Moisture Content and Humidity

Wood is a porous, organic material, and is affected dimensionally by changes in the amounts of moisture it contains. Fine guitars made from solid woods are without a doubt more susceptible to the effects of changes in humidity than laminated instruments, and therefore require ongoing attention to their condition.

The moisture content of wood is determined by the relative humidity and temperature of the surrounding atmosphere.

Relative humidity is expressed as a percentage of air’s capability to hold moisture. For example, 30% relative humidity means that the air is holding 30% of the moisture it could possibly hold at a given temperature.

The moisture content for wood and the relative humidity for air are measured quite differently. In wood, a 6% moisture content is present at 30% relative humidity and 72 degrees F temperature, (about 22.2 degrees celsius).

Protection from Temperature and Humidity

Indeed, the greatest natural threats to a fine wood guitar are extremes of and rapid changes in temperature and humidity. High humidity can soften the glues used in building an instrument, and can cause the top and back (especially on flat-top and classical guitars) to expand and rise—raising string action too high. Or, if you live in a drier, low-humidity climate (hot or cold) or travel with your guitar to one, evaporation of moisture from the wood can cause shrinking and cracking. This can happen no matter how old the wood is, and string action can become too low if the top and back shrink enough.

The ideal temperature for solid-wood acoustic guitars is in fact normal room temperature, which is about 70 degrees F (21.1 C). The ideal humidity is about 45% to 55%. In winter, the heating systems used in many homes can drive temperatures up and humidity levels dangerously low for guitars.

A good way to protect your guitar from drying out is to use a room humidifier. When an instrument is not in use, it should be kept it in its case along with a small guitar humidifier (of which many are available). Do not leave a guitar out for long periodsnear a heating vent, radiator or other heat source; do not leave it exposed to direct sunlight; and do not leave it in a car for long periods. The general rule is to keep it safe from excessive heat, cold, humidity and dryness.

Cracks in the Wood

Cracks in the wood are typically caused by changes in temperature and humidity. While a crack may initially be alarming, it shouldn’t be a cause for undue concern if it is taken care of promptly. Cracks may be repaired easily without compromising structural or tonal integrity.

If the crack is in the top near the bridge, loosen all the strings to reduce tension (which could potentially exacerbate the problem), and have the crack repaired as soon as possible. Please note: Cracks in the wood, which occur as the result of exposure to temperature or humidity changes, will not be covered under the Guild warranty.


Keep it Clean

Clean the instrument after each use, making sure to wipe the fingerboard and strings, as well as any of the plated parts, i.e., machine heads, pickups, etc., with a soft dry cloth.

For gloss finishes, use a non-silicone based guitar polish. For satin finishes, use only a soft, dry polishing cloth. For hand-rubbed finishes, use a soft, slightly damp cloth and follow with a dry cloth.

When not playing the instrument, keep it tuned to pitch and in its case. However, if you plan to store the instrument for long periods of time, loosen the strings a bit to relieve the tension, but do not remove them.

The natural oils in rosewood and ebony fingerboards may dry out over time. Rough, exposed fret edges are evidence of dry, shrunken wood. It is a good idea to give your fingerboard a drink of raw linseed oil periodically to preserve its integrity and natural beauty.

Remove the strings first; then apply the oil to a clean lint-free cloth. Rub it into the wood, let it soak in, and then wipe to dry any excess oil.

Tuning Machines

Guild uses only the finest tuning machines. These machines are pre-lubricated, die-cast sealed tuners that do not require periodic oiling for smooth operation.

A small tension adjustment screw is located at the end of each tuner’s button that also holds the button in place. If the tension is too loose, the machine may slip and go out of tune easily. If it is too tight, the button may become very difficult to turn. Make sure that the adjustment is firm, but not too tight.

The chrome and gold plating on Guild tuning machines may become degraded from the acids and oils in finger sweat. Wipe the machines off with a soft dry cloth after each use to preserve their appearance and function.

Strings that have not been secured properly to the tuning machine post may easily slip and go out of tune. This problem is commonly misdiagnosed as an issue with the tuners. Check your string installation carefully.

Changing the Strings

A new set of strings can breathe renewed life into your instrument. That is why many “tone-conscious” touring professionals change their strings before every performance. While there is no set rule on how often to change strings, we have found that most players do not change them nearly as often as they should.

Body oils, acids from sweaty hands and humidity all interact with the metals in guitar strings and cause corrosion and breakdown of the materials.

Don’t wait until your strings break and fall off from old age before you change them. Worn, oxidized, pitted and dirty strings will not hold pitch, and they simply sound bad. If you are an average player, playing several times a week, we suggest that you change the strings at least once a month.

When changing strings, we recommend that you remove and replace each string one at a time instead of all at once. This will prevent sudden and potentially damaging changes in neck tension. Each new string should be tuned up to correct pitch before the next one is removed.

When tuning a brand-new string, always bring it up to pitch slowly. Otherwise, the rapid stretching may cause the string to break.

Adjusting Your Truss Rod

String tension exerts a tremendous bending force on the guitar neck. Environmental conditions such as temperature and humidity may also cause bowing of the neck.

Guild guitars have an adjustable truss rod (or dual truss rods on all Guild 12-strings) running the length of the neck that counteracts this force, strengthens the neck and ensures straightness.

A truss rod that is too loose will result in a concave neck bow (action too high); a truss rod that is too tight will result in a convex neck bow (low action and fret buzz).

Should the neck of your guitar require adjustment, first remove the rod cover located on the headstock above the nut (the guitar should remain tuned to pitch during this procedure). Then insert a Guild truss rod adjustment wrench (p/n 350-9521-000) or an equivalent 1/4” nut driver (see illustration 4).

If the neck has a concave bow, tighten the truss rod nut by turning it clockwise. If the neck is humped or has a convex bow, loosen the truss rod nut by turning it counter-clockwise. Adjust the rod only a partial turn at a time, allow time for the wood to settle, and sight down the neck after each adjustment. Be careful not to  over-tighten the rod.

If you meet excessive resistance or if you have any doubts in your ability to make this adjustment correctly, take your guitar to an Authorized Guild Service Center.

Please note: Truss rod adjustments are considered routine maintenance and will not be covered under the Guild warranty.

Adjusting String Action

String height and tension typically determine the ease with which the strings can be depressed. This description of playability is usually called the “action,” and is determined by the distance between the strings and the frets.

Depending on your technique or playing style, high action can sometimes make a guitar difficult to play;  low action may cause string buzz.

Most electric guitars have height-adjustable bridges with adjustable saddles that allow you to easily tailor the action to your preference. On a flat-top or classical guitar, adjustment is somewhat more involved.

To lower the action on a flat-top or classical guitar, the bridge saddle must be removed, cut down to the appropriate height and then re-installed. To raise the action, the saddle must be removed and replaced by a new, higher saddle.

Please note: These types of action adjustments on acoustic guitars should be performed only by an experienced and qualified repairman.

Traveling with Your Guitar

Guild guitars demonstrate the highest standards of quality in material and craftsmanship, and deserve only the best in protection. We recommend that you purchase a Guild factory guitar case that has been designed and fitted exclusively for your guitar to give it the utmost protection. Keep your guitar in its case when not playing it.

If you plan to travel, carry your instrument in a hard-shell case at all times for protection.

When traveling by air, your guitar may be exposed to dramatic changes in temperature and pressure. To help prevent possible damage, de-tune the strings approximately one whole step so that the tension is reduced from the guitar’s top and neck.

Guild offers a variety of standard and deluxe cases for most guitar models. Please contact your local Guild dealer for more information or to place an order.

When ordering your factory case, please specify the exact model of your guitar.

Servicing Your Guitar

New guitars typically have a settling-in period during which adjustments may be necessary to compensate for string tension. Many experienced guitar player have learned to adjust the truss rod or “action” of their own instruments.

If you do not feel comfortable making these adjustments to your new guitar, we recommend that you return the instrument to your Guild dealer or to an Authorized Service Center within 90 days of the purchase for an inspection and truss rod adjustment (if necessary). This precaution should identify and prevent potential damage to the neck.

If major service is requred, please contact your local authorized Guild service center. If you need assistance locating an authorized Guild service center, please visit or your local Guild dealer.

Please note: Truss rod adjustments and action adjustments are considered routine maintenance and will not be covered under the Guild warranty.