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IMPORTANCE OF HUMIDITY CONTROL
The following information was compiled by STONEMAN GUITARS from various sources. This is
VERY IMPORTANT information on humidity and it's effects on Guitars and
stringed instruments in general. This following information is essential
reading for instrument owners, and a MUST READ for musical instrument
dealers.
A
Call for the Standardization of Humidity Levels at
Musical Instrument Dealerships
All
U. S. manufactures of electric and acoustic guitars follow basically the same
procedure for the drying, and conditioning of the wood used in their
guitars. It is imperative that the
retailers who represent our products provide the proper temperature and
humidity conditions so that their guitars are maintained in excellent condition
for the duration of the selling process
Each
of the undersigned manufacturers builds guitars to high quality standards and
has invested heavily in factory equipment and systems to insure that these
standards are consistently delivered to our customers. We also spend large sums of money on
advertising campaigns to bring guitar players into the retail stores to view
our instruments. These guitars are made
of wood, and thus are affected by changes in temperature and humidity. When our products are shown to potential
customers in a situation where failure to maintain proper climate conditions has
adversely affected the guitar, they are not being shown as we intended. As a result many customers might make
negative judgments about our products when, in fact. it
was the retailer's humidity conditions that caused our guitars to be in less
than desirable condition.
Retailers
will also benefit from this standardization. They will find that their sales, profits,
and satisfied customers will continue uninterrupted through the cold and dry
winter months. Retailers
know that throughout the late
spring, summer, and early fall months,. the climate is acceptable and there is little need for sending
guitars back to manufacturer. In the winter however, many retailers need to return guitars to the
manufacturers for service or perform the service in their own repair
departments. These costly repairs can be
avoided through humidification. This will
benefit our entire industry,
including the retail customer, the dealer, and the manufacturer.
We
are calling our retailers to:
1.
Maintain humidity levels at about 50%
in both their sales and storage areas.
2. Maintain
temperatures, even at night, no lower than 60
degrees.
3. Have accurate humidity gauges to monitor
humidity levels.
4. Have the reserve capacity to handle the
unusual conditions that cause extra low humidity.
Our goal is to have dealers of our products
install the necessary equipment by the November 1994.Signed by:
Taylor Guitars, Gibson Guitars, Guild Guitars,
Martin
Guitars, Ovation Guitars, Fender Guitars and others.
It turned out that the above signed companies were just
TRYING to demand this of their dealers and ALL have "backed down" on
enforcement of these VERY IMPORTANT guidelines. (At the time of this writing). STONEMAN GUITARS
is, and always be, a total temperature, and humidity controlled shop.
An alternative layout may be used,
by building an acoustic guitar room. Smaller humidifying equipment could then be utilized, however, the room must have an automatic
door closer, and cannot exchange air with the main building via the
heating, and air conditioning system.
Considering the relatively low cost of humidifiers, a separate acoustic
room can sometimes become more costly than humidifying the whole store.
Note: The acoustic guitar room must not share the
ventilation with the main building and must use an automatic
closing door (glass).
A thorough understanding of humidity and how it affects
guitars is becoming more essential to the guitar store owner. Many producers of high quality, solid wood
guitars are requiring their dealers to maintain a safe level of humidity in
their stores, and dealers themselves are discovering that their stock of
high-end acoustic guitars is at risk when their store's humidity becomes
excessively low or high. The information
in this guide is provided to you as a dealer of fine instruments so that you
can gain an understanding of how to control the humidity in your store. We have taught many dealers the secrets to
controlling humidity, and, once implemented, they have experienced higher sales
volume due to the tact that their guitars are in such wonderful condition.
There are many reasons to control the humidity in your
store.
Most factories control their climate and most guitar owners
keep their guitars protected in cases.
Thus, the retail store has the potential to be the worst environment
that a guitar will experience. Being on
display in a retail store exposes the guitar to the store's environment, and
the guitar will react accordingly. By controlling tire humidity you can give
your 6ustoiner a product that is in the best possible condition, the same
condition as when tire manufacturer sent it out from his facility.
Controlled humidity will benefit all of your guitar stock,
not just solid wood acoustics. You will
have fewer sharp fret ends poking out of the sides of shrinking fingerboards on
electrics, as well as acoustics.
Although we understand that plywood 2uiturs probably will not crack due
to extreme dryness, their tops and backs will still shrink, thus affecting
their action and overall feel.
Retailers who control their humidity experience a dramatic
decrease in the need to return guitars to manufacturers. This is good for the manufacturer, and the retailer
does not have his business interrupted and his money tied up while guitars are
being returned. Most manufacturers are
becoming strict about what they will or will not take responsibility for, and
are able to detect the effects of exposure to extreme humidity, especially low
humidity.
Wood is not replaceable!
This is a different day and age than we've seen in the past, where
guitar woods were plentiful and inexpensive.
As manufacturers, we are increasingly grilled by our customers us to
where our wood came from and what we are doing to conserve that wood. Yet, every year, we see many guitars that are
damaged due to a lack of attention and concern over the one thing that can
utterly destroy a good guitar.
Humidity control is an action to be proud of, and can be
bragged about in your promotion. Most
good salesmen will understand that their store now has another competitive edge
and will make a big deal of it to their customers. Soon they are teaching customers about
humidity and have once again become an opinion leader, an expert, proven by the
condition of the guitars they have in stock.. People love
to buy from experts.
Humidification is very cost-effective. It is not very expensive to install steam
humidifiers that have the capacity to control entire music stores. This is much easier than building separate
acoustic rooms that need to be maintained by your salesmen. If you want an acoustic room for sound and
display reasons, its humidity can easily be controlled as part of the main building.
What is humidity?
Humidity is a state of moisture in the air, usually
invisible, but frequently evident in the form of dew, mist, fog, clouds, rain,
and snow, all of which represent moisture that was previously absorbed into the
air by evaporation.
Actually humidity is the actual amount of moisture present
per volume of air.
Relative humidity is the ratio between absolute humidity and
the quantity of moisture that the air could contain short of its condensing
into fog, rain, snow, etc.
We will concern ourselves mostly with relative humidity since
it has the greatest effect an guitars and is easiest
to control. Read the definitions of
actual und relative humidity again. if you'd like,
since they can be a bit confusing. I
will try to explain, through examples, what relative humidity is all about, but
first I want to explain condensation and evaporation.
Condensation is when the temperature of moist air falls to a
degree at which it can no longer hold the amount of water vapor it
contains. The excess water turns to
liquid, or condenses. When the ground
cools at night, dew, or frost is the form of condensation. Condensation taking place on the dust
particles in the air is fog; that taking place in the upper regions of the air
becomes a cloud; and when the condensation is great enough the drops fall as
train.
Evaporation is the conversion of liquid into vapor. It is produced by heat, supplied either
directly or from surrounding objects.
Water evaporated into the air is measured as humidity.
Warm
air can hold more moisture than cold air.
The reason tile word "relative" is used is because
the humidity is relative to the amount of moisture that that particular temperature
of air can hold before condensation begins. If the actual amount of moisture remains
constant the relative humidity will change when the air changes
temperature. If the temperature remains
constant, the
relative humidity changes by adding or subtracting moisture. Fifty percent relative humidity means that
the air is holding 50% of its capacity, at its current temperature, before
releasing the moisture through condensation. 100% relative humidity means that
the water will now condense out of the air.
The rule is, if you raise the temperature, then the relative
humidity drops, and if you lower the temperature the relative humidity will
rise.
If you close a room and then raise the temperature in that
room, the relative humidity will drop.
This is because warm air can hold more moisture than cold air and
humidity is measured relative to how much moisture tire air is able to
hold. So, if a 55 degree room has a
relative humidity of 50% and you beat the room to 75 degrees, then you have
increased its capacity to hold moisture, and the moisture present when you
started would now be 25% of what the air can now hold. Thus, a new relative
humidity of 25%. If 50% humidity
is required in this room, you must add moisture.
Have you ever heard the term "dew point" on the
weather report? The weather man might
say, "The dew point tonight is 56 degrees." This means that the
weather service has done their calculations and knows that when the air outside
cools to 56 degrees, then it will have reached 100% of it's
capacity to hold tile water vapor that is present, and dew will appear. It may be 75 degrees and 60% relative
humidity at the time of the report, but as tile air cools at the end of the day
it is able to hold less moisture, so the relative humidity rises. The actual amount of moisture didn't change,
only the temperature.
By now you should be understanding
this concept enough to explain why your iced tea glass gets beads of water all
over the outside. The cold glass is
actually cooling tire air around it to tile dew point. Now, how much air do you think can possibly
be effected?
Not much, but it is common for a rather large puddle of water to end up
on the table around your glass. Imagine wiping all that water over the inside
of your guitar. You wouldn't dare! It seems like too much, yet all this water
exchange has taken place around a single glass.
Think of the amounts of water that are given and taken through processes
like this in a normal store. Moisture is
being drawn from wood and absorbed by wood all day long,
you just can't see it because it is in the form of vapor. And not only does wood give and take
moisture, but your clothes, your body, the walls, tile carpet, all these things participate.
What should the retailer do?
At first glance, preventing damage is the major goal of
controlling humidity. But there are many
stages of change that a guitar goes through before it becomes damaged. Let's say a guitar was dried out enough to
crack. It only makes sense that the
guitar did not go from perfect to cracked in one
motion. What actually happened is that
the guitar slowly dried, the wood slowly, shrunk, the
top slowly, caved in until there was no other way of relieving the stress, and
then the wood cracked. In between the
normal stage and the cracked stage, the Lop slowly lowered, bringing the strings
along with it. Please read my technical sheet
"Symptoms of a Dry Guitar" to see exactly what happens to a guitar as
it becomes dry.
Guitars that are exposed to too much humidity go through a
similar change, only they are swelling instead of shrinking. Soon, they, too, reach their limit and scams
separate, bridges come loose, action is unbearable, ect. Please
read "Symptoms of a Wet Guitar" to learn the details of this scenario.
The point is that guitars display symptoms of improper
moisture content, and these can be detected at a glance one only educates
himself a bit. Just because a guitar is
not cracked, doesn't mean that it is in good condition. Many retail stores sell guitars that are actually
right on the verge of cracking be4ause their store is so dry. The store owner doesn't even know he's doing
this disservice to the customer. If you
want guitars in your store that ;ire in top playing
condition you can actually adjust them all at the same time by controlling,
your humidity.
An expensive guitar should be delivered to a consumer by a
retailer who controls his humidity, thus enables the consumer to buy a guitar
that is in the condition that the manufacturer intended. A new guitar should be exactly that .... a new guitar! Then, along
with the manufacturer, the retailer needs to teach the customer how to protect his guitar
from extremes in humidity. Then, and only
then, will the cycle of the maker, the seller, and the buyer become harmonious.
If humidity control is so important, how have we gotten by
for so long without it?
We haven't gotten by, really. If you would spend a winter day in the customer
service office of any guitar manufacturer, listening to the incoming calls from
all over tire country about guitars that are damaged due to low humidity, you
would know for yourself that it is a bigger problem than you may have thought.
On the other hand, we have gotten by. But “getting by” isn't much to brag about. What about
taking our industry to its
potential? How about setting new
standards and moving on from there.
If you take the time to read and understand this information,
you could become a much more powerful dealer of fine guitars. Even if this is confusing and sketchy, you can
gain almost all of the benefits by doing one very simple task...... Humidifying your Store.
How does the relative humidity affect wood?
Every organic, porous substance tries to equalize to the
surrounding air, both in temperature and humidity. We tend to understand those things that we
feel the effects of and ignore those things that we don't, so I'll use
temperature as an example. If you stand
in cold air, you're going to get cold.
If your car sits in a hot, or cold garage, it
gradually becomes the same temperature.
Humidity works the same way. If
you put something in a dry atmosphere it too will become dry. Like dehydrated food, or towels in a dryer,
wood will equalize to the surrounding conditions. If the condition is dry, the wood will become
dry, if the condition is wet, the wood will become wet.
When wood takes on moist6re, it swells or grows. When wood gives up moisture, it shrinks. This is a physical characteristic and cannot
be argued to the contrary or prevented.
Maybe the most noticeable example of this, which you might have
encountered, is a door inside your house that sticks in the wet season and swings
freely in the dry season. Even with
paint on the door, to seal and protect it, the wood will shrink and swell with seasonal
changes
What is normal humidity?
40% to 60% relative humidity is considered normal. On an average, most locations hover around
this and most people are comfortable at this humidity level. Some areas, however, have a hi.-her or lower
average than this. Seattle has a high
average. Phoenix and Colorado have a low
average. Minnesota is high in the summer
and low in the winter.
The air inside your store originates from
outside. When you change the temperature
inside by heating or air conditioning you also change the relative humidity. This change may be good or bad depending upon
whether or not you stay in the 40% to 60% range. Humidity can be added with a humidifier and
subtracted with a dehumidifier. Air
conditioning units are, in effect, big dehumidifiers. In the summer, when it is humid outside, you
air-condition your store. You have been,
all along, without even realizing it, dehumidifying your store in the summer. That’s
good!
In some areas
additional dehumidification may be required and there are desiccant and refrigerant types available.
If the guitar woods are properly dried and aged, why does
the humidity need to be controlled?
Guitar woods must be properly dried before the construction
process begins. In our case, we dry wood to a much
lower moisture content than we ultimately build at to "ring out" the
last of the water that was originally present in the tree. We then condition the wood back up to a more normal moisture content. We have found that this process helps to make
the wood a bit more stable than if we just dry down to the proper moisture
content for building.
There is a term in woodworking called EMC. This stands for Equilibrium Moisture
Content. It means that at a -given
relative humidity, wood will equalize to a corresponding moisture content. As an example. at 45 % relative humidity wood will equalize to about 6% moisture
content. Generally, this is an accurate
rule, but it is affected by air flow across the wood ,
temperature, thickness of the wood, etc.
'Mere is a big difference between wood at 6% and wood at 7%; a 16 %
difference to be exact.
So, as guitar builders, we are faced with a decision
regarding the relative humidity at which we build our guitars. Most manufacturers choose about the same
humidity. Through years of experience,
we have all arrived at similar conclusions.
At Taylor, we build at 75 degrees and 47% relative humidity. We could choose 35%, and our guitars would
never crack due to dryness, but they would literally blow up and pop in higher humidity. We could choose 60% and the guitars would do
great in Hawaii, Seattle, the Midwest in the summer,
etc., but they would crack into pieces in die winter when it gets dry. The conditions that we create give the
guitars their absolute best chance for survival when exposed to extreme
conditions for a short period of time. They will, however, become damaged if they
are exposed to extremes.
Try this humidity calculator! You can usually get your daily
outside temperature and humidity, from the weather channel on TV,
www.weather.com , or your local
newspaper, as well as your own gauges.
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Possible Effects of Indoor Humidity |
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Less than 30%, TOO DRY |
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More than 60%, TOO WET |
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Damage to wood floors, furniture,
MUSICAL INSTRUMENTS |
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Termites, cockroaches, and other insects |
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Static electricity; electronic equipment damage |
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Condensation and stains on walls, ceilings, windows |
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Increased dust |
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Flaking paint and peeling wallpaper |
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Respiratory, throat, and skin irritations |
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Mold, mildew, dust mite growth; allergic reactions |
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Moisture content in wood and Relative Humidity in air.
Without exception, all woods are affected dimensionally by changes in the woods moisture content.
The woods moisture content is "varied", "regulated", or changed by the "relative humidity" in or of the surrounding atmosphere, and the ambient air temperature.
Relative Humidity is measured as a percentage of the air's capability to hold moisture. A 30% relative humidity reading means that the air is holding
30% of what it's capable of holding. The moisture content of wood is quite different. The woods moisture content, is how much water is in the wood. "Green wood" has a much higher water content or moisture content.
"Dry" wood, "Kiln dried" wood, and wood suitable for instrument building is much lower than is a "green" (living or freshly cut) tree.
Instrument construction requires a 6-8% "moisture content". "Raw" wood can either be "kiln dried" or "air dried" (for two years at least), to attain the 6-8% reading.
Now, to maintain the desired 6% moisture content the wood (instrument) should be kept at a 30% relative humidity (of the surrounding air) at 72 degrees F (22.2 degrees C).
The greatest damage to a musical instrument (wood) can come from changes in temperature and humidity.
High humidity can cause the softening of glues used, and the excessive "swelling" of the wood. Lowering the humidity, causes the wood to "shrink" and crack. You will experience the shrinking of the wood on a guitar or bass,
by feeling "overhanging frets".
Keep you guitar away from extremes in temperature or humidity. Also avoid slow sustained CHANGES in humidity.
do yourself and your instrument a favor. First purchase an accurate humidity gauge .... and use it! ......
Then make sure you use a good humidifier it the winter, and summer when your air conditioner is on!
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