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  #1  
Old 4th July 2017, 06:04 PM
alexmuir alexmuir is offline
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Default Removing Thermometer bubbles

I've had several spirit thermometers over the years, most of which I've thrown out after they developed bubbles in the spirit. I had tried heating, freezing and shaking to cure them, but all without success.
Recently, there was a thread where thermometers were mentioned, and it was stated by another member that they should be stored vertically. I had never heard that before, despite taking Higher Physics and Chemistry at school, and a class entitled 'Basic Measurements' at college.
Anyway, I then arranged vertical storage for my most recent purchase, and the last one to contract a bubble. After a few days in that position, the bubble has gone. That is good, because that thermometer is longer, and more versatile than the replacement which is the Paterson certified model. It is too short to stand in a one litre jug.
Apologies that I cannot remember who gave the very useful advice about storage, but I thought it worth a mention that this could recover a thermometer affected by air bubbles.
Alex


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  #2  
Old 4th July 2017, 06:54 PM
Svend Svend is offline
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Great tip Alex -- thanks for posting that. I still use a mercury thermometer which I love, and I dread the day when it breaks as it has super-fast response and is easy to read...and it's long . I have a backup spirit one waiting so this tip may come in useful one day.
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Old 5th July 2017, 12:27 AM
M Stewart M Stewart is offline
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I have a Kodak Process Thermometer Type 3, mercury in glass. The instructions for correcting breaks in the capillary are :

"1. Heat a container of water (the water must be at least 9 cm, or 3 1/2 inches deep) to approximately 77 deg C (170 F).
2. Immerse the thermometer until the separations have moved into the expansion chamber.
3. Remove the thermometer immediately and allow it to cool in a vertical position."

Apart from the mention of the provision of a hole in the backplate allowing vertical storage, there's no recommendation to keep the thermometer stored vertically.

I'm pleased to report that my liquid in glass thermometers all agree as to what temperature my darkroom is. My digital thermometers choose to disagree, and that goes beyond their least significant digit - easier to read, but not reassuring.
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Old 8th July 2017, 12:18 PM
JOReynolds JOReynolds is offline
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I have a 1960s Gallenkamp mercury-in-glass thermometer in a wooden box with an NPL deviation certificate, which I keep as a reference. Mercury does not wet the glass, so horizontal storage is not required. Alcohol does wet the glass and so vertical storage works.
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  #5  
Old 1st November 2021, 03:39 PM
snusmumriken snusmumriken is offline
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I like a spirit thermometer because it's easy to read (wider column) and in my experience (sorry to disagree with Svend) faster to respond than mercury.

I think standing vertical may work for a spirit thermometer because of the wider column; but I don't believe it works for mercury, where the capillary is very fine. If it doesn't work, I can endorse the Kodak method posted above by M Stewart. I know this only from having made thermometers (both mercury and spirit) when at school. That is a practical class that is almost certainly banned nowadays!

The 77 deg C was evidently appropriate for the temperature range of a Kodak thermometer, and probably for most darkroom thermometers. [Why the very prescriptive 77 if it's only approximate? If your thermometer is bust, you can only be approximate anyway.] You must be careful not to boil spirit/alcohol, which happens very suddenly, and at best will create more breaks in the column. Obviously a (mercury?) thermometer with a scale reading up to 100 deg C will need a lot more heating to get the break in the column up to the expansion chamber.

The last time I had to rectify a break in the column was so long ago I can't remember when. I'm not clear how the bubbles arise in ordinary use, although physical shock can do it for mercury because of its inertia. FWIW, my thermometers do get stored vertically unless lying about on the bench or draining board between darkroom sessions.
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  #6  
Old 1st November 2021, 04:05 PM
Molli Molli is offline
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I have a couple of mercury thermomètres and find them impossible to read in the darkroom and I don't have any eye issues at all - not recommended, in my experience. Until a couple of years ago I used a spirit thermometer which more or less lived in my developer tray and I trusted that the stop and fix were at an equal temperature.

I now have a dial thermometer in the developer tray, kept seated in such a way that 20°C is in the 12 o'clock position and easily read even from the darkroom doorway by ambient light. No need to go in and fiddle around for my hard to access white light to see if the room's at a suitable temperature.
The thermometers not in use are sitting upright in a graduate and, despite one of them being in a wooden tube that looks as though it's been carved from the world's first tree, I've not had any problems with separation, nor with the spirit thermometer that has since been delegated to the fixer tray.

For those of you who are obviously far more knowledgeable than I, would you know why the person who sold me one of those thermometers told me off for pinching the tube between two fingers to get a reaction from it?
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Old 1st November 2021, 05:01 PM
Nat Polton Nat Polton is offline
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An old Meteorological Officer told me to put mercury thermometers in the freezer for a short while, then holding the thermometer at arms length, and the bulb away from you, swing the arm swiftly towards the floor and this should get rid of breaks in the mercury column.
It worked for me.
I use mercury thermometers all the time but do have a couple of spirit ones.
I shall store them upright in a jar in future.

Good tip.

Cheers.
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  #8  
Old 2nd November 2021, 01:06 PM
Terry S Terry S is offline
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Quote:
Originally Posted by Molli View Post
For those of you who are obviously far more knowledgeable than I, would you know why the person who sold me one of those thermometers told me off for pinching the tube between two fingers to get a reaction from it?
I've done this myself Molli, not knowing that I shouldn't (apparently...)

Anyone know the answer?

And after reading the full post, I had to google the following questions, which I found interesting...

1. How do you get a bubble out of a thermometer?

Heat the thermometer bulb under hot, running water. Don't heat it too long -- you don't want the mercury or alcohol to rise to the top of the expansion chamber. Once the bubbles are gone, hang the thermometer with the bulb down for several hours.

2. What is the blue liquid in a thermometer?

The science and development of non-mercury thermometers have made great improvements over the past few years. The blue spirit thermometers listed contain non-toxic isoamyl benzoate and dye. These thermometers can be stored horizontally; their separation rate is equal to or better than mercury thermometers.

Terry S
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  #9  
Old 2nd November 2021, 02:37 PM
Molli Molli is offline
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Hi Terry,
The gentleman who chided me with "Don't do that" was an old school pharmacist. For all I know, he was old enough to have been mixing potions, oops, prescriptions, from scratch back in the day.
I don't know if anything in that profile would suggest the reason for why he considered it a bad thing to do.
The oddest part is that I didn't ask him at the time, it stuck in my mind.... and I still never asked him in the decade that's since passed.

Now, of course, it's bugging me! Google was no help.
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  #10  
Old 2nd November 2021, 10:07 PM
Nat Polton Nat Polton is offline
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This talk of thermometers reminded me about a safety leaflet I read years ago.
It concerned broken mercury thermometers, and mercury spillages.
Apart from soaking up the spilt mercury with the correct medium, the bit that stuck in my mind was never use a vacuum cleaner to pick up spilt mercury.
Apparently the exhausted air from the cleaner will pump mercury vapours into the air and be breathed in by the operator.

Cheers.
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