Does it need to be 68F?

krisb1981

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I was thinking about converting a trunk in my car into a small darkroom to process paper negatives as well as load them on the go. Since I would be carrying chemicals in bottles with no way to cool them, one questions arrises. Do the chemicals for processing BW paper need to be 68F for proper developing? or can they be 85F? I am thinking, since paper develops to competion in about 60-90 seconds, does higher temps affect anything else, contrast maybe?
 

Dkirk

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Not sure about contrast (I think it will increase - but if anyone can correct me please do) but with the higher the temp, the faster it will be developed.
 

cliveh

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85 is a bit high. I would suggest you try and keep within about 10 degrees above or below. Why not transport your chemicals in vacuum flasks?
 

jp498

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85 will work fine, just a little faster. It will oxidize faster if you don't keep it in a tight container when not in use.
 

Tom1956

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Calls to mind an old formula called Harold Harvey's Panthermic 777.
 

cheny03

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No need to be exactly 68F for paper, but 85F is a little too high.
 

DannL.

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I have developed paper negatives in the field by transferring the paper to a plastic print-drum inside a changing bag. Then I used chemistry that I had transported in a igloo cooler which contained a small amount of ice. That was fine then because it was in the middle of summer. I then rolled the drum by hand on the bed of the truck. I wasn't really concerned then as I am now about temperature. Now, I would probably transport two versions of chemicals, one in a ice filled cooler and another outside of the cooler. Then I'd mix the two in a container while measuring the temperature just prior to pouring into the drum. Afterward a quick water-rinse in the field was fine, followed up by giving them a good wash when I arrive at home.
 
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Axle

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Personally, I stick to 1-2 degrees plus or minus, and then keep same developing times without any real noticeable changes.

I aim to really to only have a 1 degree margin.
 

NedL

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Just out of curiosity, is the intention to then make contact prints in the field? Paper negatives store quite well after exposure for later development...
 
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krisb1981

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Reason behind me developing in the field is to see the results right then, rather than taking them home and developing there. Also if I shot a portrait of someone, I would like to give them the positive (yes, I plan to shoot positive paper) right then and there.
 

RalphLambrecht

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the speed of chemical reaction depends on temperature, but a time compensation similar to film development should help some. check Dr. Henry's 'Controls in B&WPhotography for some more details or conduct your own tests. remember that you will need a min time to dev full blacks. pulling a print prematurely will make for weak mid tones and shadows.
 

NB23

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Too hot it tends to bring out fog on the paper...
 

pentaxuser

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I seem to recall that when Nova Darkroom made( or probably more accurately had produced for them) a paper developer it had a scale of temperatures on the label that went up to 85F. Dev time at that temp was very short( probably 25-30 secs)

They no longer seem to make it but if I am right it means that it was perfectly possible to make a developer that operated at 85F

Ian Grant who spends a lot of his time in Turkey has to print at high temps. A post from him might help confirm whether 85F is OK

If there is no easy way to cool the developer then all you can do is try it at 85 in your darkroom to see if it works OK. If it does then you are good to go


Let us know the outcome


pentaxuser
 

Kawaiithulhu

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You may want to try using a more diluted mixture at your higher temperature. You need a development time long enough to give you some accuracy and precision, plus a more dilute solution will help tame the hot contrast you're likely to get from a short and very active cycle.

Also, longer times help even out development which is why we don't normally use super concentrated developers and zap paper/film at 120f for 10 seconds in the first place.
 

NedL

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Makes sense, especially with portraits
 

Bill Burk

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RalphLambrecht said:
|Iagree 65+-5 will be fine
Click to expand...

I agree. You're never too far from a bag of ice...

No matter what, since you are shooting direct positive... you will have immediate feedback on how well the process is going.
 
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