Annual Humidity post - SUPER IMPORTANT - READ THIS!!!!!!! (long, but worth it)
So, it's that time again. The time when I berate you all to humidify your guitars during heating season.
The specific requirements for humidity in your region will vary depending on your climate, but I live in the absolute worst part of the country for humidity, where it will go up and down about 60-80% over the course of the year, from low to mid 80% in the summer to as low as 5% indoors during the winter. These huge swings are killers for guitars, and in our shop we frequently see as many as 600 guitars over the course of the winter with humidity related problems (it gets a little busy!). So do what you can to take care of it.
Up here where I live, we never get so humid that you need to worry about your guitar getting too much humidity, though if you live in a swampy area you might have that problem. The problem here is low humidity. Guitars like to live in 40-50% relative humidity.
Houses being heated to 72 degrees Fahrenheit when the temperature outside is in the 10 degree range can easily get down to about 5%, and when it is 35 below I've seen it go as low as 2-3%. This is a particular problem on acoustic guitars, which are usually unfinished on the inside, so they will lose moisture to the surrounding air, which will cause the wood to shrink. This leads to all kinds of problems, from the top sinking (which pulls down the bridge, which pulls down the action and causes buzzing - some guitars come in and you can see from across the room that the tops look like salad bowls), to the wood cracking. Now, all of these things can be repaired, of course, but it is much better to avoid them if you can.
Electrics have fewer problems, but one thing which can be a problem for both acoustic and electric guitars is the fingerboard shrinking. When this happens, the frets do NOT shrink. On an unbound fingerboard, this is relatively minor, with the fret ends sticking out and acting like a serrated knife when you move up and down the fingerboard. It is painful and problematic, but it's pretty cheap to have fixed (we usually charge about $30 for it); but on a bound fingerboard, as the frets push out from the wood, they can cause the binding to come unglued, which can lead to all kinds of problems, and which is much more time consuming (i.e., expensive) to fix. And unfortunately, while a sinking top will usually come back with adequate humidification, fingerboards are too thick, and will never come all the way back.
So, what can you do about it? Glad you asked.
First, from the moment you turn on your furnace (or whatever kind of heat you use - even steam heat, which somewhat counter-intuitively is one of the worst for causing low humidity), you MUST be humidifying your guitars. I usually recommend that my customers put a little post it note on the furnace or by the thermostat reminding them to humidify their guitars. In my part of the world, I've got no real problem with people keeping up the humidifiers year round if that is what it takes for them to keep it up during the winter, as in the 35+ years we've been in business the only guitars we've seen which had been over humidified had spent a week or two in flooded basements.
There are several options for this, and some people like to just humidify the room they keep their guitars in, but this has some major problems. First of all, if you live in a wood house with windows, you will have a very hard time keeping the room up where your guitars want to be, 40-45% relative humidity. When it's really cold out, at about 35% the moisture just starts to condense out on the windows and you don't get any higher without putting massive amounts of water into the air. But even that has problems, because it is not just your windows the moisture is weeping out on (though, considering the mold and mildew this will cause, it's a serious enough problem), but also the studs in your walls. It will condense out and freeze on your stud walls, and you can literally rot your house from the inside out. If you are in a masonry or concrete building, you can get aways with it, but it is still problematic (because of the work we do, we MUST keep our concrete block shop at 45-50% year round, and we get some pretty serious mildew stains on some of the walls because of this).
So, what do you do if you want to keep both your house and your guitars in good shape in a cold environment? First and foremost, keep your guitars in their cases whenever you are not playing them. This is a pain (it's much easier to play a guitar that is sitting on a stand and all that), but if you want to keep your guitars in good shape it is essential, partially because it means that you have a much smaller space to humidify, but also because it will protect your guitar from knocks, bumps, and little curious hands who want to try daddy's (or mommy's) guitar. I've said it before, and I'll say it again, but ALWAYS KEEP YOUR GUITAR IN IT'S CASE, as it is never safer than when it is in it's case.
In order to maintain the guitar's humidification, I recommend a two humidifier solution. First, get a KYSER LIFEGUARD. They are, hands down, the absolute best investment you can make in maintaining your guitar in a dry climate. They are infinitely better than any other guitar humidifier on the market, and I'm not just saying that because I know the inventor (he sold the idea to Kyser about 15 years ago, and doesn't get shit from them anymore). They lock the humidity into the body of the guitar, where (because it is unfinished on most guitars) it is most vulnerable to low-humidity conditions. Other humidifiers are either too small, too difficult to fill, or they have hard plastic cases which can damage your guitar. The only tricks with the Lifeguard are that you must throw out the harder black packaging ring they come with (he actually intended it for guitars with very thin tops, but I've never see a guitar which need one), and you must be very careful to get all of the water out of the various crevasses on the outside of the humidifier. I fill it under a running tap (there is absolutely NO need to use filtered water, and anyone who says otherwise is just silly) until it is wet, but not dripping when squeezed, then I dry off the exterior with a paper towel (being very careful to get under the lip that holds it in the guitar), and put it in the soundhole. You can even play with them in, which can be handy if your SO is sleeping in the next room. They come in two sizes, one which will fit most round holed steel stringed guitars (model KLHA), and one for guitars with smaller soundholes (usually classical guitars or Martin O or OO sized guitars - model KLHC).
Second, go to Target and get yourself a covered plastic travel soap dish and a sponge. Drill some holes in the soap dish cover, put the (now damp) sponge in the soap dish, and put the whole thing in the case with your guitar. They usually fit quite nicely up by the peghead. You can also put a rubber band or old tee-shirt around it to keep it from falling open, and I had one customer put some Velcro in their case to hold it in place.
Check these humidifiers every time you play, but at least every 3-4 days in really cold weather (a bit less in warmer weather, but your playing your guitars every day, right? So checking their humidifiers will be no problem, right?). When they stop feeling damp, refill them. DO NOT FORGET TO REFILL THEM! If you do, don't complain to me when you have to pay $150 or more to get your guitar fixed. You've been warned.
If you live in a milder environment, you might not need to be so aggressive about this, but the flat truth is that unless you live in a swamp or use it as a canoe paddle, you will never get your guitar so over-humidified as to cause problems. It might sound a bit dull, but you will not cause damage to the guitar.
Always check with your local repair shop to determine the appropriate steps to keep your guitar safe in YOUR climate, but if you need to turn your heat on for more than a day or two at a time, you need to be humidifying your guitar.
With any luck, Muttley will chime in with what he recommends for people in cool damp climates like the British Isles.
Sorry this is so long, but it's important, and there is a lot of information you need to know if you want to maintain your guitar properly.
"Cowards can never be moral."
"It's not about who killed my son, it's about what's killing our children."