Humidity, Guitars, Truth and Prevention
Posted on December 20 2016
It happens every winter in the repair shop, customers come by with guitars complaining about a little buzz or bad action. Turns out it doesn't just need a setup. Keeping your prized possession on a stand next to a heat register may not have been the best idea. When a guitar gets dried out, it can often be reversed, most of the time without any severe damage. This may take a couple weeks or sometimes even a couple of months. Unfortunately we're not always so lucky and guitars may need major repairs, which in some cases could out-value the instrument altogether. Prevention is simple and inexpensive so let's discuss how to keep your guitar stable through the dry winter months.
What is Relative Humidity?
Relative humidity is exactly that, relative. It is the amount of moisture the air can hold at a given temperature. So temperature has an affect on relative humidity. Warmer the air, the more moisture it can hold, so the more moisture required to achieve 50% relative humidity. Guitars are most comfortable at around 50% relative humidity. Some people say 48%, some say 52% but let's keep it simple, 45-50% is great.
Coming to Terms with the Truth
If you think that your house in the dead of winter is 50% humidity in the northeast, you're wrong. It's not 50%, it's not 45%, it's not 40%, it's probably less than 30%. If you think I'm wrong, buy a humidity gauge. Buy it from us or buy it from anywhere else. Take a picture of your house's humidity at a correct 50% and we'll reimburse you for the gauge. That is, of course, if you don't already humidify your house.
What's the Big Deal?
Your acoustic guitar is not finished on the inside. So moisture can come and go as it pleases with no resistance from the inside of the box. The top of your acoustic guitar holds about 1-1.5 oz of water at proper humidity. So when it gets dried out it actually shrinks. The top can get sucked in and form ripples. When the top sinks, the action can get so low that the strings just lay across the frets. The carefully fit glue joints can come loose. The bottom of your bridge has a radius to match your top when the guitar is in proper shape. If the top shrinks, your glue joint is compromised and the bridge can lift. The same holds true for braces and even the joints where the sides meet the top or back. If the glue joints don't come loose that's when something else has to give. This is where humidity cracks come from. Something has to give when the guitar gets dried out, and if it's not a glue joint it's going to be the wood itself. Often it's both.
Quenching Thirst and the Mass to Moisture Ratio
On a recent trip to Taylor Guitars in El Cajon, California, we learned some new information that changed the way we discuss guitar humidification. Taylor painstakingly maintains a 50% humidity throughout the factory with a herd of steam breathing robots. They even have a room where customer-owned victims of humidity damage can rest and recuperate to prepare for any number of routine surgeries. However, Taylor was having a problem years ago where customer repaired guitars were developing issues upon return. Properly humidified, carefully repaired and returned to their loving homes only to develop humidity issues soon after. The culprit, as it turned, out was a room at the factory that was not humidified where the service department was storing customer cases while the guitars came back to life in the sauna. The danger was in the details: the average guitar holds 200 grams of moisture at proper humidity while the average case holds 500 grams of water. So if you put the humidified guitar in the dry case (and that dry case has more than twice the mass of the guitar), your case is going to take a big old drink from your guitar and put you right back to square one. So Taylor was able to solve the issue by keeping the cases open in the sauna with the recovering guitars. Another lesson learned, knowledge is power and the moral of the story : The bigger box gets to drink first.
Preventing Humidity Damage
Preventing humidity damage is a simple assembly of a few giant puzzle pieces. The first piece is knowledge. You learned above the how's and why's of guitar humidity. The second piece is awareness. You should buy a humidistat and learn the truth about your home and it's actual moisture level. The numbers on your humidifier or dehumidifier are not accurate, they are very rough approximations. Taylor makes a great humidistat that we use around the shop. Once you have a realistic snapshot of the true climate in your home you can decide what systems and practices work best for you. The third piece is commitment. You need to commit to maintaining your guitar through the seasons to protect your investment and guarantee that it turns into tomorrow's vintage instead of tomorrow's wall art.
Our Winter-time Recommendation:
We like to pair two systems together to guarantee success. The D'Addario Two-Way Humidity System (formerly Humidipak) is a foolproof way to maintain your guitar and case at around 48% which is perfect. The system is bi-directional and will push out and pull in moisture as needed to regulate until the packs burn out. Packs can last anywhere from 2-6 months in our experience. We like to couple this system with the Oasis Case Humidifier. It mounts inside the case and holds 32 grams of water when it's full. It acts as a reservoir for your Two-Way System and extends pack life. Keep that little guy full and you could get through the winter on one set of packs.