Humidifiers

John418

Can anyone recommend a good soundhole humidifier? I keep my guitar out of its case. Would a soundhole humidifier do the job or will I need to humidify the room? Guitar sounds like crap in really dry weather.

Bob Holo

Without a case to create an ambient environment of stable humidity, you're not really going to accomplish much with a soundhole humidifier. If you want to be able to see the guitar, there are wall-mount cases such as this:

http://www.acousticremedycases.com/prod ... climastand

But it really doesn't need to be high-brow. If you have an old armoire or a hall-closet - hang the guitar in it and put a pan of water on the floor - or if you're afraid the water will spill, put an old cookie-sheet on the floor - lay a diaper on it and pour water on the diaper and tack a cheap humidity gauge to the wall. The sodium polyacrylate crystals in diapers are the exact same thing most high-end humidors use. What you need is an environment that is humid because the guitar gains and loses humidity from every surface - internal and external as no finish is completely water-tight/gas-tight despite the long threads one can read on every chat board ever to hit the internet about how some finishes breathe and others don't. All finishes breathe a little, some synthetic ones breathe a little less, thick finishes breathe a lot less. The US Forest Service did some research back in the 40's on this. Granted, it was before the development of many cross-linked polymer finishes common today, but even shellac cross-links in the presence of common acids found in nature, so it's not like their research has become invalid. They found that the best way to create a water/vapor barrier was to put finish on a little thicker and maintain the surface to keep it free of cracks. Well, a good guitar finish runs between 2 to 4 mils... which is a fraction of the thickness of the finishes they were testing, so you can draw your own conclusions from this.

To give you some perspective on dehumidifying guitars and the importance of a humidified environment, Bob Taylor has a neat little cabinet that he uses to vary the humidity of guitars for various design and torture-test applications. It looks like a small commercial refrigerator and inside it there are a bunch of fans. He just puts the guitar in there and dials-in the humidity he wants and the ambient humidity of the chamber and air movement over the surface can take a guitar from bloated and dripping to mummified and sunken and cracked in about three days. Air movement is the real enemy because the surface of the guitar is a micro-climate. As the humidity in the microclimate is disturbed by the air movement, a differential is created where the surface is more humid than the surrounding air and the physics of evaporation kicks in creating a thin zone where the outer and surface humidities are averaged by pulling moisture from the more humid of the two. How fast this happens depends on the density and pressure differential of the thin layer of (relatively humid) vapor on the surface of the guitar and the kinetic energy (including wind) acting on the system. But suffice it to say, evaporation happens... same reason a hair dryer works.

About humidity gauges... Most cheapie dial gauges are crap - and I've never found a paper humidity test strip that passed the laugh test, but good inexpensive humidity gauges are easy to find if you look in the cigar enthusiast hangouts. This is darned near as good as the one I use in my shop and it's 24 bucks. In fact, over time I'll probably just transition to a bunch of these so I can measure different humidities in different places to make sure one assembly bench isn't 10% different than the other, for example. You don't need do know if the humidity is 50.1% or 50.3%... you just want to make sure it's not 30%. and these types of units work great and are typically accurate to within 5%. http://www.amazon.com/Digital-Thermomet ... B00153KVYG and for a few bucks more, you can find ones that you can calibrate - maybe this one can, I didn't check, I just googled: Amazon humidor humidity gauge or something like that. Bottom line, the mechanisms in these little buggers are very accurate, they just aren't stated as such because most people won't take the time to calibrate them every so often. But you can buy calibration kits for a few bucks and dial these things in to be as accurate as you could ever need for this purpose. Or if you're a chem geek, you can make your own calibration kits for a few cents. If you're at all in doubt, just buy a kit, as some of this stuff isn't necessarily good to touch, sniff or use in a mixed drink. http://www.robertharrison.org/icarus/wo ... peratures/

Bones

Also, it is best if the closet has no walls that are connected to the exterior of the building since there can be a lot of variation in temperature if your place isn't well insulated. I.e. if the back wall of the closet is also an exterior wall on the house that faces the sun.

I have case humidifiers (rags in small plastic bags with the openings loose) but I also have large yogurt containers with wet rags in them in the bottom of the closet if we get a particularly dry weather pattern since I live in a VERY arid climate.

PS- also be careful not to over humidify...