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OK, I have been doing a much better job of monitoring the relative humidity in my shop in recent times, thanks to this forum. I have a more reliable hygrometer (Abbeon), and I calibrated it pretty well. I am sure I could do more, and I plan to in the future, but right now, I think I have a good rough idea of the RH in my shop.

I am in the midst of building a pair of guitars, and I am at the point where I should start bracing soon. While my dehumidifier is working hard, the recent rains in my area have driven the RH up pretty high. The lowest I can get in my shop right now is in the low 50s, like around 52-54%. The RH without my dehumidifier running would be over 60%.

I have some other things I can get done while I am waiting for the RH to go down, but I will run out of those other tasks soon, and I would rather not wait until the fall to brace the plates and glue the bodies together.

My questions are twofold:

1. Am I courting disaster by bracing and gluing the bodies together with RH in the low 50s? These guitars will have to survive winters where the RH gets down into the high 20s, even with help from humidifiers.

2. If I need to not glue up with RH in the 50s, how successful have others been at the whole "dry room" thing? I do have a separate machine room in my shop, and I could store all of the wood in there with the dehumidifier going just in that room, and probably get the RH down into the low 40s without too much trouble. However, I need to work on the guitars in a different room with high RH. Can I successfully store the wood in the dry room, work on it in the sloppy wet RH workspace, then let the glue dry in the dry room?

Thanks in advance for the advice.

1) asking for trouble for sure I feel. I glue at 40%.

2) that's what I have, it's the machine rooms and bending area left to swing. Why not take your go bar deck into the machine room for the job if you can get it to a lower RH? Get it down for a few days with the tops and backs and braces braces in it, then do your glue ups...

Yep, either wait until winter, or dry them out before gluing. I sometimes use the oven, or just leave them in a sunny window for a few hours with a wood hygrometer to monitor, which should respond at a similar rate to the guitar plates.

I prefer 30-35% for bracing.

I had the opposite problem, wanted to glue up in the teens or low 20's (really). I enclosed a bench with poly film, stuck a fan in there blowing on a plate of water. Put the wood in there for a couple of weeks and when I was not building with it. You could do the same but to lower humidity with a box and a light bulb in it. The RH will drop and when the wood is acclimatized time to glue up.

Wow I didn't even know it was possible for the humidity to go so low! Here in the UK it very rarely goes below 40/50% outside even in the summer. It's often up in the 90's in winter.
Can you import some of your weather over here?

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That low RH in the winter I mentioned is due to extreme cold outside, heated air inside, and the absence of a humidifier (or a strong enough humidifier) to add enough moisture to the heated air. There are times when our outside temperatures are in the teens or below.

It can get to -40 here, not much moisture in the air when it comes inside. Used to spend time with a girl from Bristol. She showed people pictures of trucks on the river where people were ice fishing.



The river in spring. The same area as above but looking towards the bridge. The chain link fence is the same one in both pictures.

It's currently over 70% in my basement space. I'm carving necks, cutting pearl for inlays, building jigs, working on a buddy's Japanese surf inspired electric build. Fretting a richlite fingerboard.
Not much else to do but wait. I have plenty to keep me busy for now.

Forget the outside, outside isn't relevant. RH, generally speaking, is higher in summer, lower in winter. I can't ever remember readings going much below 40% RH in summer but I've certainly seen it in the mid/high 20's in the winter. Not often but it does happen.
I see that the recommended glue up humidity level is slowly creeping ever downwards. It used to be 50%, now it's nearing more like 40%. In another 10 years we might be down to 30%.

When I built my shop, I used plenty of insulation in the floor, walls and ceiling. Also used heavy visqueen vapor barrier and drywall. The area is 12X12 that is kept temp and RH controlled. To get a handle on RH, I think that you have to prep the shop area first.

Question 1: It depends on where your guitar will reside once completed. Most Mexican guitars are made with no regard for humidity level. So long as the guitars stay in Mexico where humidity doesn't drop extremely low they hold up fine. When inexpensive Mexican guitars are brought into colder climes they are usually toast by the end of the first winter.

Question 2: A dry room is the best solution, IMO. A sealed room, perhaps 6'x8' with a good vapor barrier is very easy to get down to 40%-50% with a small dehumidifier. Brace your stabilized plates and close the box in the controlled room and carry out all the other operations like neck carving, fretting and binding in a room that is heated/cooled to your comfort level. About 75% of the operations in building a guitar are not at all humidity sensitive.
The humidistats built into dehumidifiers are pretty bogus. I set the dehumidifier control to "on" and plug it into this:
http://www.zoro.com/dayton-dehumidifier-control-plug-in-120-v-1uhg2/i/G3370446/
Just ignore the digital readout on the Dayton unit and rely on your Abbeon to set the "on-off" point.

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Stay with the happy people.
--Reynolds Large

I think I will just wait out the high humidity, if I can. Moving my gluing operation to the machine room is a fair amount of trouble. My dehumidifier is working well, but it is outgunned at the moment.

My main workbench is in an open floor plan area of my walkout basement. The machine room, in which I house all of the larger woodworking equipment, is not set up for hand work, and there is no room for squeezing something else in there.

I think I can stay busy with other things until the fall.

Out of curiosity, I guess I should have asked about working with a dry cabinet and a wet workshop, instead of a dry room. I can turn my machine room into a fairly large dry cabinet, but I really don't want to do a lot of hand work in there. Does anyone have comments about working with a dry cabinet in a wet shop? I will search the forum, obviously.

One interesting thing about the downward trend in preferred RH for gluing up the box: I looked at the opening sections of the Cumpiano book, and his "ideal" RH range is 40-55%. Is a drier gluing environment progress or overcompensation? Interesting question that probably depends on perspective. What is worse: excessive swelling in the summer because the box was glued up in 30% RH and it now lives in 60% RH or higher, or the risk of cracks in winter because the box was glued up in 60% RH and it now lives in 30% RH or lower?

In any event, thanks for all the feedback. I appreciate it.

Taylor braces and assembles guitars at 47% RH. Say what you want to about Taylor but they don't do anything by accident.

_________________
Stay with the happy people.
--Reynolds Large

I agree, but I will also note that in my shop I repair more cracked Taylors than most other brands combined. However, I blame the owners, not Taylor. Taylor has been at the forefront in educating guitar owners about the importance of hydrating their instruments.

I keep my shop at 45-50% year round. My shop is in a large 2.5 car garage and is not super sealed up, but is half underground. I have no problem maintaining correct humidity levels (as checked using a wet/dry bulb hygrometer) using a standard dehumidifier.

My personal approach is to educate my customers and then let them take responsibility. I do not warranty my guitars or my repair work for damage caused by dehydration.

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It will probably be alright.

Lockport Manitoba?

Yes.