When 50% relative humidity is bad...
 

With all the talk on the AGF about humidity, wanted to share this with everyone. I live in Guam where the outside humidity never drops below 75%. I keep all my instruments in an air conditioned room that maintains a temperature of 72 degrees and the drops the relative humidity down between 50-50%.

These are pictures of a guitar that I purchased on an international vacation trip in Asia. The top, back and sides are made of all solid mango wood. I don't know the temp and RH of which this guitar was built in, however, this is just to show that 50% RH isn't good for all woods. You can see the concave dip of the side right as the lower bout forms below the waist. This inward descending of the sides was much worse as this picture was take after I took it out of the room and set it in my living room at 74% RH for 8 hours.

http://farm3.staticflickr.com/2816/1...2ca93d3060.jpg http://farm3.staticflickr.com/2855/1...73813ceff8.jpg

I've had it in 74% RH for the past 24 hours and it's slowly straightening out. Just glad I caught it before it formed a crack.

There are Vietnamese-made mandolins (can't recall the builder offhand, but we have one we got at a garage sale) that are often extremely pretty, and not bad instruments at all considering their very low prices (no, they don't have fine luthier attention to detail, but they are still pretty). But when people in the U.S buy them they tend to crack like you wouldn't believe. I suspect though that if they stayed in humid, tropical, southeast Asia they would be fine!

Like I said, the one we have is actually gorgeous (though some of these instruments have over-the-top, excessive inlay), has a lot of volume (and has sound ports on the side, and some sort of double-walled sides), and is quite decent to play (especially seeing as we paid only about $25 for it! - new it was more of course, but it was never even close to being expensive). Compared to some of the junky mandolin shaped objects I've seen sold for similarly low prices, this is actually quite a wonderful instrument. But it has multiple huge cracks in both the top and the back. It seems stable and playable though, despite cracks you can practically see through, and I think there would probably be no point in repairing it unless we could keep it in tropical humidity all the time.

When 50% relative humidity is bad...
 

I understand what your saying. Fortunately, I live in Guam and this is actually a huge convenience for me. This guitar has a thinner depth than my Taylor 700 series but has enormous low end, it's actually quite unbelievable for mango wood. I play solo island music gigs looping with an uke and are often either poolside or beach side, so humidity is sky rocketed. Best of all, I can safely leave a guitar in our living room where wrongly run the AC when were lounging there.

Could it be that solid body electrics are the way to go in the realm of the golden dragon...? Good thing you caught it time! I've been to Guam -- it's ... warm.

Wondering…..could it possibly be that the woods used in building of the instrument were not properly aged and dried before final construction? And like you pondered, perhaps they store their wood stash at a much higher RH than does say Taylor.

I have no knowledge of that type of wood as a tone wood, its characteristics, etc. Sure is a beautifully figured and grained wood. Just thinking out loud.

I'm sorry, I don't see anything in those photos that would strike me as wrong? Where the binding and the top wood meet, it looks kinda bad, but I'm not sure that's what you're describing?

There's a big "divot" in the side of the guitar on the first picture. Pretty severe, actually.

It's not the level of humdiity, but the amount of change that is bad. Obviously, these instruments were made in a high-humidity environment, and even the conditioning of the wood was done at that same level.

your thread should be called "when living in Guam is bad". ;)

I'm not an expert in these things, but I'm quite sure this is exactly the case.

This raises an interesting question though....

If a guitar is to be used in a very humid climate, should the wood actually be dried to as low of a moisture content as guitar builders in the U.S. would want?

I'm not an expert either, but I would think the answer to your question is no. A guitar built in the U.S. under relatively low RH conditions (say 40-50% range) that then gets used in high humidity conditions usually sounds muddy due to moisture absorption. For a guitar intended to be used in relatively high RH conditions, I would think it would make sense to build it with those conditions in mind and voice it accordingly.

Regarding the OP, I think the issue is not so much that 50% RH isn't good for all woods so much as it has to do with the conditions under which the woods were stored and then made into a guitar. For instance, guitars made in Vietnam are often made of woods that were stored using no humidity control at all, and then built into a guitar also using no humidity control.

That means the woods would have equalized with the surrounding RH of the environment. These guitars are notorious for drying out and cracking when shipped to the U.S., no matter what woods were used in the build. That happens I think because humidity levels are generally lower here than in Vietnam.

Hope that makes sense.

D.

Couldn't agree with you more! In my OP, I mentioned I don't know the temp and RH of which this guitar was built in. So if it was built in a high RH like 75% in Asia, then like you said, the wood would have normalized to this humidity before when it was constructed. Taking this guitar to an RH of 50% would cause the wood to shrink...hence an instance for which 50% RH is no bueno.

I've had the guitar in my living room at 75% RH since posting this thread and it has leveled out, but not completely. I wonder how long it will take for the wood to return to its original state, we'll see. But having a guitar that can be kept in an RH above 70% is a huge convenience here in Guam.

So I've had the guitar in 75% RH since I started this thread, here is how it looks now:

http://farm3.staticflickr.com/2866/1...9346161d69.jpg

Back to normal. This guitar stays in the living room and is now used for all my pool or beachside gigs!

Beautiful looking top. So, is that mango wood, and how does it sound?

When 50% RH is not so good...
 

Joe, that is one very beeeeautiful guitar! I have a uke made with all solid spalted mango and it was love at first sight!

I know that I've seen a huge number of Chinese made guitars that develop cracks on either side of the bridge. It must be the change in the humidity that causes that, however, I don't know the RH in China, so it could be something else.

I don't own any, but I had heard that guitars made in Vietnam have a tendency to crack from the climate change. I assume this is because the wood has been acclimated to the high level of humidity in that country, and when exported to a country which has a lower humidity, the wood begins to shrink, and eventually crack.

I have several imported guitars from asia, from Japan, China, Taiwan and as far south as Indonesia, but I have never experienced an surface checks or cracks on any of them. I keep them at 60% RH in summer and 40-45% during the dry winter season. So far, it's not been a major problem, even though I have noticed a few tops that are slightly dipped. Maybe it's a good time to spring for a room humidifier. ;)

Glen