Thermometer for Color Processing?

largeformat65

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Can anyone provide a suggestion on a good thermometer for use in color film development? I have been doing black and white for 30 years and just starting to explore doing my own E-6 at home. I know temperature control and accuracy is critical so I wanted to make sure I got a good thermometer.

Thanks
 

chriscrawfordphoto

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The Kodak Process Thermometer was the best. Accurate to 1/8 degree, but they're not made anymore, discontinued years ago because it was a mercury thermometer. Scientific supply companies still sell highly accurate mercury thermometers.
 

Gerald C Koch

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For several years when I was processing color reversal film I used an ordinary mercury lab thermometer. Never had any problem either with density or color balance.
 

Ken Nadvornick

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largeformat65 said:
Can anyone provide a suggestion on a good thermometer for use in color film development?
Click to expand...

Gerald mentions lab thermometers. Have a look at these affordable, general purpose, non-mercury lab therometers offered by ICL Calibration Laboratories, Inc. (Note that they are affordable because they are not formally calibrated and certified.)

Ken
 

Vonder

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I used to use a dial thermometer, a metal one with a long metal probe part and a dial for reading temp. Then I discovered it was 2 or so degrees out of calibration and went to using plain old floating darkroom thermometers. They work great but they are slowwww. I keep one in my water bath (A standard scientific lab water bath) and stick a clean one in the chem bottle to verify temp just before processing.
 

Gerald C Koch

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It's easy enough to calibrate a thermometer and save quite a few dollars. An ice-water mix is 0oC and once corrected for atmospheric pressure boiling water is 100oC. Various organic compounds can also be used. Certain compounds are better than others. The substance should be of reasonable purity and the molal freezing point depression constant must be small. A good choice would be naphthalene (one type of moth crystals) since it melts at 80.2oC and the constant is 6.9 oC/mole. The naphthalene would have to be very impure for the Mp to be significantly in error. Make sure to buy naphthalene and not paradichlorobenzene moth balls.

Melt the naphthalene making sure that it comes up to the immersion line of the thermometer. Then record the temperature as a function of time. The temperature will first drop as the naphthalene is allowed to cool. Then the temperature will level off as it begins to solidfy. Finally the temperature will again begin to drop when all the naphthalene has solidified. Now graph your results. The temperature for the middle of the straight line portion of the graph represents the freezing point 80.2oC.

When using melting/freezing points remember that both solid and liquid must be present for the result to be accurate.
 
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BMbikerider

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Absolute accuracy is not essential. What is essential is consistency. I am reasonably lucky to have a mercury thermometer which when bought was guaranteed to be accurate to within .25 of a degree. I also have a Kodak digital thermometer which didn't come with any guarantee of accuracy but when compared with the mercury one they read the same. I use the digital one in preference because it has a metal probe and responds to changes quicker than the glass mercury. It is also easier to use as well.

What I am trying to say here is buy a good thermometer and compare it with a certified one and note any difference. On the other hand there are so many variables that I don't think +/- 1 degree makes a terrific load of difference so long as you have consistency.
 

AgX

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A very cheap, high accuracy way would be using a digital clinical thermometer. Though, as their fluid-stem counterparts, they have a maximum-value duisplay. Handling such could become annoying.
 

ann

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I posted one of the Kodak classic ones a few weeks ago here on Apug. Asked a lot less than the one listed on ebay. If interested pm me.
 

amac212

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I have had great success with brand new DeltaTrak Auto-Cal Digital Pocket Probes. I have two of them (~$37 USD) and they're easy to come by. The read out is immediate and with an accuracy of + or - 1 degree Fahrenheit, they're perfect for C41 and E6.
 

Gerald C Koch

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BMbikerider said:
Absolute accuracy is not essential. What is essential is consistency..
Click to expand...

While this may be true for BW it is not true for color. Note Kodak's temperature requirements for their various color processes. They are quite restrictive if one wants good results.
 

wogster

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Gerald C Koch said:
For several years when I was processing color reversal film I used an ordinary mercury lab thermometer. Never had any problem either with density or color balance.
Click to expand...

The issue though isn't that your thermometer is within ⅛℉, it's that it's consistent. For example most glass thermometers have a fluid and a scale, the fluid expands as it's temperature raises, and contracts as it's temperature drops, the scale is then marked so that when the temperature is a certain point, the scale reads that point. If your scale says 100℉ and it's actually 100.5℉ that is okay, as long as the next time it reads 100℉ the temperature is actually 100.5℉. Your work flow will adapt to any shifts caused by the thermometer being a little off. Where it gets difficult, is if the next time you look at your thermometer and it says 100℉ it's actually 99.5℉ Because it's not consistent, your work flow can't adapt for any shifts, because the shifts are not consistent. Glass thermometers tend to always read the same, if they are off +.5℉ when new, then when you drop it and break it it will still be off +.5℉. The mechanical dial type were notorious for reading differently, some would read differently for different readings, some simply drifted as they aged. Digital ones can also drift as they age, the glass ones tended to remain accurate, but tended to get dropped after a while and break.
 

PKM-25

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Greg Davis said:
I use both a Kodak Process thermometer and a Paterson Color thermometer available from B&H for about $25. They match at the temperatures needed for color work, so I usually use the Paterson just in case I drop it, it is easily replaced.
Click to expand...

I had a Kodak one up until about two weeks ago. I got done using it, went to put it back into the 1 liter graduate that I typically stored it in and it slipped out of my hand and fell about 4" inches into the graduate and cracked.

I will never waste my money on one of those again, my cheaper dial ones all read the same as the fragile Kodak one anyway, just as fast and just as accurate...
 

Ken Nadvornick

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Keep in mind that some of the bi-metal dial thermometers have an adjustment nut on the backside of the dial casing. These can be very handy if you are standardized on a specific reference thermometer in your work. Or as you can imagine, they can also be a royal pain in the butt if they unknowingly fall out of calibration while being banged around.

The large dial Weston thermometers have these adjustment nuts. I found that mine would need to be checked and adjusted frequently enough that I just made it a regular part of my development routine. Eventually I got tired of that extra step, so I calibrated my inexpensive glass Kodak Darkroom Thermometer to 68F/20C* against my reference and now use that. It never goes out of calibration. But I do need to be more careful.

Ken

* 68F/20C on my reference thermometer registers as 69.6F/20.9C on my Kodak instrument.
 
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pukalo

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I bought a $10 digital cooking thermometer at Walmart, and have processed over E-6 100 rolls in the last 1.5 years using the Kodak, Tetenal, and Arista kits, with no problems. This, combined with a $3 styrofoam cooler with water overflow holes punched in the top has served me well for temp control.
As a side note, I suggest the Tetenal E-6 kit from Freestyle Photo, it gives much better results than the Arista. (Kodak kits being long gone...)
 

Roger Cole

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I bought and own two of those inexpensive digital thermometers. They disagree by more then three degrees, at least at black and white temperatures. The better one agrees to within less than 1/2 degree (about .3-.4) with my glass Patterson color thermometer, so I use that one.

Some of those are good but you must verify as some are also pretty far off.
 

John Weinland

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Digital thermometers can be found that are also NIST-traceable, meaning their absolute, not only relative values are accurate. Cooper makes their NIST-traceable DPS300, -58deg to +302deg F, or in Centigrade if you like, for about $35. The Cooper DPS300 cannot be fully immersed, just the sensor stem which is about 5" long and made of stainless steel. It has some more rather neat features.
 

ic-racer

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Your Kodak thermometer broke mounted in the metal support? I consider my Kodak thermometer to be my most durable because of the protective support.
 

mweintraub

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