Jobo Temperature Control

odell1618photography · Aug 26, 2019

View attachment 229715 View attachment 229716 I’m interested in processing c41 and printing RA4, I have a Jobo CPP2 and dichroic enlargers up to a Devere 8x10, so why not ? For some
Reason the temperature control aspect of C41 in the Jobo has given me doubts not actually knowing the actual processing temperature inside the tank.

So, from a kick starter campaign before I was told to never ever participate in a kick starter campaign ever again I had one of these sensor units from www.thepocketlab.com . I fished the temperature probe down the lift head and into the tank.

What I have found so far, is that if I set the water bath temp at 39.5 C , preheat the drum for 5 mins, add developer at 39.5 C and then dial the processing temperature down to 38 C my processing temperature for 3’ 15” is 38.8 C nominal.

With being able to monitor the temp during processing I’m sure I can tweak the water bath temperature to gain 38 C nominal.

I tried to attach my data in csv format but keep getting a file extension error.

mshchem · Aug 27, 2019

I've always been interested in just how much the temperature drops. My Darkroom can be cool in the winter. I don't get to worried with C-41. I know that we aren't supposed to pre wash, but I do, with copious amounts of tempered water. I develop for 3'30".

Years back I had a old laboratory, gravity convection oven. I would load a Paterson tank, and stick it in the oven let it warm for 15 minutes.
Used a bucket of sorts to maintain temperature during development, this was usually E6.

I may try your trick. I have some neat little digital aquarium thermometers, look similar.

ic-racer · Aug 27, 2019

I put some water in the drum, then, at the mid point of a simulated run, I open the lid and measure the temperature of the water with a standard thermometer. My temp readout on the Jobo shows the estimated in-tank temp, not the bath temp.

pentaxuser · Aug 27, 2019

OP from what you have said the developer which goes into the drum at 39.5 drops 0.7 C in the 3' 15" of the development time as long as you turn down the temp dial to 38. Interesting as I'd have assumed that the heat loss over 3' 15" would be less than 0.7. Presumably if you are developing more than one film in a session you have to turn up the water bath back to whatever reading on the dial gives you 39.5? I don't have a CPP2 but have a CPE so am I right in assuming the temperature controls only the water bath temp?

How easy is it to dial the water bath temp back up to 39.5 and how long does this take? Presumably only the same time as dialling the temp down so that in the time taken for the blix or bleach fix and washes the water bath has had plenty of time to rise back up to 39.5?

Thanks

pentaxuser

twelvetone12 · Aug 27, 2019

I've seen that there is a considerable temperature loss from the tempering bath and the process temperature inside the tank/bottles. On my machine I need to keep the bath temperature at 39C, and so the temperature inside the bottles will be 38C. I normally let the chemistry preheat for an hour or so with the bath, and normally with the 39C bath the process temp never exceeds 38 degrees.

Adrian Bacon · Aug 27, 2019

odell1618photography said:
View attachment 229715 View attachment 229716 I’m interested in processing c41 and printing RA4, I have a Jobo CPP2 and dichroic enlargers up to a Devere 8x10, so why not ? For some
Reason the temperature control aspect of C41 in the Jobo has given me doubts not actually knowing the actual processing temperature inside the tank.

So, from a kick starter campaign before I was told to never ever participate in a kick starter campaign ever again I had one of these sensor units from www.thepocketlab.com . I fished the temperature probe down the lift head and into the tank.

What I have found so far, is that if I set the water bath temp at 39.5 C , preheat the drum for 5 mins, add developer at 39.5 C and then dial the processing temperature down to 38 C my processing temperature for 3’ 15” is 38.8 C nominal.

With being able to monitor the temp during processing I’m sure I can tweak the water bath temperature to gain 38 C nominal.

I tried to attach my data in csv format but keep getting a file extension error.

On my jobo, I maintain 65F in the room the jobo is in, and set the water bath for 38.4C. I keep the developer in a separate bath set at 40.5C. I run the tank in the main bath for 3:15 as a preheat, then put the developer in and run it. After 60 seconds, I sample the temperature of the solution at the mouth of the tank and it’s right at 38C. At the end of 3:15, it’s wavering between 37.6 and 37.7

odell1618photography · Aug 27, 2019

pentaxuser said:
OP from what you have said the developer which goes into the drum at 39.5 drops 0.7 C in the 3' 15" of the development time as long as you turn down the temp dial to 38. Interesting as I'd have assumed that the heat loss over 3' 15" would be less than 0.7. Presumably if you are developing more than one film in a session you have to turn up the water bath back to whatever reading on the dial gives you 39.5? I don't have a CPP2 but have a CPE so am I right in assuming the temperature controls only the water bath temp?

How easy is it to dial the water bath temp back up to 39.5 and how long does this take? Presumably only the same time as dialling the temp down so that in the time taken for the blix or bleach fix and washes the water bath has had plenty of time to rise back up to 39.5?

Thanks

pentaxuser[/QU. Correct, If I don't dial the water bath temp down the drum temp starts to increase. I made another run last night, my drum temp dropped down to 38.2 C within 5 seconds and maintained 38.2 C for the 3' 15" development time.
It seems that at two hours after the initial startup temps are more consistent.

I'll upload a CSV file if I can.

Thanks,
Charles

odell1618photography · Aug 27, 2019

pentaxuser said:
OP from what you have said the developer which goes into the drum at 39.5 drops 0.7 C in the 3' 15" of the development time as long as you turn down the temp dial to 38. Interesting as I'd have assumed that the heat loss over 3' 15" would be less than 0.7. Presumably if you are developing more than one film in a session you have to turn up the water bath back to whatever reading on the dial gives you 39.5? I don't have a CPP2 but have a CPE so am I right in assuming the temperature controls only the water bath temp?

How easy is it to dial the water bath temp back up to 39.5 and how long does this take? Presumably only the same time as dialling the temp down so that in the time taken for the blix or bleach fix and washes the water bath has had plenty of time to rise back up to 39.5?

Thanks

pentaxuser

To be more concise, the drum temp drops 0.7 C withing a few seconds, and remains consistent at 38.8 C for the remainder of the 3' 15" development time.
My last run last night the drum temp dropped to 38.2C within a few seconds and remained consistent at 38.2 C for 3' 15" C. I did turn the waterbath temp down 38 C at the
start of development from 39.5 C

odell1618photography · Aug 27, 2019

What I am sharing here is a method of monitoring the temperature inside the drum during processing.
The sensor connects to a smart phone and displays the data on a graph over time that you can also record to a CSV file.

The only tricky aspect is feeding the temp probe down the inlet to the drum. I used a piece of string,
washing the string down the inlet with water until it floated out into the water bath, then tied the
string to the probe and pulled it through.

pentaxuser · Aug 27, 2019

OP Thanks for the reply.

pentaxuser

mshchem · Aug 27, 2019

odell1618photography said:
What I am sharing here is a method of monitoring the temperature inside the drum during processing.
The sensor connects to a smart phone and displays the data on a graph over time that you can also record to a CSV file.

The only tricky aspect is feeding the temp probe down the inlet to the drum. I used a piece of string,
washing the string down the inlet with water until it floated out into the water bath, then tied the
string to the probe and pulled it through.

Cool, where do I get one of these.

odell1618photography · Aug 27, 2019

mshchem said:
Cool, where do I get one of these.[/QUOTE

www.thepocketlab.com

Pocket Lab Weather is what I have.
Check out the images in my first post.
The attachments are corrupted, I'll post new images later.

odell1618photography · Aug 27, 2019

odell1618photography · Aug 27, 2019

Those are images of my setup, temperature probe, Pocket Weather, Water bath settings at begin and water bath settings at end.
The Temp on the Digital Readout of the Jobo at begining is 39.5 C, the knobs are set at 39 C, the display fickered between 39.5 C and 40 C.
My recorded water bath temp was 40.09 C at end of two hour warm up.
I started my prewarm at 43", drum temp 29.98 C. The drum and reel came off the shelf and were at ambient temp of 27.1 C
I started my development at 395", drum temp 31.8" and turned water bath settings down to 38 C
at 410", drum temp 37.92 C
I ended development at 590", drum temp 38.06"
I started bleach at 600", drum temp 38.92 C
I ended bleach at 994 ", drum temp 38.35 C
Then six washes at 30" each +-
I started Fix at 1172", drum temp 37.78 C
I ended Fix at 1525, drum temp 37.78 C
Attached is a pdf of the data and a zip file in csv format.

odell1618photography · Aug 27, 2019

Any comments, suggestions or observations to my process are welcome and desired.

RalphLambrecht · Aug 27, 2019

odell1618photography said:
View attachment 229715 View attachment 229716 I’m interested in processing c41 and printing RA4, I have a Jobo CPP2 and dichroic enlargers up to a Devere 8x10, so why not ? For some
Reason the temperature control aspect of C41 in the Jobo has given me doubts not actually knowing the actual processing temperature inside the tank.

So, from a kick starter campaign before I was told to never ever participate in a kick starter campaign ever again I had one of these sensor units from www.thepocketlab.com . I fished the temperature probe down the lift head and into the tank.

What I have found so far, is that if I set the water bath temp at 39.5 C , preheat the drum for 5 mins, add developer at 39.5 C and then dial the processing temperature down to 38 C my processing temperature for 3’ 15” is 38.8 C nominal.

With being able to monitor the temp during processing I’m sure I can tweak the water bath temperature to gain 38 C nominal.

I tried to attach my data in csv format but keep getting a file extension error.

that's a neat little device.

dkonigs · Dec 20, 2019

I know this is an old thread, but I figured I might as well share my own experiences on the subject.
John Tinsley's book "The Rotary Processor Manual" recommends setting the water bath to 39.8°C to deal with this issue (which isn't far from what's been tried above).
I'm personally using a CPP-3, whose control panel (at least in auto-mode) doesn't let you fiddle with the bath temperature mid-process, however I wouldn't expect such fiddling to have a fast effect anyways.

So what I've been doing for C-41 is to set the "process temperature" (i.e. the water bath temperature) to 39.8°C. I then stick a thermometer into the developer bottle, and start processing as soon as it reads 38°C.
The first film I did this way was a C-41 process control strip, which I then dried and inspected on my densitometer. Its numbers were pretty much bang-on when compared to the reference (or close enough, within the instrument's margin of error). Regardless, it was significantly better than I ever got using a Sous Vide and inversion tanks previously.
I've since done a few actual rolls of film following the same approach, and haven't had any complaints about the results.

barzune · Dec 21, 2019

dkonigs said:
.....John Tinsley's book "The Rotary Processor Manual" recommends.....

I've never heard of that book. Can you recommend it for a newby (to JOBO equipment)?

dkonigs · Dec 21, 2019

barzune said:
I've never heard of that book. Can you recommend it for a newby (to JOBO equipment)?

Honestly, its hard to say. It actually doesn't provide much of any useful "manual-type" how to information. As a newbie to Jobo equipment myself, I had a lot of nitpicky questions I had to answer elsewhere. (And I'm planning to eventually put some of this into a video, as a companion to the unboxing/setup videos I've already made.)

What the book does provide is a lot of processing recipes (that can be found elsewhere) and the occasional useful factoid (like what I've shared) buried among its pages.

Basically, it can't hurt to have this book handy. But if you're trying to justify the cost of buying it, then it probably isn't worth it.

odell1618photography · Dec 21, 2019

ic-racer said:
I put some water in the drum, then, at the mid point of a simulated run, I open the lid and measure the temperature of the water with a standard thermometer. My temp readout on the Jobo shows the estimated in-tank temp, not the bath temp.

I insert the probe into the drum and get live temperature readings during the development, I’m not measuring the water bath temperature. I ran the probe from the top of the lift through the chemistry port down and through and out the outlet.

By being able to monitor the temperature inside the drum during development I’ve been able to establish a development temp of 38 C plus or minus 0.1 consistently.

barzune · Dec 21, 2019

dkonigs said:
Honestly, its hard to say. It actually doesn't provide much of any useful "manual-type" how to information. As a newbie to Jobo equipment myself, I had a lot of nitpicky questions I had to answer elsewhere. (And I'm planning to eventually put some of this into a video, as a companion to the unboxing/setup videos I've already made.)

What the book does provide is a lot of processing recipes (that can be found elsewhere) and the occasional useful factoid (like what I've shared) buried among its pages.

Basically, it can't hurt to have this book handy. But if you're trying to justify the cost of buying it, then it probably isn't worth it.

Good to have your view, and thanks for the feedback.
I'll try my machine out, and see whether I understand what I'm doing. Good to know though, that there is another reference available.
Always grateful for advice.

mshchem · Dec 21, 2019

Do the same thing every time. If you shoot chrome, adjust 1st developer time until you hit the box speed or if you have control strips they are dead on. To be repeatable with a Jobo ambient temperature is a huge factor. The volume of chemistry is a factor. I use a 1520&1530 tank combination even if I am only developing 1 roll of film, to use as much warm chemistry as I can.
With reversal film I pre wash a few times to insure tank and lift are at as close to target temperature as can be.

With negative film you can get away with a little variation, but slides are unforgiving, that's what makes it so fun

PS buy a used Jobo tempering box to go with the processor

Steven Lee · Feb 6, 2023

I just discovered this thread, and it's been great. Sorry for bumping it, but I think I have useful data to contribute for those who're looking for tricks to achieve consistency and accuracy with a JOBO.

Here's my process:

- Always use 500ml chemistry in the JOBO 1540 tank with two 120 reels or four 135 reels.
- A water bucket with a sous vide is set to 101F for warming chemicals in 500ml bottles.
- Ambient is within 67-69F range.
- The tank is loaded with film sits in the bucket submerged to 2/3 of its length, DRY for 10 minutes. Dumbbell on top.
- Then I submerge the tank completely into 101F water for one additional minute.
- JOBO water bath is exactly 39C - that's the actual water temperature

Now the numbers:

- Right before pouring the developer into the tank, its temperature is 101F
- Immediately after pouring the temperature inside the tank is 100.3F (-0.7F drop)
- Temperature after 3:15 in the JOBO is 100.3F, so it's completely stable

Other numbers: 500ml of chemistry heated to 101F in a plastic bottle sitting on a countertop loses 0.1F every six seconds with an open lid. This is helpful when you're pulling the developer bottle out of a souse vide bath and it's hotter than 101F. I just count the required number of seconds while holding it in the air.

This procedure allows me to keep the entire process consistent and within 0.2F. Never had the luxury to run a control strip though, but loving my results. Anecdotally, before I dialed everything in, I observed color shifts at higher than 100F runs. Fujifilm stocks are more temperature sensitive than Kodak, especially the Superia (magenta becomes a concern).

MattKing · Feb 6, 2023

Steven Lee said:
Sorry for bumping it

Hey - we like it when people revive a useful and informative thread to add some more useful and informative contributions.
Just don't bump an old thread to revive any arguments

ic-racer · Feb 6, 2023

Not sure in re-reading this thread if people understand how the Jobo works. Over one hour warmup is needed. The temp one sets on the knobs is the processing temp. The water bath temp is about one half degree centigrade higher if the Jobo is functioning correctly. This is all in the manual.

For example Page 25:

The temperature of the actual process (inside the tank or drum) is equal to the temperature stabilized in the bottles or graduates, not the temperature of the trough or post-processing effluent.

Jobo Temperature Control

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