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Acoustic Guitar Maintenance

Most of us should probably take better care of our acoustic guitars. Considering the value we place on them, it’s surprising how few of us do. In the following guide, we’re going to take a closer look at acoustic guitar maintenance, including several easy maintenance tasks you can do yourself without specialist tools or experience. We’ll also discuss which jobs are better handled by a luthier. So if your guitar is in declining health, or just feels harder to play, stay tuned!


This guide is part of a larger series of articles that helps introduce people to the acoustic guitar and includes the following articles:

Don’t have time to read the full article? Check out our quick maintenance checklist below:

Acoustic guitar maintenance checklist

  • Control humidity
    Between 45% and 55% is ideal.
  • Keep the guitar clean
    • If the fretboard is unsealed use fine grade steel wool and remove gunk around the frets with a toothpick.
    • Clean the body using warm water (no household cleaners) or lighter fluid (won’t harm the finish).
    • Keep hardware e.g. tuners clean
    • Maintain your strings
  • Condition the neck and bridge (if unsealed)
  • Keep tuners maintained
  • Have the guitar setup
    Done as required e.g. playability issues
    • Check neck relief by adjusting the truss rod
    • Check action by adjusting the saddle and nut
    • Check intonation
    • Check fretwork
    • Fret dressing
      • Fret leveling, recrowning, and polishing
    • Nut Maintenance
    • Restring the guitar
    • Wipe down the guitar after use

A checklist can be handy, but if you are keen to get your hands dirty the information below will explain each of the steps listed above in more detail, including providing links to additional resources.

Ok, with that out of the way let’s dive into one of the more interesting aspects of guitar maintenance, humidity.


Controlling Humidity

Hygrometer
A hygrometer. Used to measure relative humidity

Your guitar is almost completely made from wood. Wood, is ‘hygroscopic’ aka absorptive, meaning it holds or loses moisture content in line with the relative humidity of its surroundings.

The amount of moisture wood is capable of holding is known as its equilibrium moisture content (EMC). Wood can take up to three days to fully acclimatize and reach EMC.

Ideally, acoustic guitars should be kept between 45% and 55% relative humidity. Martin & Co maintain relative humidity between 45 and 55% in their factories and advises store owners to do the same. Taylor keeps theirs locked in at 47%. If your guitar is kept in an environment with high relative humidity the cells in the timber will expand due to taking in moisture. This can ‘deaden’ acoustic guitars e.g. the guitar will sound dull and feel unresponsive.

Alternatively, if the guitar is kept in a very dry environment, it will quickly lose moisture as the cells in the wood contract. And while a ‘dry’ guitar will sound more resonant than a ‘wet’ guitar, if allowed to dry excessively, at its most extreme, your acoustic guitar might develop cracks in the soundboard, along with other structural issues including sharp fret ends as the wood in the neck contracts, loose bracing, and changes to neck relief. All of which can then affect playability, tuning stability and intonation.

To counter the effects of humidity, you must first measure the relative humidity with a hygrometer, and then control humidity through the use of a humidifier.

If you are unsure of what a hygrometer is or how humidifiers work and which is best for your situation you can read all about how to do this here, including tips on how to store your acoustic guitar at 45% – 55% relative humidity.

Rapid Temperature Changes
While not a maintenance issue, another environmental concern that can cause problems for acoustic guitars is rapid temperature changes. This mostly concerns going from a particularly cold environment to a warm environment. If you left your guitar in the car overnight for example and happen to live in Canada, it’s best to let the guitar acclimatize for 2-3 hours before opening the case. While less likely to cause structural problems, in some cases, rapid fluctuations in temperature may damage the finish of the guitar.


Acoustic Guitar Cleaning and Conditioning

We all like our guitars to look good, well most of us do.

Willie Nelson and “Trigger”
Willie Nelson and “Trigger”

But, cleaning the guitar is about more than mere aesthetics.

For example, if your fretboard builds up with gunk from your hands, the salt residue contained within sweat can cause damage to wood over time. This is especially the case for untreated fretboard woods such as Ebony and Rosewood. This can cause your fret wires to become loose, not to mention tarnishing your frets.

While that might sound like a good reason to clean your hands before you play guitar, and it is, you should also clean the fretboard 2-3 times per year to prevent build-up, and wipe down the guitar after playing.

Cleaning the Body and Hardware

Cleaning a guitar Body with lighter fluid

You should also keep the body of the guitar clean. In most cases, I’d recommend using a microfibre cloth or polishing cloth and warm water.

If your guitar body has a nitrocellulose (most common) or polyurethane finish you can use lighter fluid, as this is a gentle solvent that will break down and remove most residual gunk from the body of the guitar, including sticker residue. Test first if using on varnish and shellac finishes, however.

You should also clean your hardware. Keeping components such as your tuners clean, prevents them from building up with gunk around the gears and helps keep them in good working order. Most of the time (unless dealing with a vintage instrument) lubricating your tuners isn’t necessary but keeping them clean using a small amount of lighter fluid applied with an old toothbrush will keep the gears ticking over nicely.

Conditioning

It’s also a good idea to condition the fretboard 2-3 times per year to ensure it doesn’t dry out. This isn’t required if your guitar has a sealed maple neck, but the majority of fretboards (and bridges for that matter) are unsealed and therefore keeping them conditioned helps reduce the possibility of cracks developing.

F-one fretboard oil from MusicNomad is the product I use. It’s lemon and petroleum-free, which is important, as both can dry out your fretboard.

You can read my full guide to cleaning and conditioning acoustic guitars here which goes into far more detail.


Keep tuners maintained

As tuners age, the gears (or more accurately the teeth of the gears) that drive the tuning mechanism begin to wear down, and friction on the gears and worm drive is gradually lost. When this happens the tuners will begin to slip, making it difficult to tune as tension increases.

Keeping them clean will prevent a build-up of corrosive gunk that would otherwise speed up this process.

While some older instruments can benefit from lubricating the tuning gears with machine oil, most newer guitars don’t really require this provided they are otherwise well maintained.

Loose Screws

Aside from keeping the tuners ‘gunk free’ you should also check for loose screws. While a problem in terms of securing the tuners on the headstock, they might also be the reason you are hearing vibrations when you are playing.

Start with the tuner bushings and washers (unless press-fit bushings). These are usually 10mm in diameter. A useful tool I have used many times for tightening tuner bushings is the Music Nomad Octopus 8 in 1 tool, made from hard nylon to prevent scratching the guitar.

Tighten, but don’t over-tighten or you may find the bushing leaves an indent in the headstock’s finish, or you round off the edges of the bushing.

Other times due to changes in humidity and the wood of the headstock contracting and expanding the screws securing the tuners to the headstock can become loose. The tuner button screws securing the button to the tuning post can also become loose especially on older guitars.

While all loose screws should be tightened, you should also avoid over-tightening.

Acoustic Guitar Tuning Peg

For one, the screws used for your tuners are small and in many cases easily stripped. Secondly in the case of the tuner button screw, when tightened the button rests against a washer (see image above) that is used to control the amount of friction e.g. how easy or hard the tuning button is to turn.

If you over-tighten the tuner it can become much harder to turn and the washer might also split. If too loose, tuning stability may be affected.


Guitar Setup

A guitar setup mostly involves the neck and includes checking and adjusting the guitar’s neck relief, maintaining the nut, checking and adjusting the guitar’s action and intonation, and maintaining the fretwork.

Bridge maintenance is also something that should be done periodically, including conditioning the bridge and replacing loose or damaged bridge pins.

But for the most part, all setups begin with the truss rod.


Adjusting Neck Relief using the Truss Rod

Acoustic Guitar Truss Rod

Guitar necks are put under a lot of tension from the guitar’s strings. To help distribute the load and maintain structural integrity a truss rod is installed in the neck which can be adjusted to provide your guitar’s neck more or less relief as needed.

If the action is particularly high, reducing the amount of neck relief can help. Alternatively, if the strings of the guitar are buzzing against the fret wires (fret buzz) it’s likely the neck of the guitar doesn’t have sufficient relief and needs adjusting via the truss rod.

Truss rod adjustment needn’t be scary, but you should read up on how it’s done so you can avoid running into problems. I’ve written a detailed guide here that explains everything you need to know about truss rods, so be sure to check it out.


Checking your Action

Measuing action with a string action ruler at the 12th fret.
Measuring action with a string action ruler at the 12th fret. Between 2.5 and 2.8mm is recommended in most cases but depends on your playing style.

Action refers to the space between the underside of your strings and the fretboard.

Setting your action is usually a bit of a compromise between playability and tone. For example, most of us find a guitar with a low action easier to play, especially when playing fast.

But, setting your action too low might also result in fret buzz. It’s also true that the higher the action is, the more resonant the guitar often is, which results in greater projection (the speed sound travels), volume, and sustain, but as we will discuss shortly this can also affect intonation.

While neck relief certainly plays a role, action is mostly dictated by the height of the bridge saddle and nut, as these are the two endpoints the guitar string is suspended between and establishes the scale length of the string.

On electric guitar, string action is easily taken care of by changing the position of the adjustable saddles but on acoustic guitar, we don’t have this luxury and instead need to either add material e.g. a shim under the saddle or remove material, to lower the action.

Depending on the action at the nut, which depends on the height of the nut and the nut-slot height, you may also choose to shim or remove material from the nut, which unlike the saddle which is held in place by the strings takes a little more work to remove. But for the most part, requires a sharp blade delicately worked between the nut and headstock to break the seal of the glue holding it in place. In most cases, once the seal is broken the nut pops right out.

Once removed, it’s merely a case of adding material in the form of a shim. A sliver (e.g. 1mm) of rosewood is ideal (avoid materials that will absorb any of the vibrations from the strings) or sitting the saddle and/or nut flat against medium grade sandpaper and removing the excess.

Failing that, you could also simply order a new nut and saddle but make sure you order a nut with the correct nut width for your guitar, and if your saddle is a compensated saddle keep this in mind when ordering.

Measuring String Action

A handy tool to measure string action is, surprisingly, a string action ruler due to its compact size but in a pinch, any reliable steel ruler will do the job.

String Action Ruler

It’s best to measure action at the 12th fret. On acoustic guitar, action is usually set between 2.5 and 2.8mm but is dependent on playing style to some degree.

For example, if you play with a light touch you may get away with a lower action than this, however, if you strum big open chords, or play slide guitar, you might want a higher action. There are no rules, as long as the guitar suits your playing style.


Checking Intonation

Intonation refers to pitch accuracy. The easiest way to test intonation is to tune your guitar to concert pitch and then test the tuning of any open string compared to how in tune it is at the 12th fret harmonic.

If you find the note is sharp, the scale length (string length between the nut and saddle) of the string must be increased. If the note is flat the string length must be reduced, as when a guitar string is shorter it vibrates faster, when longer it vibrates slower.

This is all well and good on electric guitars which usually feature adjustable saddles that can be moved back or forward on the bridge but on acoustic guitars all we have is the placement and adjustment of the saddle.

Compensation

Angled bridge - Intonation

You might have noticed your saddle is slanted. While the center of the saddle is where the scale length of the instrument is usually measured. The slanted bridge lengthens the bass strings, providing compensation for their additional mass

This is more noticeable when playing in higher positions on the neck, as the additional mass of your bass strings (thicker core + windings) affects string tension. For classical guitars, as there is less of a difference between the mass of the individual strings the saddle usually isn’t slanted.

Compensated Saddles

Compensated saddle
A Compensated Saddle

You might also notice your saddle isn’t strictly uniform (see example above). Many acoustic guitar saddles are compensated. This means the treble side of your saddle has material removed from the back of the saddle to push the point of contact for the stings forward, thus shortening the strings ever so slightly. The opposite is true on the bass side.

So, while acoustic guitars don’t feature adjustable saddles (it’s never a good idea to add metal to soundboards as resonance will be affected) quite a bit of compensation is already in place to account for intonation.

But what if your intonation is still out? How is intonation adjusted on acoustic guitars?

Neck Relief

The first place to start is with your neck relief. If the guitar has a significant inward bow, the action near the 12th fret is likely to be high. This additional distance between the fretboard and string results in more tension being placed on the string when fretting a note which can cause notes higher up the neck to be sharper.

It’s also true that when relief is increased the string length decreases and when relief is reduced the string length increases. While that happens for all strings it tends to accentuate the differences.

Adjusting the Saddle

Aside from adjusting the truss rod, the last thing you can do is take the guitar to a luthier and have the guitar intonated. This involves making fine adjustments e.g. removing material from the bridge strategically. Otherwise, try a different saddle or different gauge strings.


Checking the condition of the Frets

The fret wires of your guitar will show signs of wear due to the impact of the strings. In some cases, you might notice specific notes fretting out (dead notes), changes to note definition, intonation issues, and less sustain, all of which can be the result of fret wear.

When your frets become especially worn the guitar will require fret dressing to sound and play its best. Fret dressing is a job (usually carried out by a luthier) or someone with experience.

What is fret dressing and why does it require a luthier?
While anyone with a fret leveling beam and crowning files could attempt a fret dress, it’s a job that really should be carried out by someone with experience. Fret wires are unforgiving. If things go badly e.g. too much material is removed, you might require a complete refret of the guitar, costing around a hundred dollars, plus additional setup costs.

Fret dressing is a combination of three separate jobs, including:

Fret Leveling

Fret Leveling Beam and Notched Straight Edge

Fret leveling is carried out with a levelling beam, which is a steel straight edge with sandpaper fixed to the underside of the beam.

Fret leveling, as the name implies, involves ensuring the frets are level with one another. This requires truss rod adjustment first to ensure there is no relief in the neck.

To check if your frets are level, you’ll need a couple of tools. First, a notched straight edge to check the neck is flat. The notches sit over the frets allowing you to check neck relief and usually come in both a 24.75” and 25.5” scale length.

Once the neck is flat, the frets are marked with ink (a sharpie is usually a good option) and filed with a leveling beam until no ink is left remaining on any of the frets. The ink is used to identify low frets. For example, if the fret wires are all marked and after leveling one or two still have ink remaining, we can identify these frets as being lower than the surrounding frets.

The higher frets, from approx. the 15th fret up are often filed on a downward angle getting lower toward the 20th fret. This is to take into account the wider vibrational arc of the strings, which we addressed the cause of earlier when discussing neck relief.

Checking the height of individual frets

Fret Rocker

If you suspect you only have 1-2 uneven frets you can check them using a fret rocker. Rather than taking your leveling beam and filing all the frets at once, a fret rocker allows you to spot uneven fret heights, adjacent to one another.

I’ve already covered the use of fret rockers here, so won’t go into too much detail, suffice to say the name is more literal than you might assume as you literally rock the fret rocker back and forth between three frets at a time.

If you hear a knock, you know the center fret of the three being checked is higher than one or both of the adjacent frets and should then be marked with ink for leveling.

While I don’t recommend fret leveling unless experienced, knowing which frets are high can be useful to know.

Fret Crowning

Fret Crowning Tool

Frets are made up of a tang (the main shaft of the fret), a barbed section, and the crown which is the name given to the top of the fret wire.

When the frets are leveled the crown gets flat and this increases the point of contact for the string when a note is fretted. A narrower point of contact is preferred as this reduces the chances of the guitar having intonation problems.

In simple terms, the top of your frets are crowned through the use of crowning files (three-sided file or specialist crowning tool as shown above) to make the point of contact narrower. The fret ends are also rounded at this stage, to prevent sharp fret ends and to make the guitar more comfortable to play.

During the crowning process, the fretboard must be protected and is often masked, or fret guards are used.

Fret Polishing

Lastly, the frets are polished. After leveling and crowning the frets are no longer smooth and this creates friction between the strings and fret wires, affecting slides and bends.

To polish the fret wires, first, protect the fretboard and then polish using very high-grit sandpaper e.g. 1200 – 1500 grit, followed by fine grade steel wool. The process is usually completed by applying a polishing compound or using fret erasers, like these.

While fret leveling and crowning are specialized jobs, provided you take care not to remove too much material, fret polishing is a job most of us can safely include in a guitar maintenance routine.


Nut Maintenance

The height of your nut and nut slot height determines the action at the first fret. Like fret dressing, I wouldn’t recommend messing around with nut slot filing unless you have some experience and the necessary files.

Each nut slot should be at a sufficient depth to allow the strings to clear the first fret, without raising the action too high and making the guitar difficult to play.

String clearance at the first fret is mostly personal preference but should be in the vicinity of .02” at the low E string and .20″ at the high E string. This can also be measured with a string action ruler or feeler gauge.

You should also clean the nut as needed using lighter fluid and fine-grade steel wool. Don’t use steel wool for the nut slots themselves however as they are abrasive and will affect the nut slot height. Instead use dental floss or a fine, stiff brush.

Lubricating the nut slots

Lubricating the Nut Slots

It’s also a good idea to lubricate the nut slots. This helps with tuning stability as it reduces friction and prevents the strings from dragging. There are dedicated products you can use, but one simple option is to take a lead pencil and add graphite to the nut slots which is an effective nut slot lubricant.


Restringing

If your guitar has been set up it will come with a fresh set of strings. If doing it yourself, once you have completed the tasks listed above you will need to restring the guitar.

Now is not a good time to make big changes to the gauge of string you use, unless happy to keep adjusting the truss rod, as those fine adjustments made earlier were made based on the gauge of the string used previously.

When it comes to restringing the guitar, there’s more you can probably do to aid tuning stability. I was once shown a method of restringing, that I still use to this day that provides the right amount of excess string on the posts and increases the break angle across the nut. This increases tuning stability and may even improve sustain, although the jury is mostly out on the last point.

I’ve written a full guide here if interested in learning how this is done.


Wipe down your guitar after Playing

Lastly, while perhaps obvious, one of the best maintenance tips I can give you is to simply wipe down the guitar after use. Salt residue from the sweat from your hands is the most corrosive thing your guitar will come into contact with. This becomes even more of a problem if you play live under stage lights or are a heavy sweater.

Wiping down the guitar will preserve the life of your strings, help maintain your fretboard and keep your tuners in good working order. Use a microfibre cloth and get in the habit of wiping down the guitar every time you play it.


Summary

While maintenance is usually a fairly dry subject. In the case of guitars, you can often see, hear and feel the benefits of keeping your guitar in top working order almost immediately. Small changes to neck adjustment, cleaning the fretboard, polishing the frets, or taking your guitar in for a full fret dress can give your guitar a whole new lease on life.

So, if you’ve recently found you’re not feeling as inspired to play, or the guitar just feels harder to play, it might not be you, it might well be the guitar, in which case you just need to treat it a little better. Hopefully, the advice above will help you get started.

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About Marty

My name's Marty, I've been into guitars for over 30 years. Theacousticguitarist.com is my blog where I write about acoustic guitars, music, and home recording.