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Leader Density: D-76 vs Rodinal and others


Thank you, Sal, for taking the discussion to the experts for their valued opinion. I never expected this thread to create such a firestorm of active discussion; I figured it had to be either pH (which has now been ruled out with many thanks to DD and SZ) or absorbed oxygen in the manufacturing process oxidizing the developer or just plain contamination. Foolish me, I thought a simple posting might dredge up someone with similar experience and we would put this issue to bed in an exchange or two.

I have long since dismissed the issue as my alternate water source is perfectly viable and now reliable. It was probably some inane shortcut in the manufacturing process of this particular brand of DW that introduced the problem. I have had zero issues since switching to filtered water.

Who knew it would take over a 100 posts to rule out my two perceived notions of possible problem areas! Anyway, thanks to all who contributed.
 
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Hate to wake up a sleeping thread but I thought it worthwhile to pass along further information. Last month, I absentmindedly mixed some D-76 with a gallon of distilled water I had in my storage cabinet. Not observing the knowledge gained in this thread I processed several rolls before I realized my mistake. Fortunately, I saved the rolls intact and hadn't cut them up and sleeved them so I had dates and leaders from the beginning rolls to the most recent. When I realized what I had done, I checked the density of the leaders with an exposure meter and the sun as a light source. The density of the leader of the first roll (FP4) was EV 9 and the last roll (processed 5 weeks after the mix date) had a leader density of EV 11.6, a full 2 2/3 stops less density than the beginning roll.

Yes, i know in a perfect world distilled water has virtually no buffering capacity (as mentioned by several of you) but Kroger distilled water is not manufactured in a perfect world and is not stored in a non-gas permeable plastic container.

Upon further research, I found steam iron manufacturers no longer recommend using distilled water in their irons as the distilled water absorbs enough CO2 to create strong enough Carbonic Acid to corrode the metal inside the iron. If the distilled water can corrode metal, it would certainly be strong enough to weaken the performance the D-76. In the couple of years since this post originated, I have used either tap water or bottled spring water with no observable loss in leader density when decanted and stored in filled/Saran sealed brown Boston rounds, within Kodak's recommended shelf life limits.

As an aside, the recent influx in cannabis growers, who use distilled water in their gardening, have to add a product called pH Up to restore distilled water to its design pH of 7. Apparently using DW with a pH in the 4-5 range causes their plants to not thrive and turn yellow.

Cheers!
 
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You are obviously not processing your film to the same degree of development in these two developers. It's that simple.
 
Petraio Prime said:
You are obviously not processing your film to the same degree of development in these two developers. It's that simple.
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And you have obviously not read the contents of the entire thread!! It's that simple!
 
Fred Aspen said:
And you have obviously not read the contents of the entire thread!! It's that simple!
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Yes, I did. You are getting different degrees of development, either due to the times not being accurate or some problem with the water.
 
As a trained chemist I can say that ONCE AND FOR ALL IT IS NOT THE WATER. Anyone that maintains otherwise does not understand the concepts of pH and buffer capacity. As to the argument that it is carbon dioxide dissolved in the water causing the difference let me say the solubility of carbon dioxide is not large and the resulting carbonic acid is a very weak acid incapable of causing what is observed.

Carbonic acid is such a weak acid that its acid salt sodium hydrogen carbonate (sodium bicarbonate or baking soda) produces an alkaline pH when dissolved in water.
 
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Petraio Prime said:
Yes, I did. You are getting different degrees of development, either due to the times not being accurate or some problem with the water.
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Or a problem with the developer temperature.

However as I said before that apparent density of the film leaders is dependent on the particle size of the silver. A fine grain developer like D-76 produces finer grain which appears more transparent.
 
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Jerry,
First off, I’m not going to engage in any arguments! That said, I have been using D-76 with either tap or spring water over the past three years and have developed many dozens of rolls of FP4 with leader densities equal to those of Rodinal and BT’s Two Bath with zero failures.

Then, using the same equipment (timer, thermometer (Kodak Process 3) and the same protocol), I used D-76 mistakenly mixed with a jug of Kroger distilled water. The first roll was fine; the last roll was a disaster. Again, the only variable in the equation was the water. My new batch of 76, mixed with spring water is just fine. Additionally, the 76 mixed with DW collapsed completely and was completely clear...not brown, a typical indication of oxidation.

I’m not arguing with you on the subject; I still believe the water is the culprit. I know, in theory, DW has no real buffering capacity. I absolutely agree to that, in principle. But, are you prepared to go out on a limb and say Kroger’s product is pristine, pure and has no real buffering capacity similar to lab grade DW?

So, if you still maintain that the water is not the issue, please, oh please, put all your expertise to work and tell me what I am doing wrong!!!

Again, no raised hackles here, I started this thread three years ago hoping to find the solution to the problem. In the end, after switching to an alternate source of water, I haven’t had one single failure in three years but simply mixing a batch of 76 with Kroger DW faithfully recreated the same sequence of failures, right down to the letter!

I am not a chemist; I am a retired EE so please put on your chemist's thinking cap and help me pinpoint the problem if it is not the water!

PS. I am/was a formally trained Shainin Journeyman and spent a huge part of my career traveling the world finding the ‘Red X’ and solving problems for large corporations far more complex than the simple situation described above. Google Dorian Shainin if you’re not familiar with the concept/training. So, if my training has failed me, please point out where I made a wrong turn in my problem solving! If not the water, pray tell, what is it?

Thank you.
 
Have you made sure that you're using enough developer when using D76 at 1+1?
The tech sheet for D76 also says:

If you use D-76 Developer diluted 1:1, dilute it just before you use it, and discard it after processing the batch of film. Before using the diluted developer, make certain that there are no air bubbles in the solution. If air is coming out of the solution and forming bubbles, let the solution stand until the bubbles dissipate. Don’t reuse or replenish the diluted solution. You can develop one 135-36 roll (80 square inches) in 473 mL (16 ounces) or two rolls together in 946 mL (one quart) of diluted developer. If you process one 135-36 roll in a 237 mL (8-ounce) tank or two 135-36 rolls in a 473 mL (16-ounce) tank, increase the development time by 10 percent (see the following tables).
 
I'm so glad you solved your problems, Fred!!! Happy shooting!
 
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