Humidifier effectiveness.

What kind of difference should I expect between the relative humidity of a room and a uke case with a humidifier in it?

I've been experimenting with a humidifier in an empty case because my current room hygrometer won't fit in the body of the case with the uke in there. I've done the salt test on the hygrometer over 2-3 days and it is right on +/- 1. For the humidifier, I used a 4 oz rectangular prescription bottle (like you get at Target) filled with hydrated gel beads. A couple dozen small holes (3/32") were drilled on the exposed flat side of the bottle. The hygrometer was placed in the main body of the case.

When I placed the humidifier in the head space of the case, the humidity only rose 1 or 2 points. When I placed the humidifier on top of the little accessory case where the neck of the uke would be, the humidity rose 5-6 points. I then added a regular sized prescription bottle with a wet sponge inside it. (approx. 6/16" hole in cap and bottom) and the readings have been the same so far. The added humidifier didn't add to the 5-6 points.

Is a 5-6 point difference in the case humidity from room humidity typical? Low? What should I be doing differently if anything? The case I'm using is one of those hard, styrofoam-core cases covered in that canvas like material which zips closed.

From what I remember from chemistry class, you should expect a given humidifier in a volume of air at a given temperature to create a given humidity, independently of the starting RH of the air. (assuming the air is dry to begin with)

IOW a humidifier should get you to a given range of interior humidity regardless of the outside conditions. Unless the case is porous.

But that class was a long time ago. I wouldn't worry too much. I put a toothpick case with holes and a sponge between my strings in the case, where it will do the most good.

I guess what I'm asking is, how much difference can one reasonably expect from a case humidifier? I'm guessing if the relative humidity is 25-30%, you're probably not going to get your case up to 45-50%.

The case will absorb humidity so it may take a few days (and refills of the humidifier) to see the reading rise much I think. Also, the fabric is porous and the zipper allows humidity to escape. If you have the humidifier at one end and the hygrometer at the other you will see less response. I use two film canisters with a few small holes and sponge inside, one at each end of the case. Like you, I'm in the frozen north and with full on central heating last winter I was able to maintain 45% and I'm sure the room was in the low 30's at best.

You might also try putting your humidifier and hygrometer in a plastic bag and just see how it responds.

I've come to the conclusion that it's pretty difficult to over humidify but pretty easy to under humidify. So... I do it this way. I have three humidifiers in my concert and tenor cases... two in the main case and one hung on the strings inside the bouts. Works well... not too much not too little. Anytime I open the cases, regardless of the weather outside... I'm always at about 48%. I have two in my soprano case... one in the case and the other hung on the strings. About the same results as the concerts. Hope this helps.

I completely agree with original poster, Mike, plus the wisdom of those that replied here, based on my personal experience. Little change from a half-cigar sized sponge of tapwater. Very little. So, why use it? For travel only.

What do I do otherwise? Ukes in Steri-lite underbed boxes with car wash sponges in gallon ziplocks. Period. How much change in humidity--oh, twenty to thirty points. Regulate with opening the top.

http://www.ukuleleunderground.com/f...-Extremely-Effective-(too-effective-)-Humidor!
Here's a thread about it (with photos on post#14)

So, yes, as peewee says, from old chemistry class plus physics, there's no way a device with 2 ounces of water in it is going to make a big, or a prolonged, change in humidity in a large, felt-lined case. It will, over time, stink up the case pretty good with micro-mold, if that's the goal, though. LOL