Acoustic Guitar Care

If the guitar absorbs too much moisture (humidity beyond 55-60%) it will expand and swell. It can weaken the glue joints and with prolonged excessive moisture, the glue under the bridge can weaken and even pull off.   (Please be careful about storing your guitar in a carbon fiber case while also adding any humidity, it can over humidify it)

The signs of a “wet” guitar are:

– Swelling of top and back
– High Action
– Muffled tone quality – low volume
– Finish Cracks
– Binding separation

Things to consider for storing your guitar in the summer months:

– Don’t keep your guitar in a basement during high humidity
– Don’t keep your guitar in a trunk of a car
– Keep exposure from direct sunlight to a minimum – to avoid premature yellowing of top.

All problems that are caused by high humidity if short term should correct itself when the guitar returns to a normal range of humidity (40-45%) relative to room temperature.

If the guitar is in an overly dry environment with a lack of humidity (under 40%) the wood will shrink and crack. Simple guitar humidifiers in dry regions might not be enough, so make sure you check your room humidity and keep it at 45-50%

The signs of a “dry” guitar are:

– String buzzing – caused by low action
– Bridge lifting
– Finish cracks (below 30% humidity)
– Fret lifting – causing fret ends to stick out from fingerboard
– Dips in the top or back

Things to consider for storing your guitar in the winter months:

– Keep your guitar in a case with a humidity device
– Allow your guitar time in the case to warm up slowly if exposed to cold

If you start to see any of the signs above either in summer or winter take note of the humidity and where the guitar is being stored.

Truss rods are installed in Thompson Guitars to adjust the straightness of the neck. Truss rods may require adjustment when temperature and humidity may have caused the neck shape to change slightly or if string gauges have been changed therefore altering the tension on the neck.

For most playing styles there should be a slight amount of “Relief”. This is the slight forward bow that is seen if you sight down the neck. Typical measurements for instruments strung with medium gauge strings are from .005” to .010”. For instruments strung with lighter gauge strings

depending on playing style there might be a need for more relief from .008” to .014”.Thompson Guitars use a single action truss rod, which is accessible from the sound-hole of the guitar. Current Thompson models use an 1/8” allen head wrench and there is a guide hole in the transverse brace just above the sound-hole inside the guitar. (Some older models may have a

different adjustment requiring a 5/16” narrow “nut driver” wrench).

A simple way of eyeball measuring relief is to place a capo on the first fret and then fret the string at the 12th or 14th fret. The amount of gap seen at the 6th or 7th fret is the approximate amount of neck relief.

Remember there is no exact measurement that will be correct for all guitars. Neck stiffness, top stiffness, string gauge and playing style all vary from one guitar to the next. It is best to have your guitars neck relief adjusted by a qualified guitar technician. If you choose to make a minor

adjustment on your own make any adjustments in very small increments of perhaps a 1/8th turn in either direction. Turning the rod to the right will tighten the rod and therefore add straightness to the neck. Turning to the left or loosening the rod will allow for more bow or relief.

Thompson Guitars are all outfitted with hand made nuts and saddles made of bone. Occasionally we will use an Ebony nut on a smaller guitar such as an all Mahogany size 2, Single 0 or 00. Nut and saddle adjustments are very particular and are specialized to each guitar.

We set up each Thompson Guitar with an individualized nut and saddle before it leaves the shop. Most often the action, height of the strings above the fret board is set to a medium action and playability.

The nuts are set for comfort in playing and most often do not have to be adjusted for playability issues. If the saddle or bridge height is changed beyond a small amount that change can affect the nut. The most common issue is that the saddle action is lowered to the extent that string buzzes occur at the nut. This means that the string slots might need adjustment to

give proper playablity at the nut. The saddle height on a new Thompson Guitar is approximately 1/8” to 5/32” tall. The bridge is approximately 5/16” to 3/8” tall. This generally leaves enough saddle and bridge so that

adjustments can be made to the playability and action of the guitar. New guitars all settle and change for the first few months due to having string tension on the top and neck. Fine guitars are made with thin solid woods that are affected by changes in temperature and humidity. An

important factor to the health of your guitar is to avoid rapid changes in both temperature and humidity. Thompson Guitars are made in a relative humidity of 45% to 50%. It is best to keep your guitar within that range. A good way to think about it is if you’re uncomfortable so is your guitar.

Your Thompson Guitar is built with a top that is radiused to 52’. We expect that the top of the guitar will move up as string tension brings the top up. This is normal and a good sign ,as the guitar sounds so good because the top is ready to perform. If however the guitar is exposed to

excess humidity the guitar will swell in addition to the tension on the top. This will cause the action to come up and if the conditions persist you may want to have the action adjusted. We strongly recommend that this work be done by a qualified guitar technician. A very small adjustment to the saddle or bridge height can have a large effect on the action. The average action specs that we send guitars out with are between 4/32” at the 12th fret for

the low E string and 3/32” for the high E string.

String Action and playability as well as truss rod relief are all set to standard A440 Hz tuning. If you live in an area where humidity changes dramatically between summer and winter (humid in summer, dry in winter) you may want to have a couple of saddles made so that you can adjust the action simply by changing out the saddle. After anywhere from one to three years

most guitars will stabilize to the point that the action is effected less and less by climate changes. Still keeping the guitar within acceptable limits with humidity and temperature are key

to the long- term health and performance of your guitar.

If you have questions or your guitar technician has any questions regarding the set-up and performance of your Thompson Guitar please call us and we are happy to answer your questions and discuss these any other factors that are important to the playability of your Thompson Guitar.

In the early 20’s Nitrocellulose lacquer became the preferred finish on high-quality furniture and musical instruments. It is an exceptionally fast-drying solvent finish and a stronger version of the original shellacs and varnishes and is what we use on our guitars.

Nitrocellulose lacquer can be applied in multiple coats, but the resulting finish is still thin and protective. Because of its glass-like quality, it does a superb job of showing the beauty and grain of the wood. Also because it is such a thin finish it does not inhibit the natural sound of the guitar.

Compared to the more modern day polyester finishes it can be affected by solvents, alcohol, certain acids and other substances, care should be taken to avoid prolonged exposure with any of these.

Nitrocellulose lacquer buffs to a high gloss and has a softer sheen, which may, in turn, show more wood grain compared to thicker poly finishes.

A brand new guitar with a nitrocellulose finish will be shiny and beautiful, but over time as the guitar is played the finish will begin to age – for example; swirl marks created by sitting the guitar on different surfaces or just holding it and playing it. If you are very particular about your finishes even shirt buttons and belt buckles will mare the finish, however, this creates the character of each individual guitar.

This type of finish, as it dries over time, creates a warm vintage patina something you see in guitars from the Golden Era. Sometimes because of climatic changes, you will see small finish checks or alligatoring of the thin finish, but this does not affect the integrity of the guitar or the protective nature of the finish.

The best way to care for this finish is to clean your guitar with a damp warm soft rag and/or a very quality guitar polish that does not contain silicones.

At Thompson guitars, we take pride in applying the highest quality finish to help set the stage for that vintage quality and tone.

When shipping your guitar make sure you put the guitar in a case and then a guitar box with packing material. Take the string tension off of the strings and place a humidifier in the guitar if traveling during cold months or from a wet climate to a dry climate. If there is any movement between the body of the guitar and the case add in some crumbled newspaper in between case and guitar so it doesn’t move while in the case.