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Increase Density on Second Run

Bob Carnie

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Here is a mystery.. A friend of mine is processing Pyrocat in Jobo in my Lab.

He is seeing more density every day in the first run , and the second run the negatives are less dense.

He is swearing that everything is done exactly the same.

I cannot give him a reason for this and I wonder if any of you have had this issue.
 

pdeeh

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fresh developer in each run you mean?
 

Lachlan Young

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Bob Carnie said:
yes fresh developer each run
Click to expand...

This may be a stupid question, obviously you're running single shot development, but is he mixing to working strength immediately before each run? My first thought was that he might be mixing all the developer he needs in one go, & pyro devs are not long lived once mixed to strength generally.

Also, is deionised/ similarly pure water being used?
 

bdial

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Not a problem I've encountered, but I don't often do repeat runs.

Is there any chance the drum has residual fixer? What is the clean up procedure at the end of the day vs between runs?
 

Ian Grant

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That would be my thoughts. although as long as the same water is used if two batches of fresh developer.

I do make up enough Pyrocat HD sometimes for 2 or 3 tanks but then these are staggered starts rather than consequence runs and I'm using older Jobo 2000 tanks and Paterson and they are inversion tanks.

As long as I use Pyrocat HD withing 10 minutes of mixing up there's no problem. However a lot depends on how fresh the metabisulphite was when the original Part A was made, this has an enormous effect on longevity. I've had Part A keep well for 4 years (no glycol).

Ian
 
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Bob Carnie

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Has anyone ever heard of a Jobo unit running slower in the first 10 minute , and speeding up over time??
 

MattKing

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Bob Carnie said:
Has anyone ever heard of a Jobo unit running slower in the first 10 minute , and speeding up over time??
Click to expand...
I don't know about a Jobo, but it occurs to me that if you are considering first thing in the morning, this describes me to a T.

Good luck solving the mystery.
 

TheFlyingCamera

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Mine seems to be very consistent with speed over time. It's not out of the realm of possibility that as the machine warms up, the speed of rotation changes - if anything, it would run slower to start then speed up as it warms up (lubricants get un-gummed). I'm more likely to believe that he's pre-mixing all his developer at one time, and the second batch is losing efficacy as it has had a half-hour to sit and oxidize. I always mix my Pyrocat HD one-shot, immediately before processing, just enough for the batch I'm about to run. It's a genius developer, but it goes bad FAST when mixed to working strength.
 
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Bob Carnie

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Hi Scott

He is absolutely not mixing two runs together , that I know for sure.
 

Marco Buonocore

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Ian Grant said:
I never shake any developer stock before use and that has never been an issue in 50 years of film or print processing. You want to make it oxidise faster ?

Ian
Click to expand...

I'm a stickler for following the instructions, and with the Pyrocat HD I get from the formulary, it says "shake well before use". I shake the hell out of it before I use it!
 
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Anon Ymous

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Marco Buonocore said:
I'm a stickler for following the instructions, and with the Pyrocat HD I get from the formulary, it says "shake well before use". I shake the hell our of it before I use it!
Click to expand...

I assume you need to shake part b which only contains carbonate at high concentration. AFAIK it is very soluble, but can be marginal if the temperature is low, leading to precipitate formation. I don't think part a would need to be shaken.
 

Photo Engineer

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This effect is described in Haist for some developers. When mixed fresh, they are more active and drop in activity with time. They then become stable. This is the origin of the old standby warning: "wait 24 hours before using a developer". This is for HQ and HQ like developing agents.

PE
 
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