Announcement: New SLIMT Technique 12-06-15

[davidkachel]

Some years back I swore off development of new techniques and also moved completely over to digital. This past month I bought a couple of view cameras, built a small darkroom and will be using film again, some of the time. (No, I haven't come back from the dark side. Will be using both.)
In about 2007, I tried to pass the baton here on APUG and on some other sites, like: http://photo.net/film-and-processing-forum/00REQ8
I also gave some suggestions for avenues of additional investigation. The most ripe and simplest of those suggestions was made at the address above. (Maybe here too. I don't recall.)
A couple of days ago I was reminded of that suggestion and, realizing I now had a working darkroom again, today I pursued that suggestion myself, and in just a couple of hours, had the answer.
There is a new SLIMT technique, as of today. It is called "Monobath SLIMT".
For those who do not know what a monobath is/was (originally), it is developer and fixer in the same solution. Monobaths were invented near the turn of the century. (Not this last one, the one before it.) Put simply, the developer is stronger than usual and acts on the film before the fixer can begin to work. Carefully formulated, this produces a well-developed negative and very consistent results. They were popular once, but fell out of favor.
Monobath SLIMT follows the same basic concept of mixing opposing actors, but instead of fixer, adds potassium ferricyanide to a normal film developer. At about ten or more times the concentration of a normal SLIMT, the potassium ferricyanide contrastwise bleach manages to reduce contrast of the latent image before the developer can begin to work. Theorized years ago, I never tested this until today. It works. Well!
Here is the test I did, your investigation will no doubt require different concentrations.
Film: HP-5 (4x5). Developer: HC-110 at half the concentration of dilution B (15.5 ml of syrup per liter of water, instead of 31 ml per liter), for 8 minutes, constant rotary agitation. Processing method: tube tray processing (my own variation, it can be found here: www.davidkachel.com/monographs.html "Tray Processing in Tubes"). 20ºC. Exposed a single negative. Cut it in half. Split the HC-110 into two trays, 1.5 L per tray, one tray with 50ml of 10% potassium ferricyanide added. Results: roughly N-2 contraction, perfectly even development, as you would expect from rotary processing.
Drawbacks: a much higher concentration than normal of potassium ferricyanide is required, and you cannot process different N-number negatives together in the same tray, for the same length of time, as you can with regular SLIMTs.
Advantages: one shot, one step development for any and all contractions, just change the amount of potassium ferricyanide.

This is the first new SLIMT in 25 years, guys. Don't expect another one any time soon! ;-)

ADDENDUM: SLIMTs for film usually require the addition of potassium bromide as a restrainer. That is not necessary in this case as most film developers already have a restrainer in them. Use just the potassium ferricyanide, unless the need for additional restrainer becomes obvious.

 

[MattKing]

David:

I've always been intrigued by SLIMT, and thank you for this.

One clarification please. When you say "HC-110 at half the dilution of dilution B" do you mean half the dilution/twice the concentration (1 +15) or twice the dilution/half the concentration (1 + 63)?

 

[davidkachel]

I could have worded that better, huh!
15.5 ml of concentrate per liter of water, I used it for years. Loved it. So, I just picked up where I left off. Have to extend development time of course.
Wording of original post now altered.

 

[Andrew O'Neill]

I used your SLIMT method as well as a your bleach and redevelopment in a monobath, for extreme contractions for years.

 

[davidkachel]

Thanks, Andrew. Good to hear. The "monobath method" (newcomers, this is something else, not the new "Monobath SLIMT") requires a lot of hair on your chest. Not for the faint-hearted. It even scared me!
Phil Davis called me right after it was published, said he didn't think it could work. I suggested he run his tests again. Found out later that really pissed him off. Not the last time I annoyed Phil, either.

 

[Athiril]

Tried this a few times on C-41 several years ago for reduced contrast.

Do you have results to show?

Can you demonstrate it actually works on the latent image, rather than weakening the developing power of the developer itself? Since it is an oxidising agent, and the developing agent, a reducing agent.

 

[davidkachel]

Athiril,
See Mees & James, "Theory Of The Photographic Process", 1966 edition, page 123. Or, consult any of thousands of people using SLIMTs since I first announced them in 1990.
Also, SLIMTs work exceedingly well on color negative film AND color printing papers. So well in fact that, in combination with a contrast increasing technique for color paper announced by Robert Anderson in the previous issue of D&CCT magazine to the issue where SLIMTs were announced, the world's first and only (and extremely effective and versatile) variable contrast control system for color printing was born. And as soon as that infant began to rise to its feet, a digital cross-town bus went speeding by and obliterated it from history! ;-)

(If you are still using C-41, you should try again, following the procedure exactly as outlined. SLIMTs are a quarter century old. They absolutely work.)

 

[Athiril]

David,

I think you're missing the point, you are mixing an oxidising agent together a reducing agent.

Potassium Ferricyanide and Hydroquinone are common chemicals to use to demonstrate oxidation-reduction reactions at schools, they observe the colour change of solution when mixing them together.

The potassium ferricyanide will oxidise some of the reducing agents, much faster than you can get the solution into your developing tank.

If you weaken a developer, and develop for the same time, temperature and method, of course you will have decreased development and hence reduced contrast.

 

[davidkachel]

Inreresting idea...

All of the original SLIMTs required extremely high dilutions, almost homeopathic, were applied prior to development and worked very well. At such dilutions they could not possibly have significantly effected the concentration of developing agents, especially in light of the fact that bleaching took place before the material reached a development bath.

The Monobath SLIMT does use a much less diluted bleach and is the only SLIMT where bleach is added directly to the developer. I suppose in theory that what you are saying might be possible, but the results say otherwise and were even achieved at the dilution I predicted would be required. A weakened developer could only become weakened by exhausting the bleach. (The amount used here is still a comparatively minute amount of bleach, compared to the amount of developer.) There is no evidence the bleach is used up. A weakened developer acting alone would produce results typical of past diluted development: substantial loss of film speed being the applicable result here. My test negative shows little to no loss of film speed (again, depending on how one measures film speed), one of the hallmarks of contrast reduction using a SLIMT.

Still, your criticism bears consideration. It is possible a combination of different reactions may be occurring. Since you brought it up, I think you should be tasked with devising a test to determine the truth in this case, don't you?! Let us know what you come up with. ;-)