How to glue back a hygrometer of an oblong case?

Edited: March 10, 2018, 11:38 AM · Hi,

the hygrometer that came with my oblong violin case was defective so I took it out. It was glued to the case. I bought a hygrometer (regular small round golden one) and I see all of them have this hole in the back plate.

Is this hole for the air to come inside the hygro?
If it is, then the one that came with my case, even if it wasn't defective, couldn't work.

This is the case:

How should I glue it to the case and what kind of glue should I use?

In case somebody tells me these hygros are more for decoration, I know, but right know the case has a very ugly hole there and also one of these is better than nothing.

Replies (19)

March 10, 2018, 11:40 AM · You could try some Velcro instead of glue as it would not be so troublesome to remove if you wanted to change it again amd it is also inexpensive.
March 10, 2018, 12:07 PM · I used fabric glue to glue the magnet that came with my humidifier to the bottom of my case. It work great! Some glues can melt fabrics/foam, ect so I’d use fabric glue.
March 10, 2018, 1:03 PM · But then how would the humidity of the air penetrate the hygro if I glue it and seal its only hole?

Indeed I don't even know how this design can work.

March 10, 2018, 2:13 PM · I'd stick a photo of you family or other favorite people over the hole in your case, and stow the hygrometer in the case pocket.
Edited: March 10, 2018, 5:30 PM · I agree with David about stowing the new hygrometer in the case pocket. But why not put the original hygrometer back in it's hole? Even though it doesn't work, it will still look right there. I'd bet that a huge percentage of the hygrometers built into violin cases don't work, at least not reliably. Join the club.
Edited: March 10, 2018, 5:56 PM · Why David?

I know these are not reliable, but at least you get an idea of the temperature and humidity, and I'd like a hygro right there at least working. The one that came doesn't move at all, it's broken.

I really want to glue it there. By the way, it took some minutes of pulling with care and see how it was going until I finally could get the original out, it was very well stuck there.

March 10, 2018, 9:09 PM · Hot-melt glue or urethane adhesive should do it. If that fails there is always duct tape.
March 11, 2018, 3:37 AM · "Why David?"

You may be able to glue the new hygrometer in successfully, but if you keep it in the case pocket instead, there is less chance of it coming loose and damaging the violin or bow, and will be easier to replace if it fails (and they do have a fairly high failure rate). In the case pocket, it should still give you a decent idea of the overall humidity in the case.

The hole you mentioned in the back is typically to allow adjustment of the reading by reaching in with a small screwdriver, but it would allow for increased air circulation as well.

March 11, 2018, 6:47 AM · Thank you David.

So, if you close that hole, the hygro won't work?

I mean, I guess it read the humidity by getting filled with air. Then if I glue it, I should not make a circle around it, instead I should draw lines or stripes going from the centre-out. That way there would be paths for the air to enter the hygro, right?

March 11, 2018, 10:11 AM · There are no other holes or vents in it?
Edited: March 12, 2018, 7:30 AM · It's pretty much identical to this one:

I didn't know that screw was to adjust it. I'd love to adjust it, and even if it's not that important since they are not reliable, I'd love to do it anyways for the sake of doing it and understanding the process.
Any guide?

March 12, 2018, 7:58 AM · On that one, it doesn't look there is a provision for externally adjusting the hygrometer.
March 12, 2018, 8:08 AM · I'd use the urethane glue. Either the usual foaming type (being very careful), or I see there is a non-foaming version that might be more appropriate for this job.
March 12, 2018, 11:06 AM · Isn't that a screw?

If you look at the pictures, there's one of the back plate where you can see what looks like a black screw with the - groove.

March 12, 2018, 2:15 PM · It may be a screw head, but it looks like it's positioned to adjust the thermometer, rather than the hygrometer.
March 12, 2018, 3:16 PM · Oh... can you show me what things hygros that are adjustable have so I can check if mine have them as well?
March 12, 2018, 7:16 PM · Answering as a cigar collector and I use a lot of those hygros :-)

That hole in the back is mainly to adjust the hygro needle with a screwdriver. It also allows for air circulation, but there are usually other air ways and even if there aren't, analog hygros are never airtight so even if you close the hole, it will equalize. Obviously, the less air circulation, the longer it will take. That will be noticed very particularly when at changing temperature, it gets condensation inside and the needle skyrockets.

Those cheap hygros never come right, so you are supposed to calibrate them. The normal DIY is the "method of the salt":

March 12, 2018, 7:29 PM · I own several of these hygrometers, and usually they are not air-tight as Carlos said. I never knew what this screw would do, since most of these hygrometers open (the stainless steel cover with the whole is usually removable and that way you can adjust the usually paper indicators without touching the needle which seems really sensitive) I second calibrating the hygros with the "salt" method as posted above

On one of my cases I have used the small whole in the back of the hygrometer as the necessary space to put a small screw and secure the back of the hygro on my violin case interior (of course in a plywood surface). Then the front gets in place "clip on" But I don't know if the hygro we are talking about works like that.

Anyway I would like to point out that some foam materials react with some glues in a not so pleasant way, so make sure to get the right one, a foam glue or something.

March 12, 2018, 8:06 PM · Wow, that was what I was looking for!
Thanks for all the replies.

Thank you.

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