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Hygrometer a hair better

Posted: Thu Oct 04, 2007 10:31 pm
by Craig

It may look a bit hairy , but is actually very accurate.

I knocked this up a couple of years ago and it lives next to my digital hygrometer . Just as accurate or probably more so .

It's made from three strands of my daughter's hair ( about 9 " long).

Human hair has been proven to be the most sensitive and stable material known for humidity control .

This is all scientists used a hundred years ago , and even today , if you were to buy a top of the range hygrometer , it would more than likely be made from human hair ..

Try one yourself !

Posted: Thu Oct 04, 2007 10:51 pm
by Kim
Very clever but extravagant Craig, I may make one too but shall economize a little and use an old 1c piece :D



Posted: Fri Oct 05, 2007 6:04 am
by BillyT
That is so cool! How do you ... calibrate that thing?

Posted: Fri Oct 05, 2007 7:26 am
by Craig
I'll also add that human hair has an exclusive tension release device that keeps the hair strands from being damaged by extreme humidity or mechanical strain.

As far as calibrating is concerned , Paul ,our local scientist may be able to help out further here. As a starter, I soaked the hair in water and marked that on the guage as the most extreme. I then dryed it fully with a hairdryer and marked that as the other extreme. From there , I have tryed to fine tune it over several months, from my digital hygrometer and local weather station humidity readings.I think I now have it reasonably close

It really does work very well and have come to rely on it more than the digital one.

I did clean the hair strands a number of times to rid it of any conditioners etc. that Sophie (my daughter) may have used. The professional units employ about 150 strands.

Posted: Fri Oct 05, 2007 8:42 am
by Arnt
My German built, good analog hygrometer has a human hair (or hairs, I don't know the number) as a humidity sensor. I opened every box on the shelf in the store that sold them (I'm a good customer; usually!), and they were all just a couple of % apart. I took that as an indication of quality and accuracy, so I trust it. It can easily be calibrated of course. I have two or three digital hygrometers too, but they don't agree with each other or the good one; well one of them pretty much constantly show 10% higher humidity than the analog one, but alas, it cannot be adjusted. Hair hygrometer: good!

Yours is a lot more elegant of course, Craig. Good job!

Posted: Fri Oct 05, 2007 9:04 am
by Paul B
Me and my Physics professor at uni pulled the back off one to have a squiz inside - I hadn't believed him when he told me it used hair. It was an expensive one too, very accurate.

Craig, the only significant difference between yours and his was a spring instead of a weight, and his had more hair - unlike the good prof.

Back in the old days they'd calibrate it against standard saturated salt solutions. These were just a beaker of water with as much salt as could be disolved in them at a given temp (usually 20 or 25 deg C). Stick one of these beakers in a sealed box (or plastic bag) and you'll have a known level of humidity. There's all sorts of salts you can use, each one will give you a different level of humidity. We still use this method in the lab for controlling humidity in a glass bell jar.

But how accurate would an old time luthier need? My guess is they'd only need two graduation marks on their scale. If the needle is between the marks you're good to go, if it's not you need to go make necks or whatever.

Probably stretching it a bit I know. But I was interested in what the fella who claims to be reproducing stadivarious sounding violins had to say. He's soaking wood in salt solutions - impregnating the timber with salts. It's concievable that old strad had some salt solutions to hand...

Posted: Tue Oct 09, 2007 7:03 am
by matthew
I wonder if horse hair is as sensitive and accurate?

Have you seen this article about humidity cycling? The guy uses salt solutions to standardise humid environments to put instruments through a cycle of humidity changes to relieve stresses. ... ycling.htm

I believe you can do the same thing by working slowly and leaving your rib garland/top/back out in the garden shed for a while to de-stress in the changing weather. Others spray acompleted rib garland with water and allow to dry, several times. It makes sense to me.


Posted: Tue Oct 09, 2007 8:56 am
by Paul B
Yes horse hair has been used in horse hair hygrometers for probably centuries. I don't know if it's as sensitive, but it certainly works with a high degree of accuracy.

That was an interesting article, quite at odds with the current thinking in the guitar world. Most guitar makers will tell you that a controlled environment for wood storage and in the workshop environment, is highly desirable. Perhaps this is to do with guitars being made from large thin plates that are more likely to split?

I did notice that he didn't cycle down below 44%, so he's not drying the wood out too much.

Oh, and what he said about varnish being a moisture barrier - we'll yes to an extent, it's not until you start measuring moisture ingress through thin film "moisture barriers" that you realise "barrier" might not be the right word. It'd certainly have a dampening effect on moisture ingress (and egress) but doesn't stop it.

Posted: Tue Oct 09, 2007 9:53 am
by matthew
Problem with a controlled environment is that when the instrument gets "out there" the environment becomes totally uncontrolled.

The idea with the humidity cycling is to get all the extremes of warping and twisting over and done with while in the shop. This allows the maker to adjust and "tune" the instrument for best response. Perhaps is more useful in violins etc because there is much less bracing involved.

When my first bass top was on the bench it used to twist and warp at the corners so much I thought it was going to fly away. But after a while, the extremes of movement became less and less, i guess as the thing stabilised. Same for the ribs, they'd try to twist and flatten at first, then after some time out in the shed they stabilised nicely.

Its still important to glue up in a nice dry environment so that future shrinkage is minimised.

BTW. What do i have to do round here to get rid of "pallet wood" under my name?

Posted: Tue Oct 09, 2007 10:40 am
by Kim
In the same vein as Mathew's post, I know of a very knowledgeable builder/tonewood seller in the USA who advocates NOT storing tonewood in a controlled environment. He stickers and end-grain seals his wood and allows it be exposed to all the changes that nature can throw at it, under a shed roof, for as long as he can. A few weeks out from a build, he selects his sets and takes them into the RH controlled build room.

He explains that as the wood expands and contracts with the changes out in the shed, it does so to lesser degree each time and, as Mathew suggest, relieves a lot of the stresses. After cycling for a few years, the wood settles right down, sort of like baking spruce I would imagine.

Apparently, a lot of the Spanish masters simply stored their wood directly under the roof of an open sided shed, here it would be exposed to repeated seasons of heat from the blazing Spanish sun and moisture from rains all the while being ventilation by any available breeze.



Posted: Tue Oct 09, 2007 10:46 am
by Kim
matthew wrote: BTW. What do i have to do round here to get rid of "pallet wood" under my name?

I think the pallet wood label will go when you have made more than 10 post and the tag will change to more desirable titles as you reach certain bench marks in the number of post made.

Oh and welcome M8, nice to have you with us. :D



Posted: Tue Oct 09, 2007 10:46 am
by BillyT
If I use an American dime, considering the dollars fall, does this change the calibration at all, you think? :lol:

Posted: Tue Oct 09, 2007 11:07 am
by matthew
I discovered the humidity (and temperature!) cycling effect when I was building my first bass under an open car-port.

There. Has that taken care of the pallet? YES!

Posted: Wed Oct 10, 2007 4:37 pm
by kiwigeo
What Craig has neglected to mention is that his girlie hair hygrometer needs a shampoo at least once every two days and after each shampoo session it needs to sit wrapped in a towel for at least 3 hours.

Posted: Wed Oct 10, 2007 10:08 pm
by Craig
Yeah ,I'd say You'd probably need to recalibrate Billy :lol: .

I'd send you this one Billy but I'd have to rebuild it to work upside down.

Don't forget the blow wave job Martin , and maybe just a touch of gel,,, ooo La la

Posted: Thu Oct 11, 2007 12:18 pm
by BillyT
I'd send you this one Billy but I'd have to rebuild it to work upside down.
:lol: :lol: :lol: :lol: :lol:

Er! You mean right side up? Right! :lol: :lol: :lol: :lol:

Posted: Sat Oct 13, 2007 9:02 pm
by joel
Well, you learn something new every day! Now I need to go out and make a hydrometer... I wonder what colour hair will work best? My wifes red or my daughters blonde?

Posted: Sat Oct 13, 2007 9:36 pm
by Kim
Hey Joel,

Welcome to the ANZLF mate. :D

Funny you should say that about your wife and daughters hair colour, I have the exact same circumstance. Just wondering, do you think the red hair thing is natures way of giving us blokes some kind of warning??

Seems to work that way with spiders and snakes and stuff, and every since I got involved with this obsession, it would seem pretty accurate in relation to the better half also :lol: :lol: :lol:



Posted: Sun Oct 14, 2007 9:32 pm
by joel
I'm not allowed to comment on the "red hair" thing... :shock:

I'll probably use my daughters as it's finer and will probably react faster. And she'll think it's cool that we made a tool out of her hair.

Posted: Sun Oct 14, 2007 10:58 pm
by Kim
joel wrote:I'm not allowed to comment on the "red hair" thing... :shock:

I'll probably use my daughters as it's finer and will probably react faster. And she'll think it's cool that we made a tool out of her hair.
Don't worry Joel. I always get the last words in my house too...."Yes Dear" :lol: :D