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Thread: Annual Humidity post - SUPER IMPORTANT - READ THIS!!!!!!! (long, but worth it)

  1. #11
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    Quote Originally Posted by muttley600 View Post
    In this countries climate a barometer will tell you a lot about the atmosheric water content. Next to no average person would know where to get or how to calibrate a hydrometre. A decent hydrometre that gives reliable results will often cost more than the guitar itself. A barometre will tell you the change in atmospheric pressure and in nearly all cases it is a related to the vapor in the air. What you want to measure is the swift change in the prevailing conditions not the exact amount of moisture. At a cost of £5 for a decent barometre against £200 for an average quality hydrometre you can get all the information you need to identify that the degree of change in air vapor is great and get a good idea of the impact seasonal changes have. We arn't really interested in meteorological accuracy of the results just that the moisture in the air changes swiftly and to a significant degree.
    Then I guess I really don't get it. Didn't you advise using a barometer to measure the difference between indoors and outdoors? I don't see how barometric pressure can be different between the two. Humidity, yes. And as Light says, when you heat the air in your home, you decrease the relative humidity in that air, and the barometric pressure has not changed.

    And here's one for less than a hundred bucks:
    http://www.reliabilitydirectstore.co...FQ83gQod8jAUsA

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    Quote Originally Posted by ggunn View Post
    Then I guess I really don't get it. Didn't you advise using a barometer to measure the difference between indoors and outdoors? I don't see how barometric pressure can be different between the two. Humidity, yes. And as Light says, when you heat the air in your home, you decrease the relative humidity in that air, and the barometric pressure has not changed.

    And here's one for less than a hundred bucks:
    http://www.reliabilitydirectstore.co...FQ83gQod8jAUsA
    A barometer will give you an indication of the absolute humidity of a column of air and its relation to the weight of that column of air. Atmospheric pressure is related to the amount of water within a given column of air. A hydrometer will give you an indication of specific humidity at the place at which it is measured. I have not suggested that a barometer will measure humidity for you. I have always said it will give you an indication of the manner in which humidity and vapor pressure change in relation to seasonal changes, specifically in the British Isles. This it will do. Taking measurement both inside and out over a period of time also give an indication of the importance of temperatures and vapor pressure in the relationship. The key here is using a barometer to demonstrate that the temperature and vapor in the air will change swiftly and mean values for summer months are different from winter months. Not that the moisture is actually there in the first place. You don't need an expensive hydrometer to do this. By all means use one if you need the data to be that accurate.

    In one sense your guitar is a barometer in that it will react reliably to the same phenomena that the barometer is measuring.

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    Quote Originally Posted by Oancient1 View Post
    Good post Light.

    I don't worry about humidity now as my guitars always reside in a room in my Virginia home that I am able to keep the level relatively constant in a good range. However, within a year or two we plan to move to Tucson AZ, where I am sure that lack of humidity will be a real problem. So thanks philboyd studge for the commentary from the desert. It's to know that desert conditions can be dealt with. (Where are you at by the way?).

    Please correct me if I am wrong, but common sense tells me I should be less worried about my electric than the acoustics. One of the latter is a cheapy import left over from my son's short lived interest in learning to play guitar. But the other is a rarely played vintage Martin 12-20 12-string that is currently in very good condition I hope to find an interested buyer locally and sell it before moving, just sos I don't have to worry about it. Otherwise, I guess the LIFEGUARD thingy combined with the damp sponge would seem to be perfect for keeping it in good shape.

    Thanks again to the info guys.

    Tom
    I'm on the East side of the Coachella Valley. Since humidity is often in the teens here, it's pretty low in the house after the heat pump gets done heating or cooling the air and that presents another set of problems; that's the natural enviornment here so if you're taking your guitar out its humidfied case you're exposing it to extreme change, whadda ya do? Basically not much, just keep instrument out no longer than it has to be, up to 4 hours or so, and if there's no huge in temperature you should get through things ok. Some folks here don't do anything to humdify and reset setup and action for the lowered top but you're asked for eventual finish checking, possible cracks and loose braces.

    I had a D12-20 for quite awhile but sold it about ten years back....at a time I was doing little to humidify my acoustic guitars. Only the J-200 as I recall. Anyway, the Martin held up well and had no finish or neck issues and was a testimony to the most important thing you can do....keep it in its case and away from extreme changes. Though it would have been better to humidify it somewhat I got by and was lucky.

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    Quote Originally Posted by Zaphod B View Post
    So, keeping things really simple for a simpleton such as me - an in-case humidifier consisting of a damp sponge in a drilled travel soap container will give me all I need for my electrics? Why didn't anyone tell me this years ago?

    Yup, pretty much.

    As for the hygrometer issue, we have a really nice one in the shop, and it typically reads within 4-5% of the cheap ass digital ones we have up throughout the shop. The cheap ones will not give you a perfect reading, but they will give you a close approximation, which is all you really need. If you see a big change in them, then you know you need to take some action.

    We have an old super nice hygrometer with a good humming bird wing diaphragm (yes, they are really made of humming bird wings) that we almost never look at other than to double check on the cheap ones. Really, though, it's not that important that you know exactly what it is unless you are trying to humidify a room. Otherwise, just start humidifying as soon as you turn on your heat, and you'll be fine. Though air conditioners (cooling) DOES lower the humidity, we have never seen a single guitar that was cracked from it. All the ones we see in the summer are of the "Yeah, it cracked last winter, and I just didn't get in until now," variety (with all the dirt and grime in the cracks which goes with it), and never of the, "this crack just showed up," sort.

    As far as cold, though it is certainly possible for it to cause wood expansion, I've never seen structural damage from cold (and we get bloody cold up here). The cold issue we DO get a lot of is weather checking, which is from a cold guitar suddenly getting too warm. The wood expands faster than the finish, and you get many fine cracks in the lacquer. This one happens all the time, and there isn't really much you can do to repair it. Their are several ways to avoid it, starting with the builder using a vinyl sealer instead of a straight sanding sealer (it's more flexible), but the main thing for the player to do when their guitar gets too cold (left in a case in the trunk on a cold day, for instance) is to leave it in the case until it has come to room temperature. When customers ship us guitars, we will leave them in the box for at least a day. The point is to slow down the speed of the temperature change so that the process happens more gradually and the lacquer never gets too stressed.

    But again, weather checking is really only a cosmetic problem (though it can effect collectible value, so be careful with those old Strats and D-28s), so I don't worry TOO much about it with my own guitars. With a customer's guitar, I'm fanatical about it, of course, but I don't mind playing a guitar that looks lived in, personally. Humidity issues are serious structural issues, so I worry a LOT about those.


    Light

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    Quote Originally Posted by muttley600 View Post
    A barometer will give you an indication of the absolute humidity of a column of air and its relation to the weight of that column of air. Atmospheric pressure is related to the amount of water within a given column of air.
    I'm sorry, but I don't see how that could be true. Humidity is not a constant top (meaning to the top of the atmosphere) to bottom in the column of air; it's a local phenomenon, especially if you are in a building where it can be quite different from what it is outside. Absolute humidity doesn't determine the drying ability of air, either; relative humidity does, which is exactly what Light was saying. When you heat air which is at 10 degrees F to 75 degrees F, its absolute humidity does not change, but the relative humidity will drop from (possibly) 100% to very much less than that, putting your acoustic instruments at risk.

    And are you saying that a barometer will register a change if you go outside a building that has a different relative humidity than ambient, even if it is not sealed? I can't see how that could be true; the pressure would equalize whenever you opened a door even if it were sealed. Furthermore, while it is true that wet air weighs more per unit volume than dry air, days of high barometric pressure are frequently (usually, even) dry. That would seem to run counter to your claim.

    Can you point me to a scientific discussion somewhere that can describe the details of what you assert? It does not seem reasonable to me.
    Last edited by ggunn; 10-31-2007 at 13:16.

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    Quote Originally Posted by ggunn View Post
    I'm sorry, but I don't see how that could be true. Humidity is not a constant top (meaning to the top of the atmosphere) to bottom in the column of air; it's a local phenomenon, especially if you are in a building where it can be quite different from what it is outside. Absolute humidity doesn't determine the drying ability of air, either; relative humidity does, which is exactly what Light was saying. When you heat air which is at 10 degrees F to 75 degrees F, its absolute humidity does not change, but the relative humidity will drop from (possibly) 100% to very much less than that, putting your acoustic instruments at risk.

    And are you saying that a barometer will register a change if you go outside a building that has a different relative humidity than ambient, even if it is not sealed? I can't see how that could be true; the pressure would equalize whenever you opened a door even if it were sealed. Furthermore, while it is true that wet air weighs more than dry air, days of high barometric pressure are frequently (usually, even) dry. That would seem to run counter to your claim.

    Can you point me to a scientific discussion somewhere that can describe the details of what you assert? It does not seem reasonable to me.
    I'll say again

    I have not suggested that a barometer will measure humidity for you. I have always said it will give you an indication of the manner in which humidity and vapor pressure change in relation to seasonal changes, specifically in the British Isles.
    Take a balloon and inflate it add say 2 grams of water. Measure how it behaves in relation to change in temp and (altitude). Do the same with dry air. Next burst the balloon and measure the same air in relation to it's pressure and specific humidity.

    I never said that a barometer will give you an accurate measure of humidity. I have said that here you can more than reliably predict changes in humidity with one. People have done so for years and will continue to do so. More importantly I described it as a method of understanding how swift changes in humidity and temperature can take place in relation to seasonal changes and the meteorological phenomena that result. Here in the UK I can predict the humidity quite accurately just by observing which way barometric pressure is moving.

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    Quote Originally Posted by muttley600 View Post
    I'll say again



    Take a balloon and inflate it add say 2 grams of water. Measure how it behaves in relation to change in temp and (altitude). Do the same with dry air. Next burst the balloon and measure the same air in relation to it's pressure and specific humidity.
    To prove what, specifically?

    Quote Originally Posted by muttley600 View Post
    I never said that a barometer will give you an accurate measure of humidity. I have said that here you can more than reliably predict changes in humidity with one. People have done so for years and will continue to do so. More importantly I described it as a method of understanding how swift changes in humidity and temperature can take place in relation to seasonal changes and the meteorological phenomena that result. Here in the UK I can predict the humidity quite accurately just by observing which way barometric pressure is moving.
    Oh. OK, so you can watch a barometer and tell when a storm is coming. All right, but what was throwing me off the track was this passage:

    "A lot will depend on what, where and how your store your guitars. Do you take em out lots? How long for? What guitars? Where you are in relation to the coast? Get a barometre and take a look at the difference inside and out over a period of time."

    Inside and out of what? I read it as looking at the difference in barometric pressure between indoors and outdoors, and that doesn't make sense, obviously.

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    The point being that you can use a simple tool to help you understand how the prevailing climate in your areas changes and changes swiftly. You don't need to know what the humidity is just that it changes in relation to the season and quickly. This is the danger your guitar faces. A guitar will handle quite high relative humidity and also quite low humidity. It will not appreciate being thrust from one to the other in a short space of time. If the change is gradual it will cope much better. Thats not saying it's a good idea though. Maintaining a controlled environment is by far the better way to go.

    If I rephrased the comment you just quoted I'd make that more clear.

    If you were to move your barometer outside to a cold wet climate from indoors in a dry heated environment, temperature would be the biggest factor in any change in the reading you get. Vapor pressure would be secound. Yes, that would indicate a need to recalibrate rather than a specific change in the atmospheric pressure.

    Really I wish I'd just said check the detailed weather forecast frequently and examine how high an d low pressure are related to humidity in temperate climates rather than look at a barometer it would give you the same information just less graphically.

    And yes if you want to know the actual relative humidity of a specific location a hydrometer is the best tool. I have several in the workshop. None are perfect. I always look to keep the changes gradual in any case as the extremes here are not that great.

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    If people were really that concerned with protecting their instruments from a change in humidity, they would never leave their house.

    I guess the old timers never played a live gig or left their houses without a hygrometer.

    Much ado about nothing. Hell, I spray water inside my acoustics with a garden hose.

    Of course, I use the fine spray attachment.
    [SIGPIC][/SIGPIC]Instant Karma tried to get me... and succeeded

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    dang, all I use is a thermometer with two sides, one reads temp fareinheit and the other reads percent humidity...it cost me $5...
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