from mold growth + the constant cleaning we spent ~$1000 on a unit installed into the furnace to re-humidify the air.

Let me put it this way, the unit on the furnace can put 21 gallons per day into the air. That would have been a LOT of refilling of the room humidifiers.

And I still can't get the area where I play my guitars up to 40% right through the winter, it's not safe for the house. If it's 20 degrees outside and you humidify the interior to 45% for your guitar you'll get condensation in the house and can end up with mold or damage. Fancy furnace units have a computer and an exterior + interior temperature sensor setup that automatically lowers the internal humidity of the house for safety. Mine really won't get the house to 40%+ relative humidity until the outside air is 40F+.

The best thing is to keep the guitars in a hardwood case with humdity control. They cost money but I love the Daddario Humidpaks.

I just got a Reverend, it shipped from Colorado and it has fret sprout, possibly just from shipping. I have it in the hard case with humidipaks, I'm hoping that' all it takes. Awesome guitar otherwise.

Regarding finish I *love* these thin Satin finishes on acoustic guitars. Glossy finish is super "meh" IMO. On an acoustic a thin satin finish that's barely there just screams quality to me and it also always seems to stay so clean. My Taylor has one of these finishes and the guitar just stays so clean compared to my glossy electrics. My previous acoustics were cheaper guitars and they had the thick glossy finishes.. those seem cheesy to me now.

Particularly when the guitar is made in Asia and shipped halfway across the planet that's pretty tough on the wood. Big humidity changes along the way. If you've got a MIM or MIA guitar made in CA it's shipping from a dry area and the manufacturer is keeping the interior of the factory humidified and it doesn't have to travel so far.

[Drill]

One of the things that deceives people has to do with the "relative" part of Relative Humidity.

Just like any solute/solvent combo, more water can dissolve into air when it's warm than when it's cold. Unfortunately, your guitars don't care about the absolute amount of water dissolved in air, just the relative amount. If the RH of the air around the wood is lower than the wood itself, it starts evaporating water into its environment, and likewise absorbs it when the RH is higher than the wood's humidity.

The relative amount is expressed as a percentage of the current amount of water divided by the holding capacity of the air.

Let's say it's 40F/4C outside and pouring rain. The outdoor relative humidity is 100% because the air is soaked with as much water as it can hold, which is 5g/kg.

But then let's say you take that air into your house and heat it to 70F/21C. That 100% RH outdoor air contains the exact same quantity of water, but the holding capacity triples from 5g/kg to 15g/kg. So now the air has 5/15 = 33% RH, which is now low enough to potentially damage a guitar over the long term, despite what seems like a very warm and wet winter outside.

The opposite happens when you cool hot air. If you took 100% RH air at 70 degrees and cooled it to 40, 2/3rds of that moisture would precipitate out of the air as condensation. That's why there's dew on everything after a cool night when it's humid outside.

Your house has several sources of humidity, mostly the moisture you transpire, but potentially other things as well like wet laundry you've hung to dry, open aquariums, a damp basement with ground water leaking in, etc. Modern "tight" homes have very little air leakage, to the point that you need an air exchanger to move stale humid air out and bring fresh dry air in during the winter, but "leaky" older homes are constantly losing indoor air and having outside air drafting in.

It all comes down to a balance of air in vs air out, heating vs cooling the air (which is why air conditioners dehumidify air and drain out the condensation that's formed), and how many sources of humidity you have in the house.

That's how you can live somewhere you consider to be a humid place, but end up with very dry indoor air. It might be 40 degrees and raining outside all winter, but the second you heat that air up without adding moisture via a central or room humidifier, you're not living in such a humid place anymore. Hell, I keep my entire house at 37-42%RH and thought I was safe, but I had a small storage unit in my furnace room with a guitar neck in it that developed fret sprout because I failed to realize that the heat radiated by my furnace made that room about 5 degrees warmer than the rest of the basement all winter, and the RH was therefore over 10% lower.

This is also why it's great to keep guitars in cases during the winter. If you hit a cold spell and the humidity drops, or a humidifier runs dry for a day or two without you noticing, the dry air has to diffuse through a sealed case in order to reach and dry out your guitar. It prolongs the time scale of the expansion and contraction of the wood and smoothes short spikes and drops in RH. Also, if the case is made of wood, the wood of the case itself acts as a humidity reservoir. When things get dry, the case loses moisture and keeps the guitar in a more humid micro-climate for a period of time.

That's also why, when you first turn on a humidifier in a dry house, the tank runs empty super fast. Every hygroscopic (water-absorbing) material in your room is soaking up that water as you put it into the air - floors, furniture, walls. But once you reach an equilibrium at 40% or whatever RH, all those materials are now like a moisture holding tank. If the humidifier runs dry, all those objects start losing moisture and the drop in the RH of your air is much, much slower as a result. I'm in an airbnb apartment while my house is being sold, and it was ~5% RH in here when we arrived (yes, 5% - old, drafty building, Canadian winter, radiators for heating). My console humidifier put out 3 gallons of water into the air of this ~700 square foot apartment in the first day to reach and maintain 42% RH. A week later, it's doing about 3/4 of a gallon a day to maintain 42% RH, because the door frames, wall studs, and furniture have just about equilibrated at 42% and are no longer acting like dry sponges.

I'm a science nerd and an acoustic guitar nerd, so I'm sorry if this is TMI. I love this stuff and have read about it a lot and experimented a lot ever since my catastrophic Taylor implosion incident.

Just wanted to say that finally I took the matter into my own hands and bought an hygrometer (I bought one when this topic came on, but came broken and never bothered to buy another).

This one I thought it was also a dud, because I made the salt test and it was a bit all over the place. But placed a bit more water, opened and closed the bag and the next day it came 75%. So I think it's pretty accurate. Will repeat it.

However it has always said that the humidity in my studio was around 65% (before and after the test) so when I thought I had a dry division, I had in fact a humidity problem. (I just bought distilled water and a supersonic humidifier because I couldn't find a cold myst one... guess I won't be needing it).

All because I was feeling my allergies coming back. Let's see if it improves...

[Embenny]

Just wanted to say that finally I took the matter into my own hands and bought an hygrometer (I bought one when this topic came on, but came broken and never bothered to buy another).

This one I thought it was also a dud, because I made the salt test and it was a bit all over the place. But placed a bit more water, opened and closed the bag and the next day it came 75%. So I think it's pretty accurate. Will repeat it.

However it has always said that the humidity in my studio was around 65% (before and after the test) so when I thought I had a dry division, I had in fact a humidity problem. (I just bought distilled water and a supersonic humidifier because I couldn't find a cold myst one... guess I won't be needing it).

All because I was feeling my allergies coming back. Let's see if it improves...

If, in fact, your indoor RH is 65% in winter, there's a chance your indoor allergies are due to mold, not dry sinuses. If you have a basement, check the RH there. My parents had an old house that was usually 40-50% RH upstairs, but 80-100% RH in the basement, which doesn't discourage mold growth, let me tell you that. Also, people spend more time indoors during winter and dust might be triggering the indoor allergy.

[Drill]

Just wanted to say that finally I took the matter into my own hands and bought an hygrometer (I bought one when this topic came on, but came broken and never bothered to buy another).

This one I thought it was also a dud, because I made the salt test and it was a bit all over the place. But placed a bit more water, opened and closed the bag and the next day it came 75%. So I think it's pretty accurate. Will repeat it.

However it has always said that the humidity in my studio was around 65% (before and after the test) so when I thought I had a dry division, I had in fact a humidity problem. (I just bought distilled water and a supersonic humidifier because I couldn't find a cold myst one... guess I won't be needing it).

All because I was feeling my allergies coming back. Let's see if it improves...

If, in fact, your indoor RH is 65% in winter, there's a chance your indoor allergies are due to mold, not dry sinuses. If you have a basement, check the RH there. My parents had an old house that was usually 40-50% RH upstairs, but 80-100% RH in the basement, which doesn't discourage mold growth, let me tell you that. Also, people spend more time indoors during winter and dust might be triggering the indoor allergy.

Yeah, dust sucks and my house seems to have an infinite ammount of it (Guess it's all houses but... if anyone has any revolutionary tip I would be forever grateful).

65% is enough to grow mold? I read that more than 60% is enough to cause allergies. But mould I find it very unlikely. I feel like this house I live in is one of the driest I've been in (counting family, friends and all that).

The only problem is the air leakage through the wooden windows That doesn't help to maintain the humidity levels.

[Embenny]

If, in fact, your indoor RH is 65% in winter, there's a chance your indoor allergies are due to mold, not dry sinuses. If you have a basement, check the RH there. My parents had an old house that was usually 40-50% RH upstairs, but 80-100% RH in the basement, which doesn't discourage mold growth, let me tell you that. Also, people spend more time indoors during winter and dust might be triggering the indoor allergy.

Yeah, dust sucks and my house seems to have an infinite ammount of it (Guess it's all houses but... if anyone has any revolutionary tip I would be forever grateful).

65% is enough to grow mold? I read that more than 60% is enough to cause allergies. But mould I find it very unlikely. I feel like this house I live in is one of the driest I've been in (counting family, friends and all that).

The only problem is the air leakage through the wooden windows That doesn't help to maintain the humidity levels.
[/quote]

No. 65% isn't enough to grow mold, but if it's 65% in your (presumably heated) room, it's probably higher in the basement somewhere, or it's higher than 65% on wetter days, etc.

As for dust, consider a central HEPA filter. My wife has horrible allergies, and we attached one to our furnace. It draws something like 40% of the return air through the filter, and removes 99.9% of dust from it. The circulating amount of dust has cratered, and it's much easier to keep up with dusting/vacuuming because it accumulates so much slower.

[Drill]

If, in fact, your indoor RH is 65% in winter, there's a chance your indoor allergies are due to mold, not dry sinuses. If you have a basement, check the RH there. My parents had an old house that was usually 40-50% RH upstairs, but 80-100% RH in the basement, which doesn't discourage mold growth, let me tell you that. Also, people spend more time indoors during winter and dust might be triggering the indoor allergy.

Yeah, dust sucks and my house seems to have an infinite ammount of it (Guess it's all houses but... if anyone has any revolutionary tip I would be forever grateful).

65% is enough to grow mold? I read that more than 60% is enough to cause allergies. But mould I find it very unlikely. I feel like this house I live in is one of the driest I've been in (counting family, friends and all that).

The only problem is the air leakage through the wooden windows That doesn't help to maintain the humidity levels.

No. 65% isn't enough to grow mold, but if it's 65% in your (presumably heated) room, it's probably higher in the basement somewhere, or it's higher than 65% on wetter days, etc.

As for dust, consider a central HEPA filter. My wife has horrible allergies, and we attached one to our furnace. It draws something like 40% of the return air through the filter, and removes 99.9% of dust from it. The circulating amount of dust has cratered, and it's much easier to keep up with dusting/vacuuming because it accumulates so much slower.
[/quote]

Just a small observation (please don't take this the wrong way, I'm really thankful for all the advice):
One thing I've noticed both in your and in @beninma responses is that you are seeing the problems adapted to your climate/cultural behaviour eheh
Here in southern europe I believe we have more problem with our houses being humid than being dry because it never gets really that dry here.
We also never have really well sealed houses because the construction sucks.
And when you talk about heated houses, I say heated what? That's a thing for the rich only here Because we have sun 80% of the year we have to suffer from cold inside our houses the only 2 months/year that happens

My cousin went to Berlin (a lot of negative temperatures) and says that he suffered more from cold here than there (because the houses have a central heating system, otherwise they would die). Here because it never get's below 0, and it's usually more than 10º, no one cares...

[marqueemoon]

I just store my acoustics in their cases, tune the vintage ones down when not actively using them, don’t leave them in extreme heat or cold any more than absolutely necessary and let them acclimate in the case when changing environments.

I live in Seattle though. It isn’t the desert here… yet.