Reduce the moisture content on guitar top wood.

[nonameguitar]

Well, Im not a wood wood expert and don't have much knowledge about this issue. I hope the experienced luthiers here can help me.

I got one sinker redwood set that I plan to use on my guitar a few months ago. Very nice appearance and good tap tone. There are some mineral stains on the set like the one used on Taylor. I'm in the country that have relatively high humidity now and the access to guitar tone wood is quite limited. The set was sent oversea to me.

The problem is the moisture content of the set I got is always around 20% since the first day i got it. My luthier told me that it should be around 8% to make a guitar. We left it for about a month and nothing change.

Therefore, we put the set in the sealed foam box with silica gel for about 2 weeks. After that, the moisture content seem to temporary reduced to 10%. However, when we remove the set and are about to start building, the moisture content went back to 20% again.

I know it's my mistake to get the wood with high moisture in the first place. Try to minimize damage and make the set usable now.

Any advice to solve this problem? How to reduce the moisture in the top wood in my case? Using silica gel again but this time put them longer? Any other methods? I know the best way is to leave it and to let it be air-dried but I heard that it may take up to 1year or more. Cant wait that long too.

The wood looks really nice and would be awesome on my guitar. If possible, really don't want to find a new one as a replacement (some budgets concern too)

Thanks in advance.

[runamuck]

A guitar really needs to be built in an environment where the humidity can be controlled. In your case you'd need to use a dehumidifier for that to get the relative humidity down to around 45% in your shop.

As your luthier friend has said, building at 20% moisture content in the wood itself, will lead to big problems. I know some builders will bake their tops in an oven to reduce moisture content although I'm not sure that baking from 20% is a good idea. Perhaps someone with experience with this can add something here.

Jim McCarthy

[Tim McKnight]

^ Ditto what he said. Unless you have an accurately controlled temperature and humidity stable room to store the wood (AND BUILD THE INSTRUMENT IN) the wood will absorb moisture from the atmosphere and the moisture content will equalize with your surrounds as you have discovered.

Your builder is correct, build with wood that is stable, and has been stable at 6%-8% MC or suffer the consequences. Let your builder resource and store the wood if you want a stable guitar at the end of the project.

[Bruce Sexauer]

It sound like your local humidity is much higher than mine. If your wood is self adjusting to "20%" then it is likely that's natural. But the question then is, is it like that all year where you are? If it is, and you are going to be using the guitar in that environment, then there is no reason not to build the guitar at "20%". In fact, there is every reason why you should. A guitar is best built at a relative humidity similar to the one it will be used in.

When I lived in the Pacific Northwest the humidity was not ideal year round for building guitars. No one I was aware of at the time was controlling humidity, instead we simply took that part of the year off and did something else.

Luthiers build in humidity controlled environment (if they do, I don't) because they are going to be sending their work to environments other than the one where they work.

[Kent Chasson]

Pan, do a search for Equilibrium Moisture Content (EMC) in wood. Sounds to me like your wood is reaching EMC at 20% which would happen in a place like Singapore where the year-round humidity is 80 - 90%.

If you build a guitar with wood at 8% MC and you live in a place where the humidity is in the 80's - 90's, the plates will expand, the top will have a huge belly, the action will rise dramatically, and the sound will likely suffer.

But if you build with wood with a high moisture content and take it to a drier place, you will likely get cracks.

If your humidity is indeed that high year round, I'd split the difference and build wetter than normal but below 20%.

[nonameguitar]

Thanks a lot for inputs.


The humidity in my city today is 79%. I believe yearly average is around 73%. Average temp is around 83F.

Forgive my lack of my knowledge, ( and English is not my main language)

A lot of woods (i think most or all) using by my builder have MC remains below 10%. (Including the back and sides I plan to use) I think he built a lot of guitars with MC around that and from what I hear, there is no problem regarding this issue. From what I know, we also lack a method to build in completely or well controlled environment.

The reason we concern is that this specific top wood has 20% mc which is really hi. We try to reduce it but it changed back to 20%. If that is its natural EMC, I wonder why other sets didn't self-adjust like this one.

No matter what, MC 20% seems really too high. I use a calculator from a website I found (not sure about its accuracy) by entering average temperature and humidity, the EMC should be below 14%.

Therefore, should I try to reduce its MC or change its EMC if possible? Then, how? Bake it or put silica gel on it again? The wood need time until its EMC change? (to really match tempt and humidity)


Thanks again.

[dekutree64]

Originally Posted by Kent Chasson

If you build a guitar with wood at 8% MC and you live in a place where the humidity is in the 80's - 90's, the plates will expand, the top will have a huge belly, the action will rise dramatically, and the sound will likely suffer.

On the bright side, redwood is one of the best to minimize this problem. Its dimensional change for a given RH change is a lot smaller than spruce, so it won't swell up too badly.

Just get the wood into the luthier's shop (with both sides exposed to air) and wait a couple days and it should be acclimated to whatever humidity is in there.

[Atkin Guitars]

Thought you may be interested in this.

Originally Posted by runamuck

A guitar really needs to be built in an environment where the humidity can be controlled. In your case you'd need to use a dehumidifier for that to get the relative humidity down to around 45% in your shop.

As your luthier friend has said, building at 20% moisture content in the wood itself, will lead to big problems. I know some builders will bake their tops in an oven to reduce moisture content although I'm not sure that baking from 20% is a good idea. Perhaps someone with experience with this can add something here.

Jim McCarthy