Official Luthiers Forum!

I post this every year and it's that time again when the furnaces come on and every wooden musical instrument needs to be properly humidified. Your shops do too and job one of guitar building to me is and always has been doing what it takes to have a stable and appropriate relative humidity in your shop AND wherever any customer instruments may be too.

So this is my home stuff this morning and I have a Pschro-Dyne here too since I have a lot of guitars here.

Without going into details this is wet-bulb technology in a self contained unit that were used by industry for years. Digital hygrometers are not reliable and drift greatly. I know I will get some push back here and I don't care they are junk, all of them and we have tested all of the ones available beyond the $1,000 Honeywell offerings that no one is using for Lutherie anyway.

These old school hygrometers can be calibrated quite easily with the turn of a screw. Digital ones can have some value if you check them and write on them the error so you can always factor that in. If you use digitals I would calibrate them or at least check them twice a year but again I would not use them at all.

As Rod Stewart said every pic tells a story. The smaller hygrometer is the newer one and that one was 3% high and had drifted this much in it's first year here. The larger hygrometer I have had around 15 years and is always very close to spot on.

So I dialed down the small one 3% and we are good to go here for another cold, dry Michigan winter.

PS: My first year building guitars I read on this forum about a poster who was woken up at 3:00 AM by a loud crack sound. He went to his shop and his guitar under construction had cracked, the top had cracked. He had zero RH control in his shop and was bummed to the max. Don't be that guy.....

Thanks for looking!

One more pic that didn't make the eight pic limit.

Sure must be nice to have Hesh, but one of each comes to about 600+ smackeroos.
But I've had a couple of these for 2 years at 10% of that price, and they've been very well behaved.
Price difference, which some of us may find a consideration, is a lotta nice tops.
Checked regularly, I've never had to adjust them once in 2 years (check due again for the season - thanks for the reminder)
I run a BestAir HG050 Hygrometer and a Ikea Hair one (!) as well, which are good indicators, but no so perfect.
AcuRite 01080M Pro Accuracy Temperature and Humidity Monitor with Alarms
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=52642&p=692297&hilit=+hygrometer#p692297

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Hesh, that looks like a nice unit.

I’ll chime in to say that in the event a mechanical psychrometer isn’t available, manual sling psychrometers are cheap and can be a cost-effective way to sanity-check your other hygrometers. For years I got by with cheap digitals because I could always break out the sling psych to ensure things were where they needed to be.

I still use one to check my hair hygrometers every month or so.

Also, I have the human hair version of that synthetic hair Fisch unit Hesh showed… it’s quite accurate but requires “regeneration” (wrapping in a wet cloth for a couple hours) every few weeks to maintain its accuracy. I’d love to run it side-by-side with its synthetic counterpart to compare.

Your pricing is WAY above ours, I can get both of these for half of what you quoted.

So what do you check with? I am recommending some form of wet bulb testing which if you simply buy two lab thermometers can be done for under $10.

Exactly we have to have a "standard" that we use as the be all to end all and I can't think of a better one than a wet bulb test or variant on that theme such as a sling psychrometer. I used to use the digitals as a check em and then use them as a loose reference. We had a Caliber IV in the shop drift 13 points in one year and pitched it. When they are that far off they are dangerous and that false sense of security that a correct reading gives is quickly replaced by a very unhappy client who's guitar cracked in a repair center because they didn't maintain proper RH but preached that others should. So for us we can't take any chances and will go with what works.

Does this mean that the Luthier has to wrap a wet towel around our heads? Seriously that sounds pretty cool, I was not aware of this for the human hair version.

I have the same Abbeon as yours - I am constantly amazed how inaccurate my digital hygrometers are - especially the Honeywell one controlling my Aprilaire 800Z Steam Humidifier. Currently the Honeywell shows 35% RH, while the Abbeon shows 49%... I test the Abbeon every season with the salt water and bag test and it is always bang on....

Potassium Carbonate, saturated solution.

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Caliber used to say in their flyer that comes with their Hygrometer that it will void their warranty to use a chemical standard such as Potassium Carbonate. We always thought that this was Caliber's way of tying to not let the public know how inaccurate their hygrometers are.

For Dave Collins though he's not a fan of any of the chemical methods for creating a so-called lab standard. There is also the issue of range. Meaning that some digitals have the ability to be pretty accurate in certain ranged say 20 - 50 or 60 and above but they can be way off in the range that we want, 40 - 50. So we like wet bulb tech or some variation.

When I tested mine this morning the actual RH at the test location was 45% so I am in the middle of the desired range and dialing in even further.

I'll add that a digital hygrometer will break down in time as the chemicals they use for the reaction break down. These old school mechanical hygrometers could have 100 year useful lives with some care which greatly reduces the price vs. utility quotient.

Anyway as I mentioned I'm not looking to keep debating the same thing here year in and year out. We believe digitals to be misleading and inaccurate your milage may vary. And again I am not speaking of the higher price digitals tested and used in industry.

I have Pschro-Dyne too and calibrate every 6 months. Geesh are they really that expensive now? I think I may have paid like $100 bucks for mine but this was years ago too. I never spent a lot on a hygrometer but the important think is the one I have is adjustable. I typically have to adjust it a bit every 6 months.

Good reminder Hesh that it's time.

Hesh, Thanks for the reminder!

I like the Potassium Carbonate approach. It has an equilibrium of 43%, and it’s cheap and easy.

M

I would consider Honeywell to be one of the highest quality product you could buy too but I'm not surprised at your experiences with it, again every digital that we ever tested and we try to test them all sucked.

C
I'll take my chances checking calibration regularily.

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

So I'm really curious here about the high cost of the Psychro-Dyne instrument. I'm sure there's a lot i don't know about it so I'd appreciate it if someone could tell me why I couldn't make one out of a wet-dry bulb thermometer set and a tiny, battery operated fan, enclosed in a tupperware box with a few creative baffles and holes.

Looks like about a $20 project, but as I said, there MUST be more to it than that.

??

Hesh—

Could you elaborate on why Dave does not like using chemical methods? Assuming one uses Potassium Carbonate in the solution, range of accuracy is not the issue, because it creates RH in the sealed container of 43%, right where we want it.

Maybe it is a question of what is more convenient or what gives a faster result, but accuracy should not be the “ding” on the saturation method, if one uses the correct salt (Potassium Carbonate).

Not really. They are pretty simple instruments when you get down to it. I thing these were made to be carried in the field so they close up into a nice case and so on. But really it's just two thermometers, a little cotton sock to wet on one, and a fan.

Call me lucky but where I build here in Calgary, the humidity ranges from 25% to 50%. I'm a low volume local builder for friends and family so never have to worry about cracking which never happens in the 35% or so average around here with what I build. Bring a solid wood guitar from somewhere else could obviously be an issue. When I become rich and famous and start exporting guitars all over the world, I'll look into shop controls!

I've never understood how you can control humidity completely. At my house it doesn't make sense. This year was really dry all the way till the end of summer, then it got wet. Now the sump pumps been running pretty steady for a couple months. The back yard, starting about 100 feet from the house all the way back is better than it's ever been in 30 years,even after a spring melt after a lot of snow.
The dehumidifier has only been on about half a day the entire time. I turn it off. I dumped it maybe every other day, and now, even though the water is right under the floor and even seeping in now if it rains since the ground is so saturated, I haven't dumped it in 3 days.
It's a new unit. Set at 45%. The USELESS digital says around 42 all the time. An old spring? Thang I got with a clock for 10years service at a shop says about 25%
I've brought the digital up from the basement in the winter and 45 degrees downstars, to 65 upstairs, the humidity doesn't change hardly at all. I don't have forced air or heat down there, so you'd think it would change more.
I did have a couple fretboards fall off one night several years ago. Some kind of freak thing. Some wood got black dots on it too. And some potatoes went bad!
Don't know what that was.all about!

_________________
Why be normal?

IIRC it is potential for the sensor to be damaged/corroded(?) by the chemical vapours.

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Ken, you can control humidity easily with dehumidifiers and humidifiers provided you can seal your shop, or part of it, reasonably well.

I live in a subtropical climate where it’s basically damp (rh 65%+) for ten months of the year, with a couple of “dry” winter months where humidity might drop to 50%. My shop is too big to keep at 45% year round, so I enclosed a 9ft x 9ft area as a dry room. All wood and components are stored here, along with in-progress guitars and customer instruments that require certain types of work. All assembly and cross-grain gluing happens here. It’s easy to hold this space at 45%rh. My dehumidifier runs most of the year and drains via a hose through the wall so there’s no need to empty it.

The rest of the workshop can be kept around 55% without too much effort.

There are types of work I don’t like to perform in the dry room as it’s too far removed from actual conditions around here. Performing a acoustic guitar setup stablized at 45% and then sending the guitar back out to a customer’s home in the rainforest wouldn’t make much sense. Similarly, a guitar that’s lived a similar damp life for years should never be placed suddenly into a 45% rh environment, even though such is considered “ideal” for guitars…

I guess I’ll try to make one. It looks pretty handy.

You can even do it with one thermometer. Take the reading and write it down, then put a wrap a piece of wet cloth over the end, the water should be ambient temperature, and hold it over the inlet of you shop vac until it stabilizes. This will give you the wet dry readings. NOAA even has a online calculator. https://www.ready.noaa.gov/READYmoistcal.php

_________________
Jim Watts
http://jameswattsguitars.com

Even less Bob you absolutely can make this yourself and these units are no longer being manufactured, ours are surplus from ebay and the University stores here in Ann Arbor.

Two lab thermometers and your vac to draw air over them and a wet piece of cotton and you're golden.

So again any variation on the wet bulb test, sling psychrometers, Psychro-Dynes as pictured or two thermometers clamped to your bench with a vac will all get you to the same place.