Humidity Matters

Over the years some reasonably good acoustic guitars have been made from a variety of materials, some natural and some synthetic.  Technology has enabled the production of laminates of better quality, and some manufacturers have even made  use of things like fiberglass and carbon fiber.  That being said, there is little doubt that the most knowledgeable and  demanding players chose instruments built with all solid timbers;  no laminates, no epoxy, no digitally produced pictures of high-grade woods.  Just genuine, select tonewood.

That is why Timberline guitars are built with solid woods, all carefully chosen for specific functions within the overall package.  Spruce, mahogany, various types of rosewood, ebonies and other species are gathered from all around the world, carefully split and sawn to ensure perfect grain orientation.  These timbers are methodically dried and stabilized, then worked by hand and machine to create the best instruments we know how to build.

When a player is ready to make the step up to an all-solid wood guitar he or she needs to understand how to care for that instrument to ensure that it will continue to age and develop it's full voice without coming to any harm.  The maintenance of such instruments is not complicated, costly or difficult, but a little bit of care will ensure that your investment is protected and that your instrument may be a lifetime companion.

The beauty of wood is that it is a completely natural material.  While the tree which gave us the gift of a beautiful board may be cut down, the wood itself continues to respond to atmospheric conditions as if it were still alive.  If a piece of wood is moved from an environment which is very dry to one which is very wet, the cells of the wood absorb airborne moisture over a period of roughly 3 days until they have adapted to the new environment.  Since the wood is taking on new moisture, the board actually expands somewhat in size.  This growth is noticeably greater across the width of a board than it is end to end.   On the other hand, if that wood is then removed from the moist environment and put into a very dry room, it will give up the moisture to the atmosphere over roughly 3 days and will noticeably shrink in width.

The best guitars are built in controlled environments, calculated to protect the finished instruments from extremes of climate to the greatest extent possible, but those controls have limits.  Because the expansion and contraction of various species varies from one to another under the same atmospheric conditions, guitar tops tend to grow and shrink to a greater extent than the hardwood backs and sides.

As a general rule a good instrument should be kept ( if possible) at a relative humidity level between about 35% and 50%.  Relative humidity is measured with an instrument called a hygrometer, and every guitarist should own one.  They are available at electronics shops and even some drugstores, priced from about $20 up.  Hygrometers measure the amount of moisture in the air, and express it as a percentage of the amount of moisture that it would be possible for the air to hold at any given temperature, so a reading of 50% relative humidity means that the air in that room has roughly half the amount of moisture that it can hold before it starts to release it in the form of fog or rain.  Obviously it doesn't very often rain indoors, but if you take your hygrometer into the bathroom while you're having a shower, you'll see a reading of perhaps 90% registered when you steam the place up.

High relative humidity readings are much less harmful to guitars, pianos, fine furniture etc. than are low readings.  An excess of airborne moisture generally just expands the wood enough to cause the top to rise a little bit, perhaps raising action, but it will very rarely cause permanent harm.  Very dry readings on the other hand can cause permanent damage.

If the humidity in the area where you keep a fine instrument drops below about 35% you may notice strings starting to buzz on frets.  That is because the normally slightly arched top gives up enough moisture to shrink slightly across its width, lowering the bridge and action.  If the level continues to fall to say 30% a close examination of the top may show a slight 'corduroy' effect.  You may be able to see and to feel slight ridges as you run your fingers across the top.  These are caused by the difference in nature between the darker 'grain' lines and the wider, lighter colored 'summer growth' in between the harder lines.  Actually those lines running vertically down the top are not 'grain' at all, although they have been called that mistakenly for years.  They are in fact the annular growth rings of the tree, showing up as straight lines because a good top is always quarter-sawn.  An excellent explanation of quarter-sawing timbers can be found in Bruce Hoadleys' book ' Understanding Wood', which we highly recommend to anyone curious about the topic.

The dark lines are thinner, harder and more dense than the wider 'summer growth', so the wider material gives up moisture faster, shrinking slightly in between the harder lines to cause the appearance and feel of corduroy.  If your guitar starts to exhibit that effect, it's time to get some moisture into the atmosphere.  This can be done easily and economically by use of a wide range of humidifiers from cheap drugstore vaporizers to complex automatic units.  The secret to good humidity control is to own and use a hygrometer, so you never have to guess about moisture content in the air.

     If you allow the humidity to continue to fall, at about 25% you may be able to feel fret ends sticking out of the sides of the fingerboard as the fingerboard shrinks across it's width.  Under 25% you can expect to start seeing cracks develop, usually showing up first in the top next to the fingerboard, in the board itself, and/or in the bridge.  Of course that is to be avoided, even though such damage may be able to be repaired.

In areas of the country with wide ranges of temperature from season to season, instrument owners need to be aware of humidity fluctuations to a greater extent than those living in areas with little difference between seasons.  In places where winters bring very cold temps.,  various forms of heating dry interior air out quite quickly and positive steps must be taken to ensure stable humidity levels for your instruments.  Incidentally, very low humidity is not good for humans either, not just instruments.  At low humidity levels many people find they are prone to nosebleeds, dry flaking skin, etc., and fine furniture tends to loosen its joints and generally misbehave.

All the above notwithstanding, all you really need to know is the following:

  • Buy a reasonably good dial or digital hygrometer.  Put it near to where you keep you instruments, and CHECK IT DAILY.  If the relative humidity starts to drop below 40% take steps to introduce moisture into the air until the level rises to about 45%.  If the room is small, that's easy to do with a very cheap vaporizer from the local drugstore.  If the room is larger you may want to invest in a larger drum type humidifier, ranging from around $100 to $250 or so.  All these devices need human supervision, which means you must check them every 10 to 24 hours and make sure they have a good supply of water in them.
  • Houses with furnaces or other means of central heating usually have a central humidifier on that device.  Many of those are fed automatically from the waterlines, and all are adjustable so you can determine the humidity level best for your instruments, furniture, pets and yourself.  Do not leave your guitar next to a fireplace, heat radiator or heat vent.
  • There are a number of small humidifying devices which are meant to fit inside the soundhole of the guitar, or inside the case.  Those may help, but only if you check them on a very regular basis and make sure they are filled as required.  Stop using them as soon as the humidity stabilizes at 40 to 45%.  They are better than nothing, but are not as reliable as room humidification.

If you follow the simple rules of humidification you will protect your guitar, ensure it always plays as well as it should, and you will probably reap the benefits of higher resale values when it comes time for you to move up to an even better model in the Timberline family of fine guitars.

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