When you are starting out with your ukulele you may find references to humidity and how it can affect your uke. What do you need to know?
Humidity in the atmosphere can have the effect of causing serious damage to a ukulele. It should be born in mind that this issue mainly affects solid wood instruments. Wood is a natural material and it changes by expanding and contracting as it takes on or loses moisture from the air around it.
Lose moisture and there is a risk of the fingerboard shrinking, the instrument cracking or distorting if left unchecked for too long a period of time. Too much humidity and you can find the top of the instrument swelling and similar distortions. At best this can cause cosmetic issues with the ukulele (such as small cracks in the finish or the wood itself), but at worst can throw the instrument permanently out.
Before you start to panic though, the requirement to keep a check on humidity only applies to those of you with instruments in locations with humidity at either extreme (those in the far east, or Arizona, take note)
The best humidity for a wooden instrument is between 45% and 55%. If you have a humidity gauge in your home and are regularly falling way below or above this level you should think about your options.
In a dry climate, you may want to consider investing in a humidifier – this is a small device that lives in the ukulele case, or hangs inside the sound hole that contains a sponge material that holds water. The water is then given off through evaporation and keeps the instrument in a more humid atmosphere. Ensure you purchase a product designed for the ukulele as you need to ensure it maintains that ideal humidity level. I stress that this is only required in a dry environment, and if your uke doesn't need moisture, forcing humid air onto it can damage the instrument.
If you live in a very humid country, then your problem is tougher to solve and you may need to consider a de-humidifier for the room your ukulele is kept in. A tightly sealed case may help, but keep a close eye on the instrument.
For those who live in more stable climates, be aware that you can create your own problems too - never leave a ukulele next to a radiator or heater, in direct sunlight or in a hot car! Houses with central heating that runs like a steam train and keeps a house hot hot hot, may also create dry environments, and you may want to think about a humidifier.
Humidity gauges are cheap and easily found online - if you think you may have an issue with your local environment I would urge you to buy one and consider your options.