A large bubble in my thermometer...

Hi

I was about to process a few TRI-Xs and I just encountered the following problem.

The bath temps read by my precision thermometer are all false, by about 10

degrees F., because there is large bubble (or a "no-alcohol" area) in the

thermometer column. I, unsuccessfully,tried to put it in the freezer to "burst"

the bubble. What shall I do? Buy another one? (Like a super-precise digital one,

hint hint).

Thanks!

I hear you! I got a "deal" on a card of five brand new Kodak "color" darkroom

thermometers. But they had been lying on their side for decades. Totally broken up.

 

Nothing I tried worked. By sheer luck, the local University had some dry ice. I placed it

between two chunks and eventually the parts merged at the bottom. I think I was lucky not

to have broken it. Don't know for sure.

 

So, can you get some dry ice?

Chill the thermometer in ice water until the thread is at the calibration mark (or as low as it will go). Then hold the thermometer at the top and tap or flick the stem with a fingernail. You can usually rejoin the thread in a short time.

 

You don't need dry ice, and alcohol gets pretty viscious at dry ice temperatures anyway. Dry ice alone has very poor heat transfer. If you need to chill something to -100F, use alcohol (denatured or isopropyl) mixed with chipped dry ice as an heat transfer medium.

I have fixed lab thermometer several times by heating. Heat with the bulb gently touching a hot plate. Carefully watch it as the liquid goes up into the small bulb at the top of the column. Heat until you have an unbroken column of liquid from the bulb at the bottom to the bulb at the top, and then remove the heat. The liquid should retreat in an unbroken column.

 

I one was able to fix a thermometer with about 6 bubbles using this method.

If you decide to use heat, do it very slowly. I speak from experience, having popped the end off one recently.

Liquid-in-glass thermometers almost never lose their calibration. Overheating the bulb is the only assignable cause I've encountered. In short, use ice water.

I use an old Patterson thermo, but recently bought a cheap, $15 digital thermometer for cooking. It is spot on accurate and one of the best uses of $15 I've had in a long while.

Hm... had the same problem, tried refrigerator, hot water, and only 2 of the 6 bubbles disappeared. Will try ice water to see if helps.

I recently fixed 1 by putting it upright in the freezer for a day.

 

I have since gone digital...with my thermometers... not my cameras.

 

Larry

Hold the thermometer vertically with the reservoir down and tap it near the gaps with a plastic stirring rod. My big 'ole Kodak thermometer was set to right in a few minutes. I wouldn't try heating it but cooling may help.

 

Cheers,

Well, I solved my problem last night. Put my thermometer in water in refrigerator until the water turned ice, than I boiled another water recipient and changed the thermometer back and forth in each recipient 3 times I think. 4 Bubbles dissolved.

Hey thanks a lot for all the replies/suggestions, etc. I got rid of the annoying bubbles by putting my therm in warm water (like 110?F.). Worked much better than I thought, it works like a new one but I still got the "go-digital" voice in my head... :-)

I'm glad you got your problem resolved, but hold on a minute before you go out and spend big bux on a digital thremometer. A couple of years ago I was thinking along the same lines as you are now and bought a fairly expensive one. After a couple of months the thing up and quit working. Next stop - WALMART! Went into the housewares section and bought a digital kitchen thermometer. You know the kind that you stick into a roast to check its internal temperature? Spent less than $15 on the thing. It is still working and is plenty accurate enough for darkroom work, be it B&W or color. Checking it against my Paterson Color Thermometer shows a descrepancy of less than 1/2 of 1 degree F., and it is consistent. What more could you ask for?

What you did was right, Fred

 

You just didn't do it long enough. I've done this for 40 or 50 years. You put liquid column thermometers in the deep freeze for several hours and then put it into room temperature to stabilize. I've never seen it fail.

 

Lynn