Different woods vs. Humidity

As I finish gluing the bridge back on my KPK, I am left wondering about different solid woods and their vulnerability to humidity or lack thereof. I realize that laminates have the advantage here, but I would think that there is a variety of response to humidity between the main species of woods that are used: Mahogany, Koa, Acacia, Spruce, Maple, Cedar, Mango, etc.

I ask this because where I live it gets very dry in the winter and with a house humidifier and room humidifier running, the humidity never gets above 30% which, I heard somewhere, is not as high as most woods need to prevent cracking and shrinkage (this could very well be wrong info.) Since I like to leave my ukes out where I can play them, this precludes the use of an Oasis or other in-case humidifier. So am I left with laminates as my only option or should I just get really adept at uke repair? My hope is that there is at least one decent tonewood that can weather changes in environment well enough to consider an option. Any thoughts?

It's very dry in the winter where I live as well. If you have good quality, hard cases for your better ukuleles, I recommend that you store the ukes in their cases with humidifiers. I use Oasis sound hole humidifiers and add some homemade ones for larger instruments. I also have in-case hygrometers in a few cases so I can monitor the RH in the case. Generally speaking, you should try to keep the RH at about 50%.

I think that while there may be some variation regarding different species of wood and their reaction to low RH, but, the ill effects have more to do with the RH where and when the ukulele was built.

campfly said:

As I finish gluing the bridge back on my KPK, I am left wondering about different solid woods and their vulnerability to humidity or lack thereof. I realize that laminates have the advantage here, but I would think that there is a variety of response to humidity between the main species of woods that are used: Mahogany, Koa, Acacia, Spruce, Maple, Cedar, Mango, etc.

I ask this because where I live it gets very dry in the winter and with a house humidifier and room humidifier running, the humidity never gets above 30% which, I heard somewhere, is not as high as most woods need to prevent cracking and shrinkage (this could very well be wrong info.) Since I like to leave my ukes out where I can play them, this precludes the use of an Oasis or other in-case humidifier. So am I left with laminates as my only option or should I just get really adept at uke repair? My hope is that there is at least one decent tonewood that can weather changes in environment well enough to consider an option. Any thoughts?

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Since the bridge is the issue you talk about, use a better glue to hold the bridge on. As far as humidity is concerned, all woods will react if the humidity gets too high or low. and that includes laminates. Solid woods may suffer from cracks over time but laminates can also suffer from de-lamination, especially the
cheaper ukes.

If the uke is built with woods that are properly cured before they are used, built in a shop that has the right levels of humidity (42-50%) they will weather well if cared for. Living in a place where the humidity level is never higher than 30% is problematic for any wooden instrument. No decent tonewood is going to do well over time at those levels. Maybe you should consider a graphite body?

Thanks for the replies. It looks as though I might have to "Winter" my ukes in hard cases with humidifiers and then get them out in the Spring. Sad thought.

Regardless of my personal dilemma and the good suggestions that you've made to solve it, I would imagine that there are still differences between various species and their vulnerability to the environment they're in. If they transmit sound differently, then it stands to reason that they would transmit air and moisture differently as well. But that may be a very naive assumption on my part. I am still interested to learn more about these woods and their qualities if anybody has any info to share.

BTW, I am not sure that dry air was necessarily the culprit in my bridge coming unglued, but it just got me thinking.

I see no need to pack your ukes away for the winter and not play them. Just keep them in cases during the winter months when not playing them and take them out when you want to play them (I mean, don't let 2~3 latches stop you from playing your ukes). Where I live it's usually around 25~30% humidity during the winter months indoors. When I want to play a certain uke, I take it out of the case and either play it or leave it on a stand or couch. The uke is usually out of the its case for 4~6 hours and I've never had a problem with any solid wood ukes I've treated this way.

I did have a couple of ukes with wood movement issues that required repair, but those occurred because I didn't properly hydrate the case and those two ukes were more delicate to begin with (Koa Works a week after returning to MN with me from Hawaii, and Glyph without in-case humidifier filled for extended period of time). I've gotten lazy on filling the in-case humidifiers on many ukes (it's a PITA to fill humidifiers for 15 ukes ), but other than the two I've noted, the rest have been just fine even when I've slacked off on hydrating them in the winter.

I've always left a guitar or two out all year around wherever I've lived and I've lived in a lot of places. Here in Miami I mostly deal with too much humidity so I try to keep the guitar/uke I leave out near an A/C vent. When I lived up North in Baltimore, I kept a room humidifier going nearby during the winter. Sometimes in different areas the humidity is better in relationship to the humidifier. Also, if your humidity is still low, you can try getting a better humidifier. I have one that can bring a 11'X16' room to 70% humidity during winter in Long Island. I've tried a few different ones, and found that a lot of the cheap ones that go for around $40 or so just don't do the trick. I used to have the Pure Guardian H4500 and it really made a huge difference although it cost around $100.

As GX9901 said above, you don't have to pack your ukuleles away during the winter. Just keep them humidified in their cases when you're not playing them. It takes a while for them to dry out such that it causes problems.

I really don't think that trying to assess how different species of wood are variously impacted by humidity is going to serve any purpose for you. Were you to discover, for instance, that koa is more prone to crack than mahogany, what would that do for you. In other words, mahogany will crack if it gets too try as well. Like I wrote before, the tendency to crack is influenced by the RH of the shop in which the ukulele was built,i.e., the moisture content when it was glued up. Many shops try to maintain approx. 50% RH for this reason.

To answer your question specifically, yes different woods expand and contract by varying degrees due to changes in relative humidity. The most stable wood in this regard is Port Orford cedar, followed by its close relative Alaska yellow cedar. Both are excellent tone woods and should be considered by people living in areas of large humidity swings.

Brad