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Interseting topic on Hummidity and Digital readers

Del Nilppeznaf

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Here is a post listed on the Luthiers site Frets.net concerning RH... not meant to cause any alarm but all the talk about hummidity levels here and how people moniter them


i thought some would find it informative:


RH is a topic that we have done a lot of research on and testing as well.


First, as Jeff rightly said, your digital hygrometer likely sucks. No offense intended, in our experience every digital hygrometer except the multi-hundred dollar ones that we tested completely and utterly sucked. Even the very few that did come in close had the issue of range. What I mean by range is that they may be close to accurate in say the 40 - 50% range but above and below this they can be 20% off....


There is no substitute for a wet-blub test and all you need to do this is two lab thermometers, some gauze, something to move air, a few drops of water, and Internet access for the conversion charts. There are also variations on the wet bulb such as sling psychrometers and psycholdynes (spelling error likely...). In both cases it's simply a wet bulb test that is either employing humans to move the thing or electricity to turn a fan.


It's important too to understand that RH is constantly variable. Move across the room, breath in the right direction, and it can skew your readings. This is why when one purpose-builds a Lutherie shop specifically for instrument building doing all that we can to contain the space, insulate it, vapor barrier it, etc. is a good idea.


Below are some pics of some of the hygrometers that we have tested:




What I do is do the wet-bulb test either with a psychro-dyne (got it out to see how to spell the thing...) or use my two lab thermometers and do a wet bulb test. I compare the results approximately twice a year to my Abbeon and then calibrate, if need be, the Abbeon to match the results of the wet-bulb tests. Even though I do this around every 6 months the analog hygrometer does drift a bit over time. My experience has been very little drift, perhaps no more than 2% but it's enough for me to want to recalibrate the thing. You can also send Abbeons to California to the company for calibration including two levels of calibration of which one level is more expensive and to a NIST standard.


Here is my Abbeon and it's what I look at daily when building. Since it's calibrated against an actual wet-bulb I am sure that my readings are pretty close and this gives me great piece of mind. Again, your shop space and doing all that you can to stabilize RH is hugely important too. My shop was purpose built, insulation, vapor barriers, and built on sand, a giant kitty litter box so to speak...




Something else that is worth a good conversation is what RH is right for you, Peter, where you are. I shoot for 42 - 48% here in the midwestern US but in other climates this range may not be correct especially if the resulting instruments are to live in other climates. More specifically what I am saying is that for example instruments built in Arizona where it is very dry and if they are staying in this dry climate a much lower RH range is probably a decent idea. Conversely instruments intended for wet climates and built in same likely would do fine built in a higher RH range. Where we get in trouble is an instrument built at say above 55% RH that moves to a desert climate - I can hear the cracking now....


Anyway RH is important, it's not an easy subject either in so much as it's constantly variable and yes temp does impact it too. RH stability in a desired RH range is the goal and in my experience the only way to get there is a purpose-built area/shop or the perfect climate...


And before anyone suggests that the great violin makers or classical makers of Europe didn't have Abbeons what they likely did have was experience with RH from the school of hard knocks. This experience told them that certain times of year were better for certain things such as during the wet season make your apprentice cut lots of wood and during the "correct" season time to glue-up braces. It was less precise of course but how many of these instruments are still singing?


And lastly a very related topic is seasoning. Seasoned wood is more forgiving with RH swings where unseasoned wood isn't.... As such I won't build a thing unless the wood has been in my stash for at least five years.


Here is link to the page






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