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swmcl
16-May-2016, 16:58
If I may start a new thread just for the purposes ...

This question may just be answered by Doremus but others may also know.

The David Kachel articles describe how to make a potassium ferricyanide solution for use in the SLIMT process.

As I read it, 100g of potassium ferricyanide powder is mixed with 1 litre of water to make a stock solution. This stock solution is then watered down further to make a concentrated working solution. Can I ask what percentage you would call the stock solution in this example? Is this what you'd call a 10% solution ?

The 'concentrated working solution' is made by mixing 100ml of stock to 900ml of water. This would be what percentage ? Is this another 10% solution making it overall a 1% solution at this stage.

The instructions for using the bleach call for a further dilution to a 'final working solution'. This is suggested to be 20ml per litre of water of the above concentrated working solution. Would you then call this final working solution a 20/1000 * 1 = 0.02% solution ? Or do you call it a 0.002% solution ?

The use of percentages can be a little difficult to decipher at times ...

Cheers,

swmcl
16-May-2016, 17:28
Actually, I'll add my summary pdf.

Please let me know of any errors.

Thanks.

jrileystewart
26-May-2016, 09:51
I'm not an expert using SLIMT, but I've read up and thinking about some testing.
Instead of getting hung up on % concentrations, I mentally tagged them with more functional names.
1. Stock = 100gr / Liter K+FeCN-
2. Daily Working= 100mls/L Stock (this is only good for one day's processing
3. Batch Working= 20-50mls (IAW testing)/ L of Daily Working - (this is only good for one development batch)

I guess one could forego making up the Stock solution (which never goes bad) and just make up daily batches. In this case, you'd use 10 gr K+FeCN- into a Liter of water (that's 1.0 gram/100mls=1%)

Remember he also prescribed using the K+Br- solution (33 gr/L) as anti-fogging "for all B&W films" and "for all color films") so you'd need to make up (at least I would) another daily batch of 0.33% KBr. Might as well make up the Stocks and draw from that, I think. Easier in the long run than getting out the scales.

If I may start a new thread just for the purposes ...

This question may just be answered by Doremus but others may also know.

The David Kachel articles describe how to make a potassium ferricyanide solution for use in the SLIMT process.

As I read it, 100g of potassium ferricyanide powder is mixed with 1 litre of water to make a stock solution. This stock solution is then watered down further to make a concentrated working solution. Can I ask what percentage you would call the stock solution in this example? Is this what you'd call a 10% solution ?

The 'concentrated working solution' is made by mixing 100ml of stock to 900ml of water. This would be what percentage ? Is this another 10% solution making it overall a 1% solution at this stage.

The instructions for using the bleach call for a further dilution to a 'final working solution'. This is suggested to be 20ml per litre of water of the above concentrated working solution. Would you then call this final working solution a 20/1000 * 1 = 0.02% solution ? Or do you call it a 0.002% solution ?

The use of percentages can be a little difficult to decipher at times ...

Cheers,

Doremus Scudder
27-May-2016, 02:47
swmcl,

I saw this thread a little late, but I'll chime in anyway. I use SLIMT fairly regularly for Zone-System contractions up to N-4 or 5 (I rarely need more than N-2 or 3, but I've used more contraction occasionally).

I've adopted David Kachel's method for making up and storing the chemistry. First I make a 10% solution of potassium ferricyanide (A) and a 3.4% solution of potassium bromide (B). And yes, you are correct in thinking that 100g ferricyanide per liter is a 10% (weight/vol.) solution. For the bromide it is 34g of bromide/liter. A liter each of these will last you a long time. Be careful not to cross contaminate these. Clean your syringe or pipette thoroughly before and after sampling each chemical.

A note on mixing: start with slightly less than the total volume of water and top up the solution after you have added and dissolved the dry chemicals (more accurate this way).

For SLIMT contractions, my working solutions range from 0.04% to 0.005% (yes, all those zeros are correct, the dilution is very weak). I mix using a very small syringe marked in ml. I got several from my local pharmacy years ago. Here are my dilutions:

First, with the stock solutions as they are, one always uses the same amount of both. I use 500ml of solution in a deep 5x7 tray to treat the negatives before development, so my dilutions are for that total amount. If you need more volume, just do the arithmetic:

0.04% Dilution: 2ml A+2ml B per 500 ml

0.02% Dilution: 1ml A+1ml B per 500 ml

0.01% Dilution: 0.5ml A+ 0.5ml B per 500 ml

0.005% Dilution: I'll make up the 0.001% dilution above and then make it up to 1 liter, I just discard what I don't use.

As for figuring the final dilution: first, we're only talking about the dilution of the ferricyanide here, the bromide is just along for the ride :).

Example 1ml of a 10% solution contains 0.1g of ferricyanide (10g / 100ml = 0.1g/ml). Dilute that 0.1g to 100ml and you'll have a 0.1% solution; dilute it to 1000ml and you'll have a 0.01% solution (we're multiplying by 10s now). So here's a starting point: 1ml of stock (A+B) to a liter makes a 0.01% solution. 2ml/l = 0.02%, 4ml = 0.045 etc.

Figuring out your SLIMT times can be tricky. I'd shoot several test negatives and develop one normally, one normally with SLIMT pre-treatment 0.01% for 4 minutes and one with a SLIMT pre-treatment of 0.02% for 4 minutes. You can do the pre-treatments at the same time in different trays and have the N neg sitting in a tray of water. 15 seconds before the end of the SLIMT time, drain your negatives (all three) and transfer them to the developer all at the same time and develop for your normal time. Do whatever you do (proper proofs or densitometer readings) to determine what the results are and then adjust from there. Once you have a benchmark for one film/developer combination, you can extrapolate more or less contraction and test that. Keep in mind that SLIMT times vary widely from film to film, so your tests for one film are not valid for another. I had to revise my SLIMT times for TXP when Kodak reformulated it and started coating it at the new coating facility...

Hope this helps,

Doremus

Steve Sherman
27-May-2016, 16:53
Thanks very much for posting this Doremus !!

Greg
27-May-2016, 18:16
Reminds me of the technique W. Eugene Smith used of selectively painting on a solution of potassium ferricyanide to "bleach" out white areas in his prints. His dilutions were "made by eye". When the bleaching process was 90% there, you'd immediately put the print into the fix to stop the bleaching action. Used this technique a lot in the late 1970s and 1980s. You had to go "too far" dozens and dozens of times to learn how to get it right... very much akin to Lith printing (pulling the print from the developer into the stop just before getting the results you were after) back then. Just my 2 cents.

Doremus Scudder
28-May-2016, 03:49
Reminds me of the technique W. Eugene Smith used of selectively painting on a solution of potassium ferricyanide to "bleach" out white areas in his prints. His dilutions were "made by eye". When the bleaching process was 90% there, you'd immediately put the print into the fix to stop the bleaching action. Used this technique a lot in the late 1970s and 1980s. You had to go "too far" dozens and dozens of times to learn how to get it right... very much akin to Lith printing (pulling the print from the developer into the stop just before getting the results you were after) back then. Just my 2 cents.

Greg,

What you're referring to is different than SLIMT. Local and overall bleaching of prints to increase contrast, bring up the whites, etc. is a time-honored and well-established practice. Many of us make up solutions for this "by eye," and experience, kind of knowing what color of pale yellow will work well and adjusting as we go.

SLIMT is different in that the material is treated before development and it is the latent (undeveloped, but exposed) image that is affected by the bleach. This is a contrast-reduction technique that works for both negatives and papers.

Thanks very much for posting this Doremus !!

My pleasure Steve. If you and others are interested, you can get the info from the "horse's mouth" here: http://www.davidkachel.com/assets/cont_pt3.htm . All of David Kachel's monographs are worth reading. Unfortunately, they don't seem to be available from his home page due to dead links on his site. However, you can find the titles there and then just Google-search on his name and the title and find the pages with the articles.

Best,

Doremus

swmcl
1-Jun-2016, 00:09
Doremus,

Thank you for the clarifying post.

Q 1. Is the film latency or whatever you might call it an issue here ?

Should we mix weaker solutions and run them for a longer time so as to overcome and take-up issues ? Assuming rotary washing machine type processor.

Q 2. Is PhotoFlo out of the question for this part of the development process ? Some film has a surfactant built-in of course ...

Rgds,

Steve

Doremus Scudder
1-Jun-2016, 02:48
Steve,

I haven't run into any problems with the permanence of the latent image in conjunction with using SLIMT, if that's what you're referring to. I sometimes wait up to a couple months to develop when on the road and have never seen any ill effect. That said, I don't use FP4, which is said to have less-stable latent-image keeping properties.

If you're talking about induction time, i.e., the time it takes for the solutions to soak into the emulsion and start working, then I would think that whatever issue you might have here, if any, would be compensated for in the testing process. Just be consistent. I tray process, but if I were using SLIMT and rotary processing, I would certainly include a water pre-soak in the work flow. As an aside, part of the beauty of using SLIMT for contractions is that you can use your "N" development times, meaning that you can develop contraction negatives together with normal ones.

As for using PhotoFlo: I have never used, or seen the need to use a wetting agent at the development stage. I use it only as a final rinse before hanging the film to dry. If you are somehow trying to speed up induction time by using a surfactant, then I don't think you'll gain much. With rotary processing I think there would be a distinct risk of foaming and resultant development defects. I can't really think of a scenario where a wetting agent before or during the development stage would be necessary. I'd recommend against it. I'm not sure there are films with surfactants built into the emulsion either...

Furthermore, if pouring-in time for the developer is rather long, i.e., it takes a while to get the film completely evenly covered, as is often the case with rotary processing and large tanks, I would think that a surfactant would just make things worse. Perhaps this is what you meant when you referred to take-up times and higher dilutions. In this case, a higher dilution coupled with a water pre-soak and longer working times will certainly make the difference in contact times a much smaller fraction of the entire treatment process and would be an avenue to explore if there are signs of unevenness.

Hope this helps,

Doremus

swmcl
1-Jun-2016, 13:32
Doremus,

The query about induction times is simply a query as to whether the bleaching solution follows the developer in its behaviour. At my developer concentration, the activity drops below the 5min mark. This means if one were to pull the film at or before the 5min mark one could expect irregular and uneven development. I am querying whether the same 'curve' applies to the bleach. If there is a latency, then there is a minimum time for bleaching also.

The use of a little PhotoFlo in the pre-soak is to ensure even wetting of the film. I use a couple of drops and there is no foaming. Absolutely no ill effects at all. My concern at this stage is whether a PhotoFlo would react with the bleach.

It may not be a going concern really because I would be using a large amount of dilute bleach. There is no way the film wont get evenly wet considering it will be inside a tub with a relatively huge amount of fluid and there is no need to go slow so it will be seriously sloshed around.

Yesterday I mixed up 4 litres of each the bleach and the anti-fogging. Going by your concentrations that might be around 4000 litres of bleaching solution !! I think I have enough.

Steve

Doremus Scudder
2-Jun-2016, 01:11
Steve,

I don't know where you got the term "latency" in respect to how long it takes developer (or any chemistry, for that matter) to soak in and start working. I've never heard of it in that sense (perhaps there's a hole in my education here). There is an induction time but that is separate from any unevenness that might occur with shorter development times, which is largely due to uneven immersion and turbulence in the initial agitation, which cause areas of increased/decreased developer activity that tend to even themselves out over time. At any rate, that happens with all chemistry that we use on film to a greater or lesser degree depending on the aggressiveness of the reaction. So, if you're asking is there a minimum time for the bleach step to avoid unevenness, then yes, there is theoretically. I have, however, seen no unevenness using SLIMT and bleaching times of 3-4 minutes. You should be good with times in that neighborhood.

If using a wetting agent pre-development is working for you, then fine. I've never done this and don't know if it helps anything or not.

Four liters each of 10% ferricyanide and 3.4% potassium bromide! That's enough to last me a lifetime. The good thing here is that the solutions will last practically forever if you don't contaminate them and you can use them for print bleaching and for bleach/redevelop of negatives. I use the same stock solutions to mix these other bleaches too.

Have fun,

Doremus

swmcl
9-Jun-2016, 23:18
Back again, ...

I have attached a pdf of my results.

The light blue graph is the control. An 'N' development in 6min 30sec.

I initially did a 0.01% ferricyanide bleach (with the bromide solution of course) for 5min and got the red graph. I calculate this to be around N+0.66

Then I did a series of other runs with increasing times which didn't seem to affect the low tones as much as they did the higher more dense tones. There is also a dud in there - the yellow graph.

Lastly, I did another run at 5min but with double the concentration of ferricyanide at 0.02%. This one gives me an N+2.33 or so. The dark blue graph.

The conclusions I come to are that one should not try to bleach for a longer time with the same concentrations as the results are haphazard. One should bleach for a consistent time but vary the concentration of the bleach.

So for the N+0.66 I put 0.4ml of the 10% solution in 400ml of water and agitated for 5min.
For the N+2.33 result I put 0.8ml of the 10% solution in 400ml for 5min.

The results are positive and quite smooth when the bleaching time does not go for too long.

I'm using a Jobo 3006 tank that I hand roll at 10sec per revolution at 20 degrees C.

HP5 sampled at ISO100. Pyrocat-HD 5:5:300

I could possibly be better off standardising at 4min given the wrinkles in the dark blue graph.

Doremus Scudder
10-Jun-2016, 00:39
You do mean "N-" instead of "N+" in the above, don't you?

swmcl
10-Jun-2016, 02:19
Ooops.

Yes.

I'm thinking of the extra stops on paper. So please read N-0.66 which means another 2/3rds of a stop on paper.

The other would be 2 and 1/3 extra stops on paper.

Ahhh terminology and precision !!

Also, ... I estimate the ISO to drop another stop when using SLIMT.

Trust it all makes perfect sense !