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As a luthier, you put in hours of detailed work on intricate parts. Imagine the frustration of coming to your workshop one morning and finding a warped or twisted guitar fretboard.

Not only does that guitar represent many hours of your precious time. It also represents a considerable amount of money on valuable wood—and your customer’s confidence.

luthier chiseling a violin

With the significant time and effort that goes into building a musical instrument, preventing moisture damage is vital to protect that investment.

At least the problem has occurred before it goes to your customer. But what if you delivered a finished product to your customer, only for them to call you about damage a couple months later? Now, in addition to wasted time and money, your customer’s confidence is waning.

Wouldn’t it be so much better to protect the instruments against this damage in the first place?

That’s what keeping your wood at the right moisture content can help you do. We’ll cover everything you need to know about moisture testing, including:

Why Luthiers Need a Moisture Meter

A moisture meter helps you know your wood’s moisture content (MC) so you can ensure it’s dry enough before use. Otherwise, you risk moisture damage.

Wood adjusts to the moisture of its environment, gaining or losing moisture depending on whether the relative humidity is higher or lower, respectively. Once you’ve built a wooden instrument, large amounts of moisture gained or lost can cause expansion or shrinkage in the wood. These shifts, in turn, can affect the instrument’s structure, sound, and quality.

For example, a guitar with too high of an MC, when placed in a drier climate, may end up with shrinking components (and maybe twisted, or bowed, depending on the grain pattern and orientation) or cracking in other places.

On the flip side, the expansion of a guitar could cause glue to come apart or the wood to warp.

Tom Bills, who’s been building professional guitars by hand since 1998, has a lot to say about the effects of moisture on guitars:

“The edges of the guitar top are all glued in place to a ridged side structure. When the top plate tries to shrink (as it loses moisture into very dry air) and the sides are stuck in place it has no choice but to rip itself apart and crack. This type of cracking is commonly known as ‘checking.’

“Conversely, if the guitar top plate tries to expand as it absorbs water from overly humid air it will again be restricted by the fixed ridged guitar sides it is glued to and will have no choice but to bow upward in the center.”

For these reasons, luthiers must know the moisture of the surrounding environment (known as the equilibrium moisture content, or EMC) so they can make sure the wood has reached that number. A moisture meter will help you know the MC of your wood in relation to the EMC.

The Best Moisture Meter for Luthiers

The best moisture meter will give you quick and accurate readings without damaging the expensive wood you’re working with.

There are two main types of moisture meters—pin and pinless—though we definitely recommend pinless when you’re working with instruments. This way, you won’t damage the wood with pinholes.

Pinless moisture meters will also work best with the dense hardwoods often used for building instruments. Rather than trying to push pins into the wood, you can quickly and easily scan the wood.

Here are some other features to look for:

  • Species settings: The moisture meter should have plenty of species settings for the unique types of wood you’ll be working with as a luthier.
  • Dual-depth: A dual-depth moisture meter usually allows you to measure both ¼”-thick and ¾”-thick wood. You’ll be able to scan wood used for both thinner and thicker parts of the instrument.
  • On-site calibration: This feature allows you to calibrate the device with the press of a button. No need to send the device back to the manufacturer!
  • A good warranty: A good warranty speaks to the quality of the meter. Typically, 2 years is a solid warranty.

At Moisture Meter Experts, we’ve tested the most well-known wood moisture meters on the market.

Our top four choices are from Wagner Meters’ Orion line. We’ll lump them together for the purpose of this article.

These meters are accurate down to 4% moisture content. Many of them also include dual-depth settings and an on-demand calibrator. And all Wagner’s meters have a 7-year warranty!

The Orion 950 has even more benefits for luthiers. It includes temperature and humidity sensors that calculate the EMC. And, it has Bluetooth connectivity so that you can collect all your data on your smartphone app—a good way to keep records when you’re working on many projects for customers.

Another solid moisture meter is the Lignomat Scanner D. It’s accurate from 5 to 13% MC, has a built-in species correction feature, and offers a 2-year warranty.

Any one of these meters will suit your needs as a luthier, though the deciding factor will be the features that are most important to you.

Let’s look next at how a moisture meter can play a part in protecting your wooden instruments.

Best Practices for Protecting Wooden Instruments from Moisture

The foundation to avoid catastrophic warping to your hard work is understanding the concept of equilibrium moisture content (or EMC). Then, you’ll be able to use a wood moisture meter accordingly and keep your wood at the proper moisture content for its environment.

So what is equilibrium moisture content?

This is the moisture content that wood will reach at a particular temperature and relative humidity. And every region has a specific EMC to which wood must adjust before you build with it.

So, how do you find out the EMC?

Determine the EMC of the instrument’s final location

Don’t worry—you don’t have to use any complicated formulas. It can be as simple as using an EMC chart based on the typical temperature and relative humidity for the final location of the instrument.

Keep your guitar at a stable temperature and relative humidity so that it looks and sounds its best.

The ideal MC for your wood will be at or near this EMC. Typically, for controlled indoor environments, this will be 6–9% MC at a relative humidity of about 45–50%.

This is what instrument builder Scott MacDonald aims for. “I feel this is perfect for joinery and all aspects of guitar making,” he says.

Tom Bills, whom we mentioned earlier, recommends 9% moisture content for an environment at about 72° F and 50% relative humidity. He says this is a good average no matter where a guitar may end up in the world.

Check the moisture content of the wood

Once you know the EMC for the instrument’s final location, use your wood moisture meter to check your wood.

You’ll want to check the wood before purchasing it (if possible) and before working with it.

Here are some tips for getting accurate moisture readings:

  • Check the meter’s calibration with the provided calibration block or use the on-demand calibrator (if your meter has one).
  • Input the correct wood species number.
  • Make sure you’re using the correct depth setting.
  • Scan the wood moisture meter on a flat surface, using about 2 pounds of pressure.

If the MC of the wood is significantly above the EMC, you may need to air dry it or kiln dry it (depending on how big of a rush you’re in).

Keep your wood in a consistent environment

Storing tonewood and finished instruments at a consistent temperature and humidity is crucial for preventing warping.

You’ll want your workshop to be at a point somewhere between 45 and 50% relative humidity and 60 and 70° F.

Here’s something to keep in mind too:

Wood can usually handle expansion better than shrinking.

Thus, if a guitar is built in a high-humidity environment (say in Florida) and then goes to a drier climate (like Arizona), it’s more likely to crack as it shrinks.

To avoid this, determine the average of the high and low humidity levels in the final location. Then, keep the guitar in an environment with an ever-so-slightly lower humidity than that.

A hygrometer can help you keep track of these levels in your workshop. Adjust the humidity levels with a humidifier or dehumidifier as needed, particularly as seasons change.

Frequently Asked Questions

Still wondering about moisture and wooden instruments? See if some of these common questions and answers help:

What is the ideal moisture content for guitar building?

The typical ideal moisture content is between 6 and 9%, though the exact number will vary slightly depending on the equilibrium moisture content of the final region. Determine this number with an EMC chart based on relative humidity and temperature.

Is 30% humidity okay for guitars?

This humidity level is quite low and could lead to splitting, cracking, or other damage. Taylor Guitars recommends a relative humidity of 45–55%. If you’re in a dry climate, consider using a humidifier for your guitar and keep it in an indoor environment with balanced humidity levels.

What factors should I consider when selecting a wood moisture meter for my lutherie needs?

We recommend finding a highly accurate pinless wood moisture meter so your wood won’t be damaged when you take readings.

Some other factors to consider are:

  • Dual depth readings, so you can measure different thicknesses of wood
  • Species settings, so you can adjust readings for the species you’re measuring
  • A calibrator to verify that you get the most accurate readings
  • A good warranty (at least 2 years) to show you that the company stands behind its devices

Sleep Well Knowing Your Wooden Instruments Are Safe from Moisture

With so much at stake as you build a wooden instrument—your time, expensive materials, and customer expectations—don’t allow moisture to sabotage your project. Investing in a high-quality moisture meter can help ensure your wood is at the right MC.

This way, you’ll protect your hard work and reputation. And you can sleep well at night without worrying about moisture damage.

Check out our latest moisture meter reviews to find the best option for your business.