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Visual aid for relative humidity
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10101&t=50212		 Page 1 of 2
Author:  Bryan Bear [ Fri Jan 19, 2018 7:12 pm ]
Post subject:  Visual aid for relative humidity
I get tired of doing wet/dry bulb measurements in my little basement shop. I made this quick and dirty pointer to hang right above my bench. It is nothing more than two strips of cross grain WRC mounted in a block. I measured the RH today and marked the 43% reading on the backboard. When I see it swing away, I’ll take more measurements and make more marks. Really all I need is a mark for the three bears (too high, too low and just right).

Is it a precision instrument? No. But, it will be in my face whenever I am in the shoppe keeping RH in my mind. I’m already thinking about making a really nice looking one to replace it.

Image


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Author:  Glen H [ Fri Jan 19, 2018 7:40 pm ]
Post subject:  Re: Visual aid for relative humidity
Great idea. Is that a chisel rack made of high flame wood?
Author:  J De Rocher [ Fri Jan 19, 2018 7:46 pm ]
Post subject:  Re: Visual aid for relative humidity
I think having one of these is a good idea. The one below made out of scrap wood has been on my wall for a few years. The business part of it is an off cut from the end of a spruce top plate with a thin strip of long grain mahogany glued to it. I assembled it at 45% RH and glued an indicator/pointer to the backing board aligned with the part that bends so it's easy to see at a glance even from across the room whether the RH is above or below 45%. In the photo, the RH is a little below 45%. I may get around to making a nicer looking one someday too.

Attachment:
Hygrometer - scrap wood.jpg
Author:  Bryan Bear [ Fri Jan 19, 2018 7:58 pm ]
Post subject:  Re: Visual aid for relative humidity
Glen H wrote:
Great idea. Is that a chisel rack made of high flame wood?


Ha! No not at all. It is just OSB with a layer of luan on top. Basically scrap, but it allows me to easily change the layout without having to put more screw holes in the drywall. Luan looks pretty good with some amber shellac.

My bench is a big U shaped workstation that I made from the kitchen counters that were here when I moved in, 2x lumber and some craigslist cabinets. I made some OSB and luan inserts for the sink and cooktop cutouts. This gives me a good place to do chopping and other chisel work. They lift up to allow me to store stuff underneath and I can replace them when they get messed up. The white Formica is great because stuff doesn’t stick to it and I can draw or do calculations on it then just erase it when I’m done.
Image
Author:  dzsmith [ Fri Jan 19, 2018 8:13 pm ]
Post subject:  Re: Visual aid for relative humidity
Great idea!
I bought a recommended analog meter. I waited and waited to spray lacquer, but the gauge showed 85% humidity. I happened to check the local forcast, and humidity was 40%.
I found a digital meter that closely matches the local weather channel that I now use.
I have three guitars still hanging that I could have sprayed. Man, I was pissed.
I think I’ll make me one of those goobers as a sanity check.
Thanks!
Dan
Author:  Bryan Bear [ Fri Jan 19, 2018 8:19 pm ]
Post subject:  Re: Visual aid for relative humidity
Just remember the forecast can be drastically different than your indoor RH.
Author:  dzsmith [ Fri Jan 19, 2018 8:21 pm ]
Post subject:  Re: Visual aid for relative humidity
Bryan Bear wrote:
Just remember the forecast can be drastically different than your indoor RH.

I work in the garage with doors and windows open.
I’m at the mercy of the weather.
Author:  Chris Pile [ Fri Jan 19, 2018 8:41 pm ]
Post subject:  Re: Visual aid for relative humidity
The late great Don Teeter built his own meter like that from scrap wood. He had pix and directions in his books about guitar repair.
Author:  DennisK [ Fri Jan 19, 2018 8:47 pm ]
Post subject:  Re: Visual aid for relative humidity
These are arguably more accurate than proper hygrometers, because of the hysteresis effect. If the humidity goes from high to low, any wood in the room will retain a bit more moisture than the air. If humidity goes from low to high, the wood will remain a bit drier than the air. What we really need to know is the moisture content of wood in the room, not the RH% of the air. And that's exactly what a wood hygrometer measures.

Something like a neck blank will take significantly longer to acclimate than the thin hygrometer strip, but should eventually settle to the same moisture content.
Author:  Bryan Bear [ Fri Jan 19, 2018 9:04 pm ]
Post subject:  Re: Visual aid for relative humidity
That’s a really good point. I was thinking about how this would be slower to respond to changes in RH and I would always wonder if I am in the lag. But, this is the same thickness as the typical top plate and should respond similarly to any top I happen to be working on. So this will really tell me what I am most concerned about; can I glue my braces and or close the box. Sometimes I run a space heater in my shop (about 180 square feet) to drop the humidity for bracing and whatnot. I always wonder if the plates and braces are acclimated. Now I’ll have a fair idea where the actual wood stands.
Author:  Haans [ Fri Jan 19, 2018 9:37 pm ]
Post subject:  Re: Visual aid for relative humidity
Congratulation to all of you that are taking this VERY seriously! This is actually the first step toward successfully building instruments.
Author:  bluescreek [ Sat Jan 20, 2018 10:17 am ]
Post subject:  Re: Visual aid for relative humidity
you made a mistake in assuming your hygrometer was accurate . Never assume check It is east to do a test
a table spoon of salt add water place hygrometer in the bag with the wet salt , In a few hrs it should read 75%.

I check every one I get and 25% are within 10% and I bet half are off by 30% if I am lucky 20% are on the money the worst ones I ever had were the digitals. Look to be sure you can adjust to calibrate them if not don't get it.
Author:  Colin North [ Sat Jan 20, 2018 12:09 pm ]
Post subject:  Re: Visual aid for relative humidity
Gotta make me one of those to go with my other 3. Trouble is finding somewhere to hang it!
Author:  Tim Mullin [ Sat Jan 20, 2018 12:10 pm ]
Post subject:  Re: Visual aid for relative humidity
bluescreek wrote:
you made a mistake in assuming your hygrometer was accurate . Never assume check It is east to do a test
a table spoon of salt add water place hygrometer in the bag with the wet salt , In a few hrs it should read 75%..

Great advice here. A non-calibrated hygrometer is next to useless. While table salt is readily available in any kitchen, 75% humidity is well outside the range we need for lutherie use. The exact same calibration test can be done using potassium carbonate, producing an equilibrium RH of 43% — right about where we need accurate readings. I found reagent grade pretty easy to source online and I recalibrate all our digital hygrometers once a year.



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Author:  J De Rocher [ Sat Jan 20, 2018 12:19 pm ]
Post subject:  Re: Visual aid for relative humidity
bluescreek wrote:
you made a mistake in assuming your hygrometer was accurate .


Well, in my case, I did not assume my hygrometer was accurate. I had calibrated it with a potassium carbonate test before I made my high tech scrap wood hygrometer.
Author:  Bryan Bear [ Sat Jan 20, 2018 12:21 pm ]
Post subject:  Re: Visual aid for relative humidity
J De Rocher wrote:
bluescreek wrote:
you made a mistake in assuming your hygrometer was accurate .


Well, in my case, I did not assume my hygrometer was accurate. I had calibrated it with a potassium carbonate test before I made my high tech scrap wood hygrometer.


Wet bulb test here. I should probably break down and get some potassium carbonate though too.
Author:  Alex Kleon [ Sat Jan 20, 2018 1:01 pm ]
Post subject:  Re: Visual aid for relative humidity
I got this Barigo hygrometer from the Twelfth Fret guitar shop in Toronto to replace a broken Abbeon. They double check the factory settings, and provide free, lifetime adjustments at their store. Thanks to Josh House for the recommendation!
Image

Alex


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Author:  bcombs510 [ Sat Jan 20, 2018 3:21 pm ]
Post subject:  Re: Visual aid for relative humidity
Is something like this one from Abbeon suitable or do I need to get into the multi hundred dollar ones.

Abbeon 5063.33 Humidity and Temperature Dial Indicator with White Face and Stainless Steel Case https://www.amazon.com/dp/B00YGI2D70/re ... yAbFGA4EXW

Brad


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Author:  J De Rocher [ Sat Jan 20, 2018 4:06 pm ]
Post subject:  Re: Visual aid for relative humidity
Based only on my experience, an expensive hygrometer isn't necessary. I've used a Planet Waves digital hygrometer for the past five years. I have calibrated it with a potassium carbonate test once each year and it always gives the same result. The displayed value is consistently 2% high. So I just subtract 2 points from the displayed value. A couple months ago it briefly displayed values a couple times that were clearly low by about 10% so I got a second one. An AcuRite digital for $15.29. https://www.amazon.com/gp/product/B01HDW58GS/ref=oh_aui_detailpage_o01_s01?ie=UTF8&psc=1
Out of the box it displayed 1% high based on the potassium chloride test. The two hygrometers always read with in 1-2% of each other. I suspect differences between their displayed values result from differences in how fast they respond to changes in humidity.

The Abbeon you linked to has the advantage of being readable from a distance. Neither of the digital ones I have can be read from across the room.

One thing I noticed when looking at hygrometer specs is that the claimed accuracy for RH values varies quite a bit and doesn't necessarily correlate with price.
Author:  AndyB [ Sat Jan 20, 2018 5:32 pm ]
Post subject:  Re: Visual aid for relative humidity
Problem with battery powered hygrometers is, the battery can go low, but it continues to show a value. The wrong value. Ask me how I know. I use Abbeons now. Buy them used on eBay. Dirt cheap - nowhere near as expensive as ruining a guitar.

Andy
Author:  bcombs510 [ Mon Jan 22, 2018 8:10 pm ]
Post subject:  Re: Visual aid for relative humidity
So I got two new digi and one new mechanical hygrometer. They have been sitting in my living room for about 4 hours. The third digi is the one I already had.

The three digi are pretty close but the mechanical one hasn’t adjusted to the humidity. Is it maybe bad and I should return it? The manual doesn’t say anything about setting it up or enabling it in any way. Just about calibration.

Image

Brad


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Author:  Mike OMelia [ Mon Jan 22, 2018 8:55 pm ]
Post subject:  Re: Visual aid for relative humidity
Bryan Bear wrote:
I get tired of doing wet/dry bulb measurements in my little basement shop. I made this quick and dirty pointer to hang right above my bench. It is nothing more than two strips of cross grain WRC mounted in a block. I measured the RH today and marked the 43% reading on the backboard. When I see it swing away, I’ll take more measurements and make more marks. Really all I need is a mark for the three bears (too high, too low and just right).

Is it a precision instrument? No. But, it will be in my face whenever I am in the shoppe keeping RH in my mind. I’m already thinking about making a really nice looking one to replace it.

Image


Sent from my iPhone using Tapatalk


How cool. Smart idea Bryan. My procedure is to note if wood looks like a potato chip. Gonna build one of those.
Author:  J De Rocher [ Mon Jan 22, 2018 9:28 pm ]
Post subject:  Re: Visual aid for relative humidity
bcombs510 wrote:
So I got two new digi and one new mechanical hygrometer. They have been sitting in my living room for about 4 hours. The third digi is the one I already had.

The three digi are pretty close but the mechanical one hasn’t adjusted to the humidity. Is it maybe bad and I should return it? The manual doesn’t say anything about setting it up or enabling it in any way. Just about calibration.

Brad
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The product description on Amazon says "Tested at three different humidity positions and includes a certificate of accuracy." so that's strange that it reads so different from the other three meters. I would be inclined to send it back. You could do a potassium carbonate calibration on it, but if it's truly that far off from the other three (assuming they are giving valid readings) after having been tested at three humidity levels by the manufacturer, I wouldn't trust it.
Author:  bcombs510 [ Mon Jan 22, 2018 9:47 pm ]
Post subject:  Re: Visual aid for relative humidity
J De Rocher wrote:
The product description on Amazon says "Tested at three different humidity positions and includes a certificate of accuracy." so that's strange that it reads so different from the other three meters. I would be inclined to send it back. You could do a potassium carbonate calibration on it, but if it's truly that far off from the other three (assuming they are giving valid readings) after having been tested at three humidity levels by the manufacturer, I wouldn't trust it.


Thanks, Jay. In the manual it’s hand signed by the tester who tests on 3/17 and marked it as accurate +/- 2.5%. So something seems wrong. I’ll exchange it through Amazon.

Thanks!
Brad




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Author:  bcombs510 [ Mon Jan 22, 2018 9:47 pm ]
Post subject:  Re: Visual aid for relative humidity
BTW: I have some potassium carbonate on the way too. :)


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