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Hi all,

Thanks for all the kind help I've recieved on this forum so far, much appreciated.

I'm renting a house which had a large shed which was half rotten.I've rebuilt it but it has no moisture seal and getting the humidity below 60 % appears to be impossible. I've heard of drying wood in a box prior to gluing.how might you go about doing this or are there better ways?

Thanks, Mike.

I have a dehimidifier but it really struggles to drop the shop humidity by anything more than 8% RH. I've sealed as much as I can and I don't have the option of turning it into a smaller space. I would need an industrial sized dehumidifier to obtain much greater control. Then there's the noise and the electron bill. I no longer use my dehumidifier and have switched to the much greener option of using my UV light box. It's become a multi use facility as wood tanning, varnish drying and humidity control.
You need something the size of a single wardrobe/cupboard, anything that a whole Guitar can fit into. Place a light fitting bulb at the bottom. Then it's just a matter of determining the wattage of the bulb required to drop the humidity. The higher the wattage (heat) the lower the humidity will be. You can control things further by incorporating vents that can be both opened or closed. As a very rough guide a 40 Watt bulb can drop the humidity by 30% in a fairly well sealed cabinet. You will also need to watch that the temperature doesn't climb too high (unlikely) and make sure it's safe in respect of fire and electrical shock. One of those small very low wattage tubular heaters are probably safer.
You will need to 'condition' the wood in the correct humidity for a certain period of time. Thin wood, as in Soundboards or Backs react pretty quickly to humidity changes. I can have an unbraced Top go from distinctly convex to distinctly concave in a couple of hours or less. Thicker wood will require much longer. So if I'm gluing a fretboard onto a Guitar I'll place both the Guitar and the fretboard inside the cabinet, probably for 8 hours or so (due to the thickness of the fretboard). It's all removed from the cabinet and then glued up. I don't bother putting it back in the cabinet whilst the clamps are on.
Gluing braces on to soundboards, braces on to Backs, Bridges, Fretboards and assembly of the box are the important and necessary procedures in a humidity controlled environment.
BTW for the last 4 or 5 weeks I've been seeing RH of 70% + in my shop. Pretty unusual for this time of year. Normally I see a window of opportunity when the humidity drops below 50% RH for one or two weeks out of that period. Of course there are always local variations and differences to indoor and outdoor humidity, even variations from one room to another.

Thanks.this is what I wanted to hear.just to verify, you dry tips backs and bracing in the cupboard and take them out to glue and then leave them out, glued and clamped amd dint worry about returning them to the cupboard?

Yes, although everything is prepared beforehand in terms of clamping. When I take things out of the box everything is ready for gluing immediately. I also use HHG so quite often the clamps can be removed after an hour or so.
If I had a much larger box I might return everything to that box but I haven't found it to be an issue. I only use the box for humidity control a few times per year. Mostly I can glue things when the humidity happens to be in the right area and work on other things when it isn't. There's always some solution or working method that you can adopt. It just takes forward planning but the box is a simple and efficient method for controlling humidity.

I use a dehumidifier in a closet. I lined the closet with plastic sheeting and semi- sealed the door. This makes things manageable for the small dehumidifier and keeps the power usage reasonable. During the cooler months I use a small oil filled space heater to raise the temperature (which lowers the RH) in the closet. I like to return the parts to the closet after working on them to allow the glue to cure under favorable humidity conditions. I only control the humidity when necessary.
Some people will wall off a part of their shop with plastic sheeting and humidity control only that work area. Others may carry the parts from the unheated shop to the climate controlled house. Waiting until conditions are favorable is also an option. What works for an amateur may not for a full time builder.

Think of the millions of guitars built in uncontrolled shops.
For years (before the internet!) I only built for the local area, and I did not have humidity control, and I live in a humid area.
I had very few issues with these guitars, maybe a top or back crack over 20 years, and I was glad to repair them, and to see them again.
Arched bracing was my friend.

If you want to send your guitars out into the world, disregard this advice.

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Some sources I've read suggested that makers would warm their parts over a heat source before doing glue ups. This would dry thin plates as well as give a little more open time when using hide glue.

Presumably, it also made them look a little bigger at toilet time.

I beg your pardon?

Clay was discussing makers warming their parts over a heat source.

Oh well, I still don't get it. Maybe I shouldn't?


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I think the opposite would be something like this:


Alex


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Informed and amused.Thanks forum.

Do we really need potty humor on this forum?

Interesting -- Jerry Seinfeld, became one of the wealthiest people on the planet appealing to millions because he understands the humor in being a human being. I think the members of this forum can handle a little off color adult humor. Gads zooks find a thread that does not zoom wildly off topic.

Jerry Seinfeld never appealed to me and neither does his wealth...come to think of it, what appeals to millions, usually does not appeal to me...
Zooming wildly off topic has nothing to do with garbage. This forum is supposed to be about building instruments, not who can make the kutest (with a K) wise?crack...or is it? Maybe we should all yuk it up till the football game comes on?
Think of the women and young folks looking at this. What does it have to do with humidity control?
End of "off topic", I hope...

Thanks David for this, very sound reasoning with particular emphasis on your last statement. If there is a chance that one will be selling guitars proper RH control is a must. There are very good reasons why Martin, Taylor, and even many smaller shops have spent likely millions on environmental controls. The ROI is reduced warranty claims, less liability AND most importantly greater likelihood of very happy clients!

Never was a fan of keeping work in progress in a little box and instead my home shop was built with RH control in mind with insulation, vapor barriers, and a semi-sealed environment. In the winter I need just a tad of humidification and in the summer a bit of dehumidification and all is well.

I suspect that in other climates one could get by with less control over the RH of their shop but here in Michigan, crack city in the winter..., RH control is as important to guitar building as golf clubs are to golfing...

The perfect environment…the perfect tools…the perfect wood? I believe that if we wait for all the stars to align and material and environment are just right, not one single guitar would ever be built.

I build with the wood I can afford in an environment that keeps the rain off me.

I think I’m turning into Grumpy! BTW, whatever happened to Grumpy? If he doesn’t show up, I’m going to take his place!

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Tony Flippo

I think the threads we have had here with titles like "my back has cracked" "my top/back has sunken" say enough about the need for humidity control

Relative humidity varies from hour to hour throughout an average day, as well as day to day and seasonally. The difference between a heated or air conditioned environment and the ambient outside humidity can vary by 50 percentage points or more. Even if your instruments are used locally it is still prudent to build at a humidity level that allows for the greatest degree of relative humidity change.

The title of my thread is maybe a little misleading.i was not meaning to build without any consideration of humidity, it's just that it is not possible to control the whole workshop environment.

These threads always wander a bit, but hopefully you did find some useful information on your intended topic. There have been several opinions and methods offered on the level of humidity control needed to build a structurally successful guitar. Sort through them and use those that make sense to you and fit your particular situation. And remember - warm your parts to avoid shrinkage issues.

I just have a small uninsulated garden shed and around this time of the year the RH is usually too high for any cross grain gluing. Fortunately there are always plenty of jigs and molds for future builds to be getting on with til things are more suitable!

I read somewhere years ago that Martin used to hang their tops from the rafters high up where the air in the winter was driest and warmest before they were braced. Don;t know what they did in the summer.

Michael N - great post. Good idea, good explanation, good science.

Ed

Thanks everyone.bought a nice old mahogany cabinet, got my light bulb in, hovering around 42-43 percent. Little bit of a faff but it's working a treat. Can't for a whole guitar in but can fit body and neck separately and I'm using a bolt on so it's not really a problem. Thanks.