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albada
02-05-2012, 06:07 PM
What does sulfite do? How much is needed for a fine grain effect? Is more better?

I noticed that when mixing developers, I'd add a little of this and a little of that, and drown it all in a large mound of sulfite. So I said "this is ridiculous", and started trying to reduce sulfite. My basic method was posted earlier as "half and double": Cut sulfite in half, and double the dev-time. But I still wondered what different amounts of sulfite actually did, so I formulated the following four developers:


Sodium sulfite ................. 22, 33, 45, 90 g
Sodium metaborate ........ 2.7, 2.4, 2.0, 1.0 g
Ascorbic acid .................. 4.5 g
Phenidone ...................... 0.05 g
Target pH=8.0. Starting times are twice XTOL's times. For TMY-2: 13 min @ 20C.


I kept the pH and dev-time the same for all of these. The results below are labeled with the amount of sulfite:

22: Too thin, and I asked about this earlier in this thread. Based on PE's reply, it appears that Tmax-400 (TMY-2) works poorly with this brew.
33: Looks good. Grain is at least as good as XTOL or a hair finer, with a hair better shadow-detail.
45: Looks good. Grain is at least as good as XTOL or a hair finer, with a hair better shadow-detail.
90: Too dense with coarser grain. Shadow-detail matches XTOL.
90 retried at 11.5 min instead of 13 min: Slightly thin, grain is a little rougher than XTOL, and there's a hair less shadow-detail.

It's hard to tell the difference between 33 and 45. I slightly prefer 45 because the grain is slightly less wormy-looking in some cases. In practice, most people could not tell the difference between these two.

My conclusions:

Even keeping pH constant, the proportion of sulfite affects density.
A long soak in high sulfite can make grain worse instead of better.
You can get top quality with much less than 80-100 g/L of sulfite.

That last point is good news for my concentrate-project: It means one can get great quality without using much chemistry.

Mark Overton

Photo Engineer
02-05-2012, 06:19 PM
Mark;

Great experiments. Before you know it, someone else will be selling this stuff!

You are looking at the solvent activity of Sulfite at higher concentrations and also the buffer capability (to a lesser extent).

There you are.

Sulfite is also your preservative to a certain extent, extending the life of the developer.

PE

Michael R 1974
02-05-2012, 06:47 PM
Why would a long time in a sulfite-rich solution, in and of itself increase graininess? That seems odd, unless what you're seeing is simply more development taking place due to the developing agents being better preserved by the higher sulfite level, which would indeed increase graininess. But that's not "direct" action by the sulfite. Consider D25 versus D23. The only difference is the lower pH of D25, resulting in longer contact with the sulfite for finer grain than D23.

Then again I'm no chemist so take my comments for what they're worth :)

albada
02-05-2012, 06:56 PM
Great experiments.

Ron, thanks for the note. And that makes two of us who are not watching the superbowl. :)

BTW, thanks for the responses yesterday about sharpness.
In my report of four developers two postings ago, I didn't mention sharpness because it's hard to see any difference among these developers and XTOL.

Yesterday, Rudeofus mentioned that SMAP is restrictive. True, but for a concentrate, I'm not restricting myself to metaborate-ascorbic-phenidone. For example, Boric acid is a worthy chemical for a concentrate, and buffers well with metaborate. TEA is another. But I'm finding that one can accomplish surprising things with only the four SMAP components, so I'm using them as my baseline for experiments.

EDIT:
Michael R 1974 responded while I was typing the above, so I'll respond here. He wrote: "Why would a long time in a sulfite-rich solution, in and of itself increase graininess?"
That's what I saw in 22X loupes for the 90-case. But on re-exam, the graininess per se is about the same, but the appearance of the grain is more "wormy" for lack of a better word. XTOL and the others have more uniform grain, but 90's grains are more often connected to each other, forming black worm-like lines. The white areas between grains can also connect, forming white worms. Obviously, I don't know what causes or prevents these worms.

Mark Overton

Photo Engineer
02-05-2012, 07:23 PM
Ok, Sulfite is a silver halide solvent. Long contact with concentrated Sulfite allows many many things to happen. The simplest way to explain this is that the tiny slow grains or the low iodide slow grains will dissolve courtesy of high Sulfite. The longer you are in contact with this developer the more chance you have of depositing this silver on other developing grains in the mid tones or elsewhere. As a result, the silver metal "grains" become abnormally large due to the extra silver being deposited.

This leads to coarser grain.

There are others reasons such as the fact that solvent developers can change edge effects and change visual contrast thereby subtly altering the visual appearance of grain making it appear worse.

Many many things going on here.

PE

Ryuji
02-05-2012, 07:38 PM
[...] he has enough sulfite to renew used ascorbate. If Mark wants sharpness aka edge effects, he needs to design a developer which breaks down locally from heavy use. He can do that either by using a higher dilution, by weakening his buffering (less ascobate and metaborate for same pH), reducing agitation or by making sure that oxidised ascobate won't get replaced&restored (less ascorbate&sulfite).


Oxidized ascorbates are not regenerated by sulfite. The oxidation reaction is quite complex depending on the condition, but the reaction pathways that matter in this context, the mechanism is very different from that of hydroquinone.



To be honest: designing a developer, using only four easy to obtain components, which smacks Xtol in grain, sharpness and speed in more than very few special cases sounds like a very ambitious task.


That’s right. When I look back my work in DS-10, which was intended to err slightly on the safer side with the knowledge I had at that time, knowing that pH of 8.0 was a slightly risky choice, I can simplify it a bit now, but I can only remove three ingredients (but must add one new agent) without sacrificing the stability/reliability of the developer.

Ryuji
02-05-2012, 07:48 PM
Why would a long time in a sulfite-rich solution, in and of itself increase graininess? That seems odd, unless what you're seeing is simply more development taking place due to the developing agents being better preserved by the higher sulfite level, which would indeed increase graininess. But that's not "direct" action by the sulfite.

This is a very good and relevant question.

Some people here seem to jump to fallacious conclusions... many equate sulfite with solvent, solvent with physical development, physical development with fine grain effects, where each association here is problematic. For example, sulfite does a number of other things than dissolving silver halides. Solvent effect does not entail in physical development. Physical development may make larger or finer grain, often within the same emulsion and same developer. So, making a grand fallacy of sulfite = fine grain is misleading, but some seem to be trapped with it.

If the reported experiment was done very carefully, the most plausible explanation of the result is that sulfite acted as a mild “disinhibitor” or accelerator of development process, and this is well known.

Rudeofus
02-06-2012, 02:33 AM
Sulfite is also your preservative to a certain extent, extending the life of the developer.
That's a nice property of sulfite but I assume Mark mixes his soups as he uses them, so preservation seems less of an issue here.


Oxidized ascorbates are not regenerated by sulfite. The oxidation reaction is quite complex depending on the condition, but the reaction pathways that matter in this context, the mechanism is very different from that of hydroquinone
Oops. Read too many articles on superadditivity and got that mixed up apparently. So much for "learn photo chemistry in 24 hours" :unsure:


Yesterday, Rudeofus mentioned that SMAP is restrictive. True, but for a concentrate, I'm not restricting myself to metaborate-ascorbic-phenidone. For example, Boric acid is a worthy chemical for a concentrate, and buffers well with metaborate. TEA is another. But I'm finding that one can accomplish surprising things with only the four SMAP components, so I'm using them as my baseline for experiments.
The biggest advantage of restricted choice of ingredients is that the number of experiments doesn't go through the roof, so there's a good chance we as amateurs can even reach the optimum of what is possible with these ingredients. But lets not forget that Kodak could afford lots of engineers, lots of experiments and had lots of exotic compounds at hand so there is a good chance that Xtol will always be superior to SMAP except for a few special cases. The original question you asked about your SMAP sounded like "I beat Xtol in grain size and speed, how come it's still better in sharpness?".

Instead of beating Xtol in all respects we could focus on beating it in a few relevant parameters so we can mix and match dev depending on application. I would love to create a set of 10 recipes, all using the same set of easy to get ingredients only in different concentrations and which would cover the whole speed/grain/acutance triangle. Current recipe collections (http://www.digitaltruth.com/data.php?doc=filmdevs) read like books about cocktail mixing, where you need 10 different ingredients for 3 cocktails and 20 if you want to mix 6 of them.


There are others reasons such as the fact that solvent developers can change edge effects and change visual contrast thereby subtly altering the visual appearance of grain making it appear worse.
Yes to that. Let's not forget that the grain we observe is not the individual silver grains but a superposition of them. A lot of things have an effect on visual grain, actual silver grain size is only one of them.

Keith Tapscott.
02-06-2012, 03:14 AM
Oxidized ascorbates are not regenerated by sulfite. The oxidation reaction is quite complex depending on the condition, but the reaction pathways that matter in this context, the mechanism is very different from that of hydroquinone.



That’s right. When I look back my work in DS-10, which was intended to err slightly on the safer side with the knowledge I had at that time, knowing that pH of 8.0 was a slightly risky choice, I can simplify it a bit now, but I can only remove three ingredients (but must add one new agent) without sacrificing the stability/reliability of the developer.Would you reveal your formula for those interested in trying it?

Ryuji
02-06-2012, 09:53 PM
Would you reveal your formula for those interested in trying it?

I might be cynical here, but I'm not into publishing every little variants of so many developers I made and tried and used just because they are different. They made the same photographic effects for all practical purposes.

You might want to go to a Hong Kong restaurant, and ask your server, what's the difference between yesterday's and today's daily soup?

Then do you see the title of this thread? "Improved version of DS-10 by Ryuji Suzuki?" You don't want to see me if the title did not end with a question mark.

But one thing I can reveal now is that, the reason why I used that much TEA (and would've used more if I felt like it) and salicylic and boric acids was to increase the stability of the developer. I am ok with less of these ingredients, and zero salicylic and boric acids, only because I have a much more powerful developer stabilizer (which was used for Tektol developers after the packaging changed).

Ryuji
02-06-2012, 09:58 PM
Instead of beating Xtol in all respects we could focus on beating it in a few relevant parameters so we can mix and match dev depending on application. I would love to create a set of 10 recipes, all using the same set of easy to get ingredients only in different concentrations and which would cover the whole speed/grain/acutance triangle.

That's what I've been saying for years... since when I was using precursors to DS-1 and DS-2.

Gerald C Koch
02-06-2012, 11:14 PM
May I recommend the following article as it explains many of the design factors concerning the formulation of Xtol. This article may be hard to find but is worth reading. It is no longer on the PT website but copies of it do exist on the web.

The Genesis of Xtol
Dick Dickerson and Silvia Zawadski
Photo Techniques Vol 20, #5

albada
02-07-2012, 09:58 AM
I might be cynical here, but I'm not into publishing every little variants of so many developers I made and tried and used just because they are different.

On the other hand, publishing a formula allows for community-review and community-testing, which helps catch flaws. In the software-community, this is called "open-sourcing", and it's popular -- for good reason.


the reason why I used that much TEA (and would've used more if I felt like it) and salicylic and boric acids was to increase the stability of the developer

I've never heard that boric acid is a stabilizer. Is that merely because it's an acid, or is there something else about it that helps stabilize?

Mark Overton

Ryuji
02-08-2012, 02:38 AM
On the other hand, publishing a formula allows for community-review and community-testing, which helps catch flaws. In the software-community, this is called "open-sourcing", and it's popular -- for good reason.


On the internet you can find a lot of competent software engineers. That is not the case on this forum.



I've never heard that boric acid is a stabilizer. Is that merely because it's an acid, or is there something else about it that helps stabilize?

I didn't say boric acid is a stabilizer. Triethanolamine and salicylic acid are. In many practical chemical choices one has to make, one just can't change one thing without balancing other factors.

Rudeofus
02-08-2012, 05:15 AM
On the internet you can find a lot of competent software engineers. That is not the case on this forum.
Don't underestimate the number of competent software engineers in this forum :p


@Mark: The original formulas for DS-10 (http://www.digitaltruth.com/data/ds-10.php) and DS-12 (http://www.digitaltruth.com/data/ds-12.php) were published a long time ago, and as far as I have understood the main issues Ryuji has dealt with since then were longevity and manufacturability while keeping the dev properties the same. For all open sourcerers amongst the home brew crowd we have the raw source ingredients, but we won't get the nice packaging for free. Remember, Ryuji made several attempts at commercializing his devs in the past. Rather than screaming that everything should be free for us we should be grateful that he helps us here in the forum.

Ryuji
02-08-2012, 11:57 AM
For record, DS-10 and DS-12 were not designed with manufacturability in mind. I was still focusing on making the developer stable for practical routine processing.

I did not publish any formula that was specifically made with manufacturability in the scope. The first generation Tektol developers were a one-step forward from DS-14, but the second generation Tektols were further improved. But then Tektol is no more. One reason why I don't publish the formula for Tektols in part has to do with the ingredient (developer stabilizer) not available from anywhere but Silvergrain, but chemical sales is not my business... When Silvergrain chemicals were offered for sale, I actually prepared the stabilizer additive and shipped it with instruction to the factory under nondisclosure agreement. The entire formula was under the scope of NDA but there was no better way to do this. Suppose the darkroom chemical market is 7000x larger than what it is today, and if it makes sense to do Silvergrain chemical again, I'd actually set up my own mini-plant. While I accumulated a lot of insight and know-how as to how to prepare ascorbate developers with minimum of aerial oxidation during manufacturing, I think the factory people didn't like to be told what to do, so a lot of my knowledge wasn't utilized effectively. Believe or not, when factories prepare developer concentrates, the solution is heated, stirred and poured for hours from start to finish, and many of the mixing apparatuses are made from stainless steel, so there are a lot of things that would be ok with hydroquinone developers but not with ascorbate developers.

A lot of people don't realize, but if you pour hot water in a stainless steel vessel, a trace amount of iron goes into the water. This level of iron is significant for unprotected ascorbate solution. The second generation Tektol had a stabilizer that deals with this problem. I use the same technique for my film developer, so that I have no concern using stainless reels and tanks (which are made from lower grade stainless steel than chemical mixing vessels).

Tronds
02-08-2012, 12:39 PM
Don't underestimate the number of competent software engineers in this forum :p



Yes, there are several of them, and they know problem solving and testing.

Ryuji
02-08-2012, 03:11 PM
Yes, there are several of them, and they know problem solving and testing.

How many people here actually have experience in debugging misconceptions, gross oversimplifications, and other errors in popular darkroom "chemistry" books?
How many people here actually identified a problem, formed a design objective and offered practical solutions to it through a systematic approach?
How many people here have a paper on photographic chemistry published in a peer reviewed academic journal?

There used to be a couple, but they've moved on.

Tronds
02-08-2012, 05:36 PM
How many people here actually have experience in debugging misconceptions, gross oversimplifications, and other errors in popular darkroom "chemistry" books?
How many people here actually identified a problem, formed a design objective and offered practical solutions to it through a systematic approach?
How many people here have a paper on photographic chemistry published in a peer reviewed academic journal?

There used to be a couple, but they've moved on.

Soooo, because there are people here actually have experience in debugging misconceptions, gross oversimplifications, and other errors in popular darkroom "chemistry" books, other trained people don't understand anything, and just speaks nonsense?

There are infact several people that have read some more than popular darkroom "chemistry" books, but writing a comment here is not accepted.
Doing so starts the "newbie bashing".

Well, that's ok. There are several people that have stopped writing constructive postings here beacause of this.
Many have moved on because of the hostile anvironment here.
I for sure won't discuss my work in here. Neither will I try to help when someone asks for help with a problem.
The forum Gods have to step up and offer help, IF they want, and isn't in the bashing mode.

Photo Engineer
02-08-2012, 06:39 PM
Interestingly enough, between APUG and Photo Net there are about 4 Kodak photo engineers making comments. They are still here, and still plod away. Mix in with that the fact that my original Blix formula went on sale by Kodak in 1970 and is still on sale in slightly modified form today. The corresponding color developer went on sale in 1970 as well and sold until the RA 4 process came into use.

The Fomulary's Liquidol and TF-5 have been and remain on sale for our B&W friends, and more developers and fixers are in the pipeline just waiting for completion of tests.

I was one of the "peers" who reviewed Grant Haist's two volume set, and have had many publications and patents as have the others who contribute here.

I also led a group of software engineers in developing the Kodak Emulsion Design and Scaling System.

So, I would say you have a pretty fair chance of getting a usable answer from me or one of my friends. If not, I can always consult with them and get back with an answer. I have tried to do that for Mark and others.

The number of highly qualified people posting here is greater than one might expect and they are willing to share information unless it is proprietary and they are bound by an outside NDA. A self imposed NDA is at the discretion of the originator, of course.

PE