Maintaining Humidity

Construction and repair of Classical Guitar and related instruments
BellyDoc
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Re: Maintaining Humidity

Post by BellyDoc » Sun Mar 04, 2018 9:10 pm

The height of the cabinet is unaltered from the armoire that I modified, but I did consider lowering it at one time. I could have trimmed off the legs and altered the front cross-brace which has some low hanging decorative scallops. That would decrease the height by 5 inches (13cm). I considered that when I was thinking it might be nice to put against a wall with some small high windows that would not be partially blocked if the piece were just a few inches shorter. Ultimately, I didn't put it in that spot and left it as is. With more extreme modification, I probably could have shaved 9 inches (23cm) by cutting into legs and base boards all the way around, before the doors would be low enough to need consideration in terms of carpet clearance.

The instrument-containing portion of the cabinet is above a shelf that I built inside, the height of which aligns with where the door panels were replaced with glass. Below that shelf is some space mostly for the humidifier (salt solution bucket) which is about 14 inches (36cm) high. Above that shelf, the space for the instruments is about 48-52" (1.22-1.32m) high and is very adequate. However, I would have been perfectly happy if I had instead found a lower cabinet with 48 inches of height for the guitars, but less for the humidifier.

Of note, with the height were it is, I have a straight-in view of the instruments. I reach in and can see well as I remove a guitar, which I enjoy. I think I would be more likely to bump the guitars against each other if the doors were lower to the ground because my view would be partially obscured.


To get the doors to seal, I first removed them and spent some time grinding away at the top and bottom edges to correct some warpage, so they would sit flat against the carcass. Next, I built a lip inside the doorway as a sealing surface. I installed the lip with a gap from the doors so that whatever sealing material I chose wouldn't have to compress to zero thickness for the doors to close completely. The toughest part was copying the curve at the top. After I applied finish and hung the doors, I chose weatherstripping material appropriate for the gap. I did not use a center pillar for the two doors to seal on, and instead made the two doors seal against each other. For that, the gap between the doors got two seals, one affixed to the left door at the back of the gap, and one on the right door along the front of the gap. As a result, the doors can only open and close together because the seals compress tight. If I try to open the right door, friction opens the left too. I used 4 cabinet door magnets to help keep the doors shut and sealed, but it turns out that the compression of the right door-left door seal creates it's own catch mechanism. The result appears to work quite well.


Edited to incorporate a superior measuring system :)
"If I have seen further it is by standing on the shoulders of giants." -Sir Isaac Newton

Armin Hanika 56PF

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rojarosguitar
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Re: Maintaining Humidity

Post by rojarosguitar » Sun Mar 04, 2018 9:24 pm

Thanks for the exact information.
About the superior measuring system I don't know, it's more about habits, I think. Actually I think the English and North-American craftsman have the advantage of habitually calculating fractions, whereas Europeans need an electronic calculator as soon a fraction appears :D
Music is a big continent with different landscapes and corners. Some of them I do visit frequently, some from time to time and some I know from hearsay only ...

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BellyDoc
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Re: Maintaining Humidity

Post by BellyDoc » Sun Mar 04, 2018 10:49 pm

You're right. "Superior" may be a bit strong. Centimeters and millimeters are very useful, but I do enjoy the sense of history infused into the Imperial system too. It turns out that many of the seemingly strange numbers chosen in the grouping of units such as 12 inches, 24 hours, 60 minutes, 360 degrees... they're called "highly composite numbers" because of having so many natural number divisors. It's an intuitively useful technique to use this type of number for unit divisions. We obviously gravitate to that sort of halve-and-halve again logic in many arenas.

For example, I would personally find it difficult to play music notated in 10th notes.
"If I have seen further it is by standing on the shoulders of giants." -Sir Isaac Newton

Armin Hanika 56PF

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rojarosguitar
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Re: Maintaining Humidity

Post by rojarosguitar » Mon Mar 05, 2018 9:54 pm

BellyDoc wrote:
Sun Mar 04, 2018 10:49 pm

For example, I would personally find it difficult to play music notated in 10th notes.
What a horror idea :lol:
Music is a big continent with different landscapes and corners. Some of them I do visit frequently, some from time to time and some I know from hearsay only ...

My Youtube Channel is: TheMusicalEvents
My homepage is: https://www.live-arts.de

Rasputin
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Re: Maintaining Humidity

Post by Rasputin » Mon Mar 05, 2018 10:02 pm

Watch out, Council Directive No 666/2018 is coming to impose SI notation on all of us... well all of us in the EU.

It's a good point that all those 12s made a lot of sense in a pre-electronic age where it was more practical to use fractions. It doesn't seem to work across the board though - 16 ounces in a pound, 14 pounds in a stone, 20 shillings in a pound, 20 fluid ounces in a pint...

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prawnheed
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Re: Maintaining Humidity

Post by prawnheed » Tue Mar 06, 2018 12:34 am

Rasputin wrote:
Mon Mar 05, 2018 10:02 pm
.. 20 fluid ounces in a pint...
More confusing is that, in some parts of the world, there are 16 fl oz in a pint.

BellyDoc
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Re: Maintaining Humidity

Post by BellyDoc » Tue Mar 06, 2018 5:02 am

"Pounds" aren't even necessarily all the same. A pound of gold is measured in Troy weight, which is 12 Troy ounces, which are different from the Avoirdupois/Imperial ounce. A Troy pound is 5760 grains and the Imperial pound is 7000... and those are the same "grains", so the Imperial pound is heavier.
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Armin Hanika 56PF

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prawnheed
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Re: Maintaining Humidity

Post by prawnheed » Tue Mar 06, 2018 3:27 pm

Fluid ounces are also not the same. A US fluid ounce is slightly bigger than an Imperial fluid ounce.

All-in-all, much better all round to move to the SI system in which units are not ambiguous.

There is no reason why one couldn't continue to use non-decimal fractions of a metre or kilogram etc. if one so desired. I frequently ask for half a kilo of meat rather than five hundred grams for example.

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rojarosguitar
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Re: Maintaining Humidity

Post by rojarosguitar » Wed Mar 07, 2018 5:50 am

After this little digression into unit systems I have a practical question @BellyDoc: this saturated solution, how does it behave over time? Is there some organic growth or fungus or whatever? Is it to be replaced in regular intervals? How long can it be kept, or how often does it need to be exchanged?
Music is a big continent with different landscapes and corners. Some of them I do visit frequently, some from time to time and some I know from hearsay only ...

My Youtube Channel is: TheMusicalEvents
My homepage is: https://www.live-arts.de

BellyDoc
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Re: Maintaining Humidity

Post by BellyDoc » Thu Mar 08, 2018 12:28 am

The degree to which it evaporates will be a function of the difference between ambient humidity in the container, and it's equilibrium value of 43.5%RH, and also the size of the container. In my cabinet, which gets opened 2 or 4 times in a day, I've topped off the container water 3 times since I began using it in October. At no time was there a total loss of fluid. I'd estimate I replaced about 150mL of fresh water for a 6 week average interval. Each time I've added water, I've used our reverse osmosis tap, and I've knocked salt concretions off the filter with it, back down into the bucket. Each time I've done that, the hygrometer reading has risen to slightly over equilibrium for a few days afterward and then normalized.

I would be shocked, and maybe a little scared if anything could grow in that bucket. It's intensely hyperosmolar and more than a little alkaline. In fact, when I got the humidifier filter that I put in there to facilitate evaporation, I got one that had a mesh of thin metal, probably aluminum, around the outside. Well... THAT'S GONE!!... it dissolved!!! I presume I now have an additional salt of aluminum oxide in there. It doesn't appear to have changed the equilibrium value on the hygrometer so I haven't replaced the solution, but I would say it underscores that the harmlessness of "food grade" potassium carbonate is relative. This amount/concentration is probably a little on the corrosive side and I wash my hands after handling it. I do plan to replace the solution at some point, but for now it's educational to just watch the hygrometer and add some water now and then when the level falls noticeably.

Making up the solution at the front end deserves some mention, too.

Before I undertook this project, I did some experiments with different hygrometers, closed containers, and salt solutions. I wanted to learn about how the hygrometers worked, and what the response times were for those meters and for the salt solutions. I tried table salt, potassium carbonate, and pure water. I also got a "calibration kit" for hygrometers which is supposed to be a 75% standard (which is the equilibrium value for table salt, so save your money). Each time I made the "saturated solution" by putting a mound of salt in a little bowl, then moistening it with enough water to make it all look wet, but not enough water that the salt could dissolve. Each of these were MUCH more salt than water. I'd then put the hygrometer and the salt solution into a mason jar and watch it for a couple days. I tried a dial-based hygrometer, a couple digitals by Thermo-Pro and a Caliber IV. All worked just fine. Interestingly the dial worked pretty fast compared to my expectations for a cheapo thingie, and the accuracy wasn't horrible compared to the others. They're all within a couple of percentage points in the range I'm using them for. The dial was more off at 75% than the others, and still more off at 100% which is probably more important to know for cigars than guitars since we're not pushing those levels.

An interesting finding from that experience, though, was mixing K2CO3. It gets gummy and warm when wet. I figured that to make up a large batch of solution capable of keeping a whole cabinet appropriately humidified, I was going to need to use the whole kilo that I had purchased and make a maximal batch of solution.

I have a few lab supplies at home already, (saltwater reef tank supplies) and I used a 1 liter Pyrex Erlenmeyer flask and a magnetic mixer to dissolve the K2CO3. I started with about 400mL of water, and slowly added scoops of K2C03 while stirring. It got quite warm during dissolution, not enough to be uncomfortable to touch but probably the upper limits of comfortable. The literature said that the solubility was something around 115g/100mL, but unfortunately that's not exactly the number that I needed. This number tells you that 100mL of saturated solution is DENSE. 100 mL contains 115 grams of salt *AND* some water. How much water? ... no clue, but it's not 100mL because that 115 grams of salt takes up a fair amount of space. The number I really wanted was "how much water can I dissolve a kilo of K2CO3 into, in order to achieve a saturated solution?"

I would say the answer is only slightly more than 400mL.

I kept adding salt, creating a cloudy suspension of particles in water, and then letting it stir till it dissolved/cleared, repeating and repeating, letting it cool a bit between additions. Finally, when almost the whole kilo was in there, it wouldn't clear with mixing. At that point I had almost a liter of solution. The flask was quite full. I let it settle and there was some undissolved salt at the bottom proving that it was a saturated solution. I then decanted it into my bucket and threw the remaining grams of powder in for good measure.

So I got lucky but I almost didn't. If I had started with much more water, I would have been able to dissolve the whole kilogram of salt and still not achieve saturation. So, for my next batch, that's going to be my ratio again. I'm going to slowly mix a kilogram of K2CO3 into 400mL of water. I'm going to use a container that should hold substantially more than a liter and is heat resistant. I'll probably order a dedicated 2 liter Pyrex for the job, which may also become the actual holding tank. I may also omit the use of the evaporative filter because I don't think evaporation needs to happen quickly and I'm not certain how much salt is getting sequestered.

... sorry about the nerd-out. It's probably a doctor thing.
"If I have seen further it is by standing on the shoulders of giants." -Sir Isaac Newton

Armin Hanika 56PF

Dr ToneControl
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Re: Maintaining Humidity

Post by Dr ToneControl » Sun Mar 11, 2018 7:54 am

I bought some hygrostats a few years ago, with some basic humidifiers

The hygrostat plugs into the wall socket: it has 2 modes, one is to switch on when the room is too dry (what I want), the other is the opposite (for humid climates, to switch on a dehumidifier)

So, I now have the hygrostat plugged into the wall, and from it a 4 way socket block, into which I have 2 basic humidifiers connected
I can keep the room at a constant RH. Of course, since the wall socket is low, I need to compensate for that, so I typically set the humidity a little lower than I really want, and measure it at chest level with meters at the same height as the guitars hanging on the wall

Result: instant access to guitars, rather than having to open cases all the time, guitars stay in tune for months, action never varies, no frets sticking out because of shrinking fingerboards, or damaged bodies.

The only catch is that the humidifiers tend to burnout after a year or two

I think that a constant humidity in open air is better than being in a humidified case - surely the humidity varies around the instrument, and there is risk of over-humidifying certain parts of the guitar?

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rojarosguitar
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Re: Maintaining Humidity

Post by rojarosguitar » Sun Mar 11, 2018 9:57 am

Another good idea...
Music is a big continent with different landscapes and corners. Some of them I do visit frequently, some from time to time and some I know from hearsay only ...

My Youtube Channel is: TheMusicalEvents
My homepage is: https://www.live-arts.de

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rojarosguitar
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Re: Maintaining Humidity

Post by rojarosguitar » Sun Mar 11, 2018 10:06 pm

@DrToneControl: Can you please describe what you mean by a 'basic humidifier' ? I heard that after a while everything in the room is covered with a smeary coating film (hope I express it correct). What is your experience?
Music is a big continent with different landscapes and corners. Some of them I do visit frequently, some from time to time and some I know from hearsay only ...

My Youtube Channel is: TheMusicalEvents
My homepage is: https://www.live-arts.de

DaveLeeNC
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Re: Maintaining Humidity

Post by DaveLeeNC » Wed Mar 14, 2018 3:13 pm

How much water do you guys use to maintain humidity? I have a room humidifier which is hardly high end. I find that (here in south-central NC) it takes a gallon or more of water per day to keep a small room at 40% (barely) during heating season. Of course the problem is that this air gets dispersed fairly fast across the whole house. But that quantity of water is surprising to me and I was curious as to other folks (who are humidifying only one room) experience with how much water is used. Also we have a heat pump and these tend to run more at higher air flow than a typical gas/oil heating system, so that is certainly a factor here.

If it matters our entire house is around 2000 sq feet while the room I am dealing with is pretty small at 12x12.

Thanks.

dave
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rojarosguitar
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Re: Maintaining Humidity

Post by rojarosguitar » Wed Mar 14, 2018 3:29 pm

Inspired by the last contributions I ordered a humidifier, after the cabinet idea turned out to be quite difficult: finding a cabinet of right proprtions, appealing to my wife and to me at the same time, and last not least halfways affordable...

I'll report about my experiences with the humidifier, it should arrive next days.
Music is a big continent with different landscapes and corners. Some of them I do visit frequently, some from time to time and some I know from hearsay only ...

My Youtube Channel is: TheMusicalEvents
My homepage is: https://www.live-arts.de

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