How to Properly Humidify Your Acoustic Guitar (And Get Accurate Readings!)

Updated at: 05/06/2025

The rich, resonant tone of an acoustic guitar is a delicate balance, easily disrupted by fluctuating humidity. Wood, the very heart of your instrument, is a living material that expands and contracts with the surrounding moisture levels. Neglecting proper humidification can lead to cracks, warping, and a compromised sound, ultimately diminishing the lifespan and value of your prized possession. Maintaining optimal humidity is crucial, but achieving accurate readings can be surprisingly tricky. Incorrect measurements can lead to over- or under-humidification, both equally detrimental to your guitar.

This article will guide you through the process of correctly humidifying your acoustic guitar, ensuring its health and preserving its exquisite tone. We'll cover everything from choosing the right humidifier and hygrometer to understanding how to interpret the readings and avoid common mistakes. Let's dive into the step-by-step process that will keep your guitar playing beautifully for years to come.

Preparation and Safety Guidelines

Tools Needed

Hygrometer
Plastic bowl
Rag
Something non-absorbent to cover the sound hole (plastic, plate, etc.)

Safety Guidelines

Never place your guitar directly on a humidifier. Always use a humidifier designed for acoustic instruments and follow its instructions carefully.
Over-humidification is as damaging as under-humidification. Monitor humidity levels regularly using a reliable hygrometer and adjust accordingly. Aim for the recommended 45-55% relative humidity range.
Extreme temperature changes can negate the effects of humidification and cause damage. Avoid placing your guitar near heat sources or in direct sunlight.

Step-by-Step Instructions

Check Current Humidity
- Check humidity levels using a hygrometer.
- Place the hygrometer inside the guitar's sound hole, covering the hole with a non-absorbent material.
- Leave the hygrometer in place for 28-48 hours (longer is better for accuracy).
Check Current Humidity
Humidify the Guitar
- To humidify, place a soaked rag in a small plastic bowl inside the sound hole.
- Cover the sound hole with a non-absorbent material.
- Leave the humidifier in place for at least 48 hours (or longer).
Humidify the Guitar

Tips

The reading from the hygrometer after 28-48 hours gives a true measure of the wood's moisture content, not just the air inside the case.
For accurate readings, leave the hygrometer in place for a longer period, even up to 72 hours.
Ensure the material covering the sound hole is non-absorbent to prevent inaccurate readings.

Common Mistakes to Avoid

1. Using an inaccurate hygrometer

Reason: Many inexpensive hygrometers are unreliable and provide inaccurate readings, leading to improper humidification.

Solution: Invest in a calibrated digital hygrometer or a reliable analog one with salt calibration.

2. Over-humidifying the guitar

Reason: Too much humidity can cause the wood to swell, leading to cracks and warping.

Solution: Maintain humidity levels between 40-60%, checking regularly and adjusting as needed.

3. Incorrect placement of humidification devices

Reason: Placing humidifiers too close to the soundboard can cause uneven moisture absorption, damaging the instrument.

Solution: Place humidifiers inside the guitar case, but not directly touching the guitar or soundboard.

FAQs

What's the ideal humidity level for my acoustic guitar?

Ideally, you should aim for a humidity level between 45% and 55%. This range keeps the wood properly hydrated without making it excessively damp, preventing both cracking and warping.

My hygrometer shows different readings than my humidifier's sensor. Which one should I trust?

Trust your hygrometer. While humidifier sensors provide a general idea of the chamber's humidity, hygrometers (especially digital ones) are designed for more accurate ambient readings inside the guitar case. Place your hygrometer directly inside the case with your guitar for the most accurate measurement.