Humidity

[tjp]

So I moved a couple months ago, and am finally getting around to setting up to build. First commission! Gotta love those deposits...the winter weather on the north coast of CA, not so much.

Anyhow, what range of humidity do y'all consider acceptable for building? As of last night, it was 70% in the shop (unheated detached garage), in the house, humidity was mid-50's. I have the top and back hanging out in the house near the woodstove for now, thinking I can do humidity-sensitive work out in the shop during the day, when it is warmer and humidity is lower, bringing pieces into the house to store it.

[redir]

Do you have any means of controlling and accurately measuring the RH? You can move stuff around like that as you said but it's risky. Some people will build storage boxes with source of humidity control for overnight storage. 40-45% RH is generally what we go for when building. My shop is kept at 40-45% 24/7 year round and I store the majority of my sets and tops in that same environment too so that they can be used right away. Thin plates react fast to changes in RH. You really do need to be very careful with it.

[tjp]

Thanks for the reference point. I've thought about a humidity controlled box in the garage. Would not be that expensive and could potentially save a lot of heartache...

[Shuksan]

IMO, if you are going to be building guitars for paying customers, then you need to building under controlled humidity conditions, at a bare minimum when gluing braces to the top and back. Otherwise you are risking an unhappy customer coming back to you with a cracked top and/or back. If you are building at humidity levels above the range of 40-45% redir mentioned above (which is what most builders aim for), this will be a substantial risk especially if the guitar owner lives in or moves to a location with a significantly drier environment than the north coast of CA.

The humidity of a garage-size shop can be easily lowered from the 60-70% range to the ideal building range with a small dehumidifier. A humidifier that is adequate for the job can be had for under $200. Pretty cheap insurance.

[tjp]

Thanks Shuksan, will look into that too. I assumed it would be much more expensive than that. Summer conditions are pretty close to ideal around here. It's the pesky winter drizzle that gives us fits.

FWIW, 10 guitars in, no cracks. But I want to keep it that way.

[Carey]

Hoping not to go too far away from the OP's query, but does anyone have a
strong recommendation for a not-expensive dehumidifier for a ~14 foot
square room? Not too noisy would be nice, too...

[charles Tauber]

Originally Posted by Carey

Hoping not to go too far away from the OP's query, but does anyone have a
strong recommendation for a not-expensive dehumidifier for a ~14 foot
square room? Not too noisy would be nice, too...

Mine are old and they don't make those styles/brands anymore. Most of the recent ones I've seen have very small collection tanks, so that they don't hold much before needing to be emptied. Choose one with a larger tank so you don't have to empty it as often, or a tank with a garden hose attachment that can be directed to a drain.

Note that the units you'll find are, essentially, refrigerators, with compressors and cooling coils. Below about 65 degrees F, ice will form on the cooling coils, reducing efficiency to near zero. In other words, they won't work well in cooler environments that are humid.

Being a refrigerator, they will give off heat into the room. In very small spaces (e.g. closets) they can heat the space considerably, enough to burn-out the dehumidifier. If that is relevant, buy one with a thermal protection sensor.

Depending upon the conditions you have, you might be able to lower the RH sufficiently simply by increasing the temperature of the space. (As temperature goes up, without adding additional moisture to the air, RH goes down.) If you know the temperature of the space and the current RH, it is easy to estimate by how much you'd need to increase the temperature to obtain a target RH.

[tjp]

Thanks Charles! More great information - especially the below 65 degrees part. Heck, that place won't see over 65 til April...

And all discussion is good in my book. Hijack away, maybe I'll learn something.

[Shuksan]

tjp an Carey -

There are a number of websites with info on how to decide what dehumidifier capacity would work for your space. They have tables showing capacities (pints of water per day extracted from the air) versus the square footage of the space and the degree of ambient humidity. It's worth looking a multiple sites because the recommendations vary a bit from one to another. Also, look at reviews of models to see what features would work best for you.

To give you a ballpark idea of what you might be looking at, I have a Frigidaire 30 pint dehumidifier for a 20' x 20' shop space with 10' ceilings. It's sufficient to drop the humidity from 70% to 40%. It has to be running pretty much constantly to do that but the unit is pretty quiet so I don't have a problem with that. With the starting humidity in the 60-70% range, it fills the collection reservoir about one and a half times in 24 hours.

This is the one I have: https://www.amazon.com/Frigidaire-30...t+Dehumidifier


To go with this, you will need to be able to measure the humidity accurately. The Frigidaire unit displays humidity numbers but they are in intervals of 5% so not enough resolution for guitar building and I wouldn't count on the accuracy of the hygrometers built into dehumidifiers anyway. You need a separate hygrometer and you need to calibrate it. There's a very good discussion of how to do this on this thread:
http://www.anzlf.com/viewtopic.php?t=6123

I have two digital hygrometers that I calibrate twice a year using the potassium carbonate method as described in the linked thread.

[Carey]

Charles T and Shuksan, thanks for that information; it's very helpful.
Cool and damp are my conditions for the next few months, anyway,
so I'll start with a heater and see how that goes.

[runamuck]

I don't have a humidity controlled shop so when the RH get's too high or low, I put glued up parts in a waterproof plastic box along with Boveda RH controllers.

https://bovedainc.com/store/music/hi...rption-boveda/

Note that thin pieces of wood like tops and backs adapt to RH changes quickly.

[Quickstep192]

I think a heater will only help if it's one that exhausts combustion gasses to the outside.

I have two big dehumidifiers in my shop during the summer. Get the kind that lets you hook up a hose so it can drain continuously. Both of mine came from yard sales for less than $100

[mirwa]

When being commissioned to build a guitar for someone, it is really not that great of an added expense to humidify your work space.

Having a humidified work space can save you time and heart ache during the build and at completion with warranty issues later.

Lots of people build / repair in non humidified work environments but they are blessed with very stable climates.

I do not humidify my workshop, I am one of those lucky ones with an incredibly stable environment, that being said, I have a device which monitors humidity in every room of our workshop.

Steve

[charles Tauber]

Originally Posted by Quickstep192

I think a heater will only help if it's one that exhausts combustion gasses to the outside.

In the winter, I use a small electric heater: no exhaust. In the coldest part of the winter, I add an electric oil-filled radiator-style heater. I do have to ADD humidity in this climate: I use a drum-style floor-model humidifier.

Both of mine came from yard sales for less than $100

Good deal.

[charles Tauber]

Originally Posted by tjp

As of last night, it was 70% in the shop (unheated detached garage), in the house, humidity was mid-50's. I have the top and back hanging out in the house near the woodstove for now, thinking I can do humidity-sensitive work out in the shop during the day, when it is warmer and humidity is lower, bringing pieces into the house to store it.

One issue is gluing and finishing in low temperatures and high humidities. Depending upon the finish you plan to use high humidity can cause application problems, as can low temperatures.

It is possible to do assembly work in an uncontrolled environment and then put them back into a controlled environment. Charles Fox arranged his shop that way back in the 1970's. He had a large shop with numerous rooms that were not environmentally rigorously controlled, and a much smaller storage space that was rigorously controlled. As each operation was finished, it would go back into the controlled space.