Hi folks. Where I live, the heat is well on its way and for many of us that means more humid weather. This also means turning on the air conditioning for lots of folks, and many people don’t realize that air conditioning can really dry out your instrument. Of course so can heating systems, particularly dry heat based systems and so maintaining proper humidity is a year round responsibility.

What’s The Risk?

Instruments made of wood need to be protected against drying out. Metal instruments, less so, although attention may be needed to be applied to valves to prevent drying. Instruments using laminated wood products are less impacted but still require decent humidification, so inexpensive guitars using laminated layers (plywoods) and drum kits are also at risk. When a wooden instrument dries out, it shrinks, can warp or twist and in bad cases will start cracking. The very thin acoustic tops on instruments are at particular risk.

What is Acceptable Humidity?

For musical instruments, it is recommended that the humidity where the instrument lives be between 40% and 60% relative humidity. You can get digital meters very inexpensively on Amazon and the like, and I would say, these are a must have. Note that the more humidity in the air, the warmer the air can feel in summer, and the colder and damper it can feel in winter. 40% is comfortable for most humans and pets, but over 50% can be uncomfortable for some, particularly if excessive humidity impacts respiratory disorders.

Humidification in the Case

Some instruments come in hard cases and there are many makers who build case humidifiers. This is an effective idea, so long as you remember that it is the instrument that needs humidity not the plywood or plastic of the case. Be aware that most all cases are shipped from the factory with a packet or two of silica gel in the case, designed to keep the case dry. Dispose of this little killer before putting your instrument in the case.

If the case is soft, it likely does not provide a good moisture seal and many gig bags, are to put it bluntly, just garbage. A top line gig bag like a MONO makes a lot of sense if you prefer gig bags, but even if you don’t an in case humidifier is a good thing.

Recognize that all in case humidifiers need regular maintenance so they always maintain humidity. Also note that the more porous the sponge involved, the more often the humidifier will need refilling. When they dry out, they suck moisture out of the instrument.

Sound Hole Humidifiers

These can be great if the unit seals the soundhole. If not, they do nearly nothing if the instrument is not in the case. When they dry out, they suck moisture out of the instrument. If you use one and do not set a schedule to keep them wet, there is no point at all.

The Cold Season

The amount of humidity in the home during the cold season can very enormously. Residences with electric heat tend to be drier due to the lack of any kind of forced air movement and the inability to add a humidifier to the heating system. Even natural gas or propane heat need added humidification and if you heat via fireplace or stove, if the wood or pellets are very dry, they too will suck moisture out of the air. If you have a forced air system, you want to have a humidifier attached to the system. Be sure to change its filter at the beginning and at least once more during the season when it runs. If you have hard water where you live, more frequent filter changes are necessary. If you have electric heat either in room humidifiers or so called whole home humidifiers are necessary. Note that these devices need to be checked for sufficient water in their tanks to be effective. A ‘whole home” humidifier can do a decent job in an apartment but won’t cut it in a house with multiple doorways, hallways and definitely not multiple floors.

If you have forced air heat ensure that your humidifier is running and crank it up if your instruments are on hooks or out of their cases. Most units will not achieve relative humidity of over 40%, so be prepared to supplement. If not on forced air, get a room humidifier for every room where instruments are kept.

The Hot Season

Air conditioning provides cooling through evaporative properties. They suck moisture out of the air. A central air system set to a comfortable cool temperature will rapidly reduce premises humidity to less than 20%. If you have forced air based AC, your forced air humidifier is not doing any good when the AC is running. Summer with air conditioning is very hard on instruments, and so you need to attend to either in case humidifiers or in room humidifiers.

Note that to get the humidity in a room to a level suitable to maintain an instrument, it means that the AC will not feel to be working as well, and the harder it works, the more often you will need to refill the tanks on your humidifier.

Impact of Inadequate Humidity

Acoustic instruments are excellent indicators of too low humidity, but electric instruments suffer as well.

One of the easiest ways to determine if there is insufficient humidity is to check for fret sprout. The frets are not actually growing, but the fingerboard and neck are shrinking due to drying. I always check for fret sprout before buying an instrument because so many are now arriving from factories where the QA process has ignored that the necks were not properly dried before installing the frets. Get your guitar shop to fix this before you take the guitar home, or if you just bought a guitar used with serious fret sprout, after humidifying it for a week or so and the problem is still there, get it to a qualified technician. Spending a lot of money on a guitar does not mean that there will not be fret sprout. I have found $4000 guitars from Fender with horrible fret sprout and $500 EART guitars shipped in a box from China to Amazon that were perfect. To find fret sprout run the pad of your fingertip down the side of the fretboard keeping the finger parallel to the edge. If you feel sharp fret ends, you have fret sprout. If a guitar that did not have fret sprout in the past, has it now, you have a too low humidity issue. This is as true for electrics as acoustics.

Remember that a guitar of any type that gets too dry is prone to shrinking, cracking, twisting and warping.

If you find that your acoustic guitar sounds brighter than in the past, and you have not just restrung it, this indicates that the guitar is too dry. The same is true for semi-hollow electrics, even though most tops, backs and sides in these instruments are laminates. A really nice jazz box with a carved or bent spruce top can suffer badly if dried out.

The finish of the instrument can also suffer due to lack of humidity. Old instruments using shellacs and french polish finishes such as European stringed instruments can develop finish cracks and even body cracks as they tend to be made from solid wood not plywoods. Instruments with a nitro cellulose lacquer finish can also suffer finish cracks because while nitro “breathes” it does not stretch and so as a body shrinks or swells, you will get ugly finish cracks. Nitro cellulose lacquer is also very sensitive to temperature changes and can develop what look like tiny cracks as a result. Polyurethane finishes do not breathe much at all and so do not age like lacquer and tend to handle shrinkage or swelling better. This is good from a finish perspective, but bad because you will not see the deleterious effects of drying until too late.

Steps to Follow

Get a humidification process in place appropriate to how you store and use your instruments. An instrument in a case is not how I work. I want to see them and play them at any time, so all are out. In winter I have a heavy duty humidifier installed on the forced air furnace to maintain humidity and use room humidifiers as necessary. In summer I use two room humidifiers in the main guitar room as it is quite large. Together they hold 18 litres of water and I have to refill every 2-3 days depending on how hard the AC is working. For acoustics I also use sound hole humidifiers that cover the soundhole completely. When I recently bought an Epiphone Hummingbird 12 String, it came with a really nice little soundhole humidifier, that had a very tight sponge in a tray, and a netting to prevent the loaded sponge from dripping into the guitar. I found many of the same thing under different names from China on Amazon and bought one for every guitar with a sound hole. Each one was about $20 CAD, less expensive than other humidifiers that I have tried and far more effective. In addition to providing humidification, they act as feedback reduction disks.

Thanks as always for reading and listening to The Podcast. Feel free to post comments or questions, I read and respond to all. I’m Ross Chevalier and until next time, peace.