Official Luthiers Forum!

I am a newbee and am a little confused about summer humidity issues. What are the acceptable ranges for building? Can a air conditioner and dehumifier lower it enough in the summer or do you guys just take the summer off. Guess it also depends on the climate I live in New York State.

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Mistakes are mandatory-learning from them is optional. http://www.opensourceluthiersupply.com

An AC unit and a dehumidifier should be fine in NY state, if the shop is fairly well insulated. I remember summer days in NYC with 90% humidity…
Between 40% and 50% is the modus vivendi for building guitars.
Personally I prefer to glue braces and assemble the body on the dry side, as low as 30%, as I feel the top and back retain more of their original radius this way.

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

It depends on whether you are building in a drafty barn or a tightly constructed and sealed modern building. If the latter, then you should be fine with an AC and dehumidifier if they are properly sized to your space. I had to do some serious work on my 2-car garage to get it sealed from the gulf coast humidity before I could start building in it.

What the others have said.

In addition - understand that even with AC the dehumidifier will produce a good deal of heat. In my former 11' X 11' shop on a hot day with the AC on the shop was 75F. When I turned on the dehumidifier and reached 45RH the shop was now 83F.........

Boxer shorts, though optional, come in handy on hot summer days....... Just be careful around your thickness sander..... and never leave a hot bending pipe clamped overhanging your bench..........

I can understand the hot bending iron but I won't have a problem with the thickness sander.....lol.....ha ha.......standard whiteboy issue

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"After forty-nine years of violin building, I have decided that the search for a varnish is similar to the fox hunt. The fun is in the hunt."
Jack Batts Maker and Repairer of Fine Violins

Barry,

What steps did you take to seal the garage off and deal with the humidity. I’m in North Florida and can feel the humidity starting to really build up. My plan/folly has been to work in the garage when I need to and bring everything inside when I am done. However, I have not yet pulled off an acceptable (approved) work location indoors. I’m concerned about the garage humidity. But if I can cut back on it……

John

The two biggest problems with humidity control are air exchange and concrete. You can get a blower door test to find out what your air exchange rate is, and where the big leaks are. Garage doors are notorious, of course.....

Concrete is just about transparent to humidity. A good sealer coat should help with that. I acutally laid down PT 2x4s on a two by four foot grid on the concrete floor in my shop, put plastic insulation in the spaces, laid down a vapor barrier, and finished off with two layers of plywood and vinyl tile. I now have a flat, smooth floor that does not pass water vapor and is reasonably comfortable underfoot.

Many people build a simple plastic tent inside the shop, over the main work bench, and seal it off well. It's relatively easy to control the humidity in that small space, and the DH doesn't gobble as many amps to heat the air with.

In my shop, which I spent a fair amount of time sealing up (and still have some more to do), I only use the DH in the spring and fall, when the humidity is up but the weather is cool. Once the air conditioner goes into service it removes enough humidity to obviate the need for a DH. A smaller AC unit will run more, and remove more humidity than one that is 'properly sized' for the space.

... and in addition, there are a lot of things that can be done in a high humidity condition. I let my shop cycle through the high low conditions and most of my wood is in there. I am more of a violin maker though. But when I perform any operation that requires low RH, I crank up the dehumidifier and my shop responds very quickly. A couple of days and all of the wood I am using is at equilibrium and I feel comfortable performing cross gluing operations. This would not be practical for a lot of professionals, I realize. But it is an option for the part timer and weekender. Fingerboards can be a problem though and I like to keep them at low RH as much as possible.

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Ken

Here is the deal. There is no magic RH It is all about stability due to consistent RH range. You can build in a wide range of humidity as long as it is fairly constant. “Consistent” That is the key word to remember. If you live in an area where the RH is always 30% (few of use are so luck) then you need not do anything to control the RH as long as the instrument is going to stay in that region or a region that has a similar climate The 45-50% RH come from the fact the this is the medium world wide RH. This gives the instrument a fighting chance to acclimate to any location when properly cared for.

That said if the instrument was build in lets say 60% RH and was shipped to a location with 20% RH, the instrument would loose a lot of moisture and cracking and joint separation due to shrinkage could accrue. Reverse that to where the instrument is built in 20% RH and shipped to 60% RH, there is far less risk of damage but swelling is a possibility. Hardwoods expand a shrink at a far lower rate than softwoods. So tops are always the first problem to show up. So you see it not about a perfect RH for the wood. It is about a relatively constant RH for the wood in relationship to the structure of the instrument

I live in an area of the country that I have to add moisture year round to reach 45% rather than extract moisture, even in the summer. I keep my shop between 35%-40%