Why not 2 baths developer only?

[Raghu Kuvempunagar]

FWIW, 2 bath development would seem to be impractical for anything like a high volume commercial line.
And many/most of the commercially packaged developers are oriented toward that sort of environment, even if that sort of environment has become rare.

Interestingly, two-bath developers were found to have certain advantages over conventional developers when it is necessary to get "a more uniform degree of development throughout the life of a developer" as would be the case in motion film processing.

 

[Raghu Kuvempunagar]

I believe Photo Engineer disclosed here the secret ingredient X in Microdot-X shortly before he passed and went to the big yellow R&D lab in the sky.

And nobody seems to have followed up the idea subsequently in contrast to the copious interest the subject generated prior to the disclosure.

 

[snusmumriken]

What is the preferred method for changing from bath A to B?

• Pour A out, then B in.
• Or: lift spiral from tank (lights out, obviously) and lower into second tank with B solution

For me, the first of these. The second is way too complicated. I use Paterson tanks, in which filling/emptying is very fast. But the main thing is that you always do the same, and tweak your timing if you don’t get the results you want.

Diafine instructions say: 'Because Diafine has the property of limiting highlight development, increased exposures result in higher shadow densities without "highlight blocking", thus effectively extending the tonal range. Diafine can accommodate as much as a two stop increase over the recommended indexes, without serious loss of quality." The recommended film E.I.s from the Diafine instructions are higher than box speed. For Tri-X 400 it is E.I. 1600. Why would they recommend those E.I.s if film lost speed with Diafine?

This doesn’t make sense. Increased exposures (first sentence) means decreasing EI, not increasing EI (second sentence).

 

[MattKing]

Interestingly, two-bath developers were found to have certain advantages over conventional developers when it is necessary to get "a more uniform degree of development throughout the life of a developer" as would be the case in motion film processing.

View attachment 405469

I could certainly see how two bath developer modifications could be applied for motion picture film development - those long reels of film run in high volumes through the machines.
But commercial labs that develop many short rolls of film - that would be more of a challenge.
Unless the labs were able to approach them the same way as Kodachrome - many customer rolls, all spliced together into a long single roll, run through the machines, and then separated at the end back into single rolls.

 

[Milpool]

Salt is in there but the secret ingredient in Microdol-X was Chlororesorcinol according to Ron Mowrey (from a conversation with Richard Henn). Henn had worked on this at Kodak in the 50s/early 60s in an effort to find additives to extra fine grain developers that would prevent problems like dichroic fog on emulsions in those days. The two Henn/Kodak patents are online.

I'd be interested in hearing your formula for "home brew" Perceptol. I once tried a formula based on the standard D-23 formula + kosher salt, and reducing the metol to 5g instead of 7.5g. It was supposedly a Microdol "home brew". In actuality, the grain was NOT Microdol grain. The secret ingredients to Microdol X have never been revealed as far as I know. but kosher salt ain't it. thank you.

 

[bernard_L]

For me, the first of these. The second is way too complicated. I use Paterson tanks, in which filling/emptying is very fast. But the main thing is that you always do the same, and tweak your timing if you don’t get the results you want.

Thank you @snusmumriken. I also use Paterson tanks, so...
In the meantime, I found this post from 2013 by @David Allen

Roll Film AGITATION - Thornton's Two Bath

I have been working with Thorton's Two Bath Developer (120 roll film on stainless reels) for the past couple of months. I have had excellent luck so far and am settling into an agitation pattern. I have The Edge of Darkness and have done quite a bit of "web" reading on this developer. I am...

www.photrio.com

that is very clear. Strangely it came out of a google search, but is not found by photrio's advanced search, despite giving all the relevant keywords.

Now to develop my first roll of Aviphot200...