Instrument humidifier test

[almeriastrings]

A recent thread on instruments in low humidity regions prompted me to run a short test. I will do some further tests over the next week or two. We live in a very low humidity, very hot, environment - bordering on Europe's only 'true' desert, in fact where the Clint Eastwood "Fist Full of Dollars" movies were all filmed.

Yesterday, at noon, this is what it was like out there:



Humidity under 10%, and air temperature 34.2 Celsius, 94 Fahrenheit. It gets considerably worse than this in July and August...

Inside, I placed a mandolin in its case in a room with no AC running. These were the conditions:



RH 17.8% and temperature 26.7 Celsius, 80 Fahrenheit.

I have been using the DAMPIT humidifiers for quite some time, but had no real data on how well they worked. I normally use a Viola model for my mandolins. I added a Dampit here, and also included a miniature temperature and humidity data logger, set to record every 60 seconds, positioned inside the instrument under the opposite 'F' hole from the Dampit.

The blue line is temperature.
The red line RH.
The green line is the dew point.



The results seem to show that the Dampit works pretty well, keeping the humidity well within 40-50%, averaging around 45%, despite external humidity dropping below 18%.

I used a fibreglass case here, with quite an effective rubber seal. I will repeat this test with a wooden case to see what effect that has. I'm also going to try a different case humidifier...

[Tavy]

Interesting, and good to see some real data. Do you place the Dampit actually in the instrument? I wonder how well it would work if it was merely elsewhere in the case (in which case it would eliminate the possibility of water spills)?

[almeriastrings]

Yes, I used the Dampit as directed. Essentially, you soak them briefly (in distilled water to avoid calcium build-up), then squeeze out all excess (I use a paper towel). This is very important, as if used too wet you will get leakage and possibly damage. I have used them for years like this with no problems, however. As to how it would work elsewhere, I think that would depend on the case design and airflow between sections. In some cases, I suspect that is pretty minimal. Used as directed, they do deliver the humidity right where needed, and in the most vulnerable areas to cracking. I have a few more tests to run. I am going to place multiple recorders both in and outside the case, for example, to get simultaneous readings from several areas.

[Folkmusician.com]

This is a great idea for a test. Of course you had to go and rekindle my desire for a Fluke!

[Jeff May]

Yes, I used the Dampit as directed. Essentially, you soak them briefly (in distilled water to avoid calcium build-up), then squeeze out all excess (I use a paper towel). This is very important, as if used too wet you will get leakage and possibly damage. I have used them for years like this with no problems, however. As to how it would work elsewhere, I think that would depend on the case design and airflow between sections. In some cases, I suspect that is pretty minimal. Used as directed, they do deliver the humidity right where needed, and in the most vulnerable areas to cracking. I have a few more tests to run. I am going to place multiple recorders both in and outside the case, for example, to get simultaneous readings from several areas.

I've used the Dampit in the past, but was always concerned about leakage and was never really sure how frequently it needed to be re-soaked. No doubt they do put the humidity right where you want it though.

It's fairly dry where I live and I now use an Oasis humidifier. I like it mainly because it holds a good bit of water you know when it shrivels up you need to refill it. I use one in all my hard cases and also a Gator soft case (not a gig bag, the one like a Travelite). I keep a portable cheapo hygrometer in the soft case and it stays between 40 and 50%. I sit in my truck and play on my lunch hour sometimes and when the case is propped open the hygrometer reading will drop down to 18%. Put the mando back in the case and close it up; less than an hour later it will be back up to 40%+. The humidity stays about the same in whatever kind of case I've used. It would be interesting to know if the rubber sealed fiberglass cases reach higher RH levels. I've considered getting one for just that purpose; for the ultra dry conditions in my house during the winter with the wood stove going.

[herbsandspices]

This is awesome - thanks for your hard work and awesome chart!

It would be interesting to compare it with a test of the humidity outside of the case, and one inside the case without a humidifier - both over the same time frame.

[almeriastrings]

That is exactly what I plan to do this week. Should have the results soon.

I am also going to directly compare results in a fiberglass case vs. a traditional wooden case.

[almeriastrings]

This is awesome - thanks for your hard work and awesome chart!

It would be interesting to compare it with a test of the humidity outside of the case, and one inside the case without a humidifier - both over the same time frame.

Here you go:

EXTERNAL



Max RH 39.23%
Min RH: 28.41%
Deviation: 10.82

INTERNAL



Max RH: 52.04%
Min RH: 50.78%
Deviation: 5.04

As far as Dampit's go, I think I..um... rest my case

Will repeat with some traditional wooden cases and see what happens there.

[almeriastrings]

This speaks for itself... if you use a Travelite case - don't trust that hygrometer! I tested 4 of them, and not one was even close. They consistently over-read by 8-10% under all conditions, even worse in some instances. That thing must be there more for looks than anything.... the problem is that it is worse than useless, as it gives a false sense of security.



Here's a true RH of 26.9% - with the case hygrometer claiming 40%.



Other examples







At no point, even with humidities as low as 25%, did the case hygrometers drop below 40%. That is really quite shocking. If you do use one of these cases, I would ignore the hygrometers completely as they are entirely misleading.

[herbsandspices]

WOW, this thread is really great!
Finally someone quantifying all of these methods.
Thanks for all of your hard work!

[almeriastrings]

A new test, this time in the left corner, we have a typical "in Case" humidifier, from Herco. One immediate problem with these is getting them where they are most effective. Near the headstock or in the accessory compartment produces very poor results as the zone of humidity tends to stay "trapped" in that area. To remove that effect here, I used two 'A' model mandolins and positioned the Herco in the space available. Obviously, this would not be very practical if you are moving the case around or for an 'F' model:



In the right corner, we have a Dampit viola humidifier. In both cases, data was recorded from inside the mandolin body, under the lower 'F' hole. External humidity was quite low:



To add another dimension, I wanted to see how well the humidity in the case recovered after a 5 minute opening. Both cases were therefore opened for that period at 2.00 pm. You can see the sudden plunge, followed by recovery as the case is closed again.

The results. Herco first:



Dampit:



The Dampit was far more efficient at getting humidity into the instrument than was the Herco, which barely exceeded 40% RH. The Dampit maintained humidity at an average of 54%. Both humidifiers allowed recovery after the case was opened and low humidity air was introduced. These results suggest that in very low (<35%) humidity conditions, the Dampit-style of instrument humidifer is the clear winner. The in-case Herco type has some effect, but it is much more limited, even if it can be positioned optimally. Positioned in the headstock area or accessory compartment, the effect of this type of humidifier is absolutely minimal and should not be relied on.

[pjlama]

Wow, now I need to order some dampits. The only thing that scares me about them is making sure they don't leak inside the instrument. I'm pretty sure that would not be good.

[almeriastrings]

Yes. That is the danger. However, I have found the following method works very well and I have seen no evidence of damage where this procedure is followed:

1) Hydrate using distilled water only. City water may contain high levels of mineral residues.

2) Squeeze out well, then follow by repeating the squeeze between paper kitchen towels.

3) Allow to 'air' for 5 minutes before placing inside instrument.

If you put them in too wet, then yes, damage will occur.

Depending on where you are, and what the ambient humidity is like (also on the case seal) you may need to re-charge every 48 hours or so.