Extreme Thermometer Dilemma

[Christiaan Phleger]

Hiya All,

So, here goes my dilemma, I'll spin quickly thru the old history.
Used to use Kodak Color Thermometers, broke my last 2 several years ago, then switched to Paterson Color, got 2 of them, they matched, used one sucessfully for 2-3 years. Finally got off my bum and got a Kodak Process Type 3, just had a chance to take one or two readings with my main Paterson Color and got a 'basically the same' reading, then broke that main Paterson Color. Pulled out my backup Paterson Color, and its 1/4 off the Kodak Type 3 but has a crack in the bulb at the base, so I'm not comfortable using it (especially since thats where the main one broke).

So, ordered 3, yep, Three brand new Paterson Color thermometers, all arrived safely, and yet, ALL are off compared to the Kodak Type 3!

Each are off 1 to 1 1/4 degree F at my usual temp range, 74-77. All 3 agree *with each other* by less than 1/4 degree F, but yet all are way way off the Kodak.

Now, I have this perplexing dilemma. I have a few years of notebook info about all my times and temps for films and chemistry, from Agfa in Acufine to Tmax in Xtol, lots of testing and sucessful processing of lots of film, and I certainly do not want to chuck all that good useful info. But, now I have 3 thermometers that are consistent, yet don't and won't match my reference thermometer no matter what.

I've tried putting all into hot water to raise them to max and then settle, several times, and then cold water to do the same, yet the results are the same. I don't want to continue to use the Kodak type 3 all the time since I am often klutzy and I'd rather clean up alcohol and dye than mercury.

While I was waiting for the new ones to arrive I did my usual film and developer in my usual temp range for the usual time, and the results are consistent with what I expect using the Kodak, so I know I'm still on the same general consistent thread of success.

So, do I use the new ones, adjusting and compensating for the 1 degree deviation? So then, change all my past data, where 5 min at 75F is now 5 min at 74F? What then happens where I pull something out of the notebook, say some of my frozen Agfa APX 25 in Rodinal, can I then trust my hard earned data from the past, just shifting over the temp?

Should I just chuck the three Patersons and start fresh with a new round of thermometers?

Going Round and Round in my head. Any and all Ideas will be considered and entertained, many and much thanks for the help in advance.

 

[Flotsam]

That is exactly why I use dial thermometers that can be calibrated. I use a Kodak Process thermometer as the control, calibrating all to it. I figure that will keep things consistent and requires only occasional minimal handling of the mercury thermometer, greatly reducing the risk of breaking it.

 

[Christiaan Phleger]

Hmm, good solution, I think I have one or two floating around. Still sticks with me the 3 thermometers, which I am now thinking I may just re-mark them with their own reference points.

 

[pentaxuser]

Are you sure that a 1 degree F difference really makes a noticeable difference? Maybe it's a little like accidentally extending a 10 min development time by 15 secs. Even a good darkroom person would be hard pressed to tell the difference in the neg and even harder pressed to contend that it made an absolute and irretrievable difference to the eventual print.

On my night school course the tutor used to say: " We don't worry about a 1 degree F difference when developing."

Just a thought

pentaxuser

 

[palewin]

Perhaps I'm missing something, but it would seem the solution is simple. You say all three are consistent with each other, and all three read one degree off your Kodak standard (I'm ignoring the 1/4 degree differences, which I think are too minor to worry about). So, for example, where the Kodak says 73F, your new thermometers say either 72F or 74F (you never specified whether the difference was high or low). Anyway, just take your existing data, adjust it for the new thermometers, and write it on a separate sheet of paper titled "new thermometer numbers." So, for example if your "N" development is 11 minutes at 72F on the Kodak, your "new" "N" is 11 min at 73F, assuming the new thermometers read one degree high.

 

[dslater]

Are you sure that a 1 degree F difference really makes a noticeable difference? Maybe it's a little like accidentally extending a 10 min development time by 15 secs. Even a good darkroom person would be hard pressed to tell the difference in the neg and even harder pressed to contend that it made an absolute and irretrievable difference to the eventual print.

On my night school course the tutor used to say: " We don't worry about a 1 degree F difference when developing."

Just a thought

pentaxuser

It makes a difference for color processes.

 

[pentaxuser]

It makes a difference for color processes.

I had based my reply on my assumption that the OP was talking about B&W developing based on the information he gave in his thread. In colour processing a 1 degree F difference may well make a difference but given how many people process colour effectively with different thermometers and simple water baths and use an averaging system which attempts to allow for drift I often wonder just how many even manage colour processing with up to a one degree F fluctuation.

Again just a thought

pentaxuser

 

[noseoil]

Use a 4% change per degree f for B&W processing. Only time I can think of a problem with B&W would be for a film like Efke 25 in a fast developer, otherwise the 4% difference is fairly slight. Since temps vary widely here in the desert, the 4% seems to be pretty good from 68f to 80f. You might try a "regular" processing with the different temp, just to see how it prints. tim

 

[Christiaan Phleger]

Thanks all.
The new 3 read low, so they read 74 when the reference KT3 is 75.
My times with my usual developer are around 6-7 min, and I usally add or subtract 40-50 sec per degree, allows me to process at 76 and 73 (real big temp shift out here!)
I run enough film that one whole whopping degree makes a difference in the rest of my workflow down the line. Sure, yeah, I know I can make it up on the printing but I've worked out the contrast, neg density and printing times to make the end product turn out how I like, want and intend. One degree, or 40-50 sec out of 6-7 min is too much shift for my palette.

After dwelling upon this, I've come to the conclusion that the scale on the three is mis-marked. From 60 to 135, all three are fanasticly precise, within 1/4 or even 1/5 off of each other, just exactly one degree off from the reference KT3.
Upon close examination of my old Paterson and one of the new ones, the scale is the same printing and distance between numbers, yet the thermometer is physically different (but close enough to think that they are the same). On the new version, the bulb shape is more narrow and longer by about 5mm, and the whole actual thermometer is shorter by you guessed it, 5mm. Looks like a manufacture error.

 

[noseoil]

Just a quick question, are you using this for B&W or for color? tim

 

[Christiaan Phleger]

B&W. It really is looking as if the scales have been printed from the wrong starting point. The new bulb is larger by 5mm in length and the whole shaft is shorted by 5mm yet the scale is printed in about the same spot, hence the 1 degree error.

 

[Roger Hicks]

B&W. It really is looking as if the scales have been printed from the wrong starting point. The new bulb is larger by 5mm in length and the whole shaft is shorted by 5mm yet the scale is printed in about the same spot, hence the 1 degree error.

How long do you give them to come to equilibrium? And what immersion depth?

 

[Christiaan Phleger]

At least 12-20 min, and 4-6 inches immersion, in same container. The rate of change is consistent, and over the whole scale is off by 1 degree, hot and cold, with the new 3 Patersons. The most logical explanation is that the printed scale is placed 1 degree too high.