Improved version of DS-10 by Ryuji Suzuki?

[Photo Engineer]

It depends also on pH. A well buffered system does not go down in pH. There are so many factors that it is difficult to say.

PE

 

[Rudeofus]

Why does 1+1 dilution (with XTOL anyway) increase grain compared to 1+0?

Because you dilute not only the dev agent but also the solvent? You recently posted recipe doesn't do that. If you want to investigate the influence of one parameter on the outcome of your experiment, it's imperative that you really change only this one parameter or the comparison won't tell you much

With a concentrate, there's a trade-off between concentration and dev-time, and the longer time that's associated with higher concentration means a little more grain (and I'm wondering why). I'm recovering that loss of quality by dropping pH, boosting time even more. As PE said, "What's the hurry?"

As mentioned before, we/you won't be able to beat Xtol on all terms, but you/we have a reasonable chance to achieve better image quality if we relax some of the design rules which apply to commercial devs. Short dev time is one of them, sufficient capacity (250ml enough for 36 exp. 135 film) would be one, long shelf life could be a third. With your low pH experiments we might once create a dev which only works reliably if we measure and adjust the pH before every run.

 

[Ian Grant]

Why does 1+1 dilution (with XTOL anyway) increase grain compared to 1+0?

As Rudeolfus says the dilution cuts the Sulphite level which is the key to grain control in many developers like D23, D76/ID-11 etc as well as Xtol.

In practice the 1+3 dilution gives the worst grain and Kodak have dropped that dilution from their datasheets for both Xtol and D76 in recent years. However with dilution there's a trade off of increased grain compared to increased sharpness and acutance and a good balance point is a dilution of 1+2.

The critical level of Suphite appears to be around the 25-30 g/litre but this may vary with films but my own experience with both D76/ID-11 and Xtol and Fp4 and Tmax 100 is that grain control with both developers is good at 1+2 dilution but for optimum results in terms of fine grain, acutance and sharpness replenished Xtol is better still.

Ian

 

[albada]

Because you dilute not only the dev agent but also the solvent?

Hmmmm... And Ian Grant also suggests this.

Diluting 1+1 cuts sulfite in half, but dev-time doesn't double, and even if it did, solvent-effect isn't linear. So there's less solvent-effect, and that would make sense why 1+1 would worsen grain.
Thanks for pointing this out.

Different question:

How do folks feel about measuring a concentrate by weight instead of by volume? I love my electronic gram scale, but would most users of a developer want to buy one? Or would most folks prefer to measure by volume using a graduate? That's fine for concentrate, but it means greater error when measuring sulfite. Do you think most non-home-brewers would be put-off by measuring by weight?
BTW, potassium sulfite concentrate makes it easy to measure everything by volume. It's a pity that it's hard to obtain in much of the world.

Mark Overton

 

[Rudeofus]

How do folks feel about measuring a concentrate by weight instead of by volume? I love my electronic gram scale, but would most users of a developer want to buy one? Or would most folks prefer to measure by volume using a graduate? That's fine for concentrate, but it means greater error when measuring sulfite. Do you think most non-home-brewers would be put-off by measuring by weight?
BTW, potassium sulfite concentrate makes it easy to measure everything by volume. It's a pity that it's hard to obtain in much of the world.

Under all normal circumstances measuring by weight is the thing to do, after all we usually don't deal with solid blocks of material but with powders and flakes, where density may vary, and moles are directly tied to weight, not volume. The only big exception are solutions, because dilution is commonly measured by moles/liter or kg/liter. In this case the volume of the liquid, aqueous or not, is directly proportional to the moles of agent and therefore the most easy to use measure of total agent amount. If you go through the effort to measure the density of such a solution, you can easily convert between volume and weight of such a solution.

It is clear that a 2% solution of X contains twice as many grams or moles of X per volume than a 1% solution. In terms of weight, there is no such easy relationship, since volume of a liquid may rise or shrink if you dissolve a substance. There is no simple rule to determine the density of a solution!

Personally, I wouldn't worry much about the requirement to get a scale which measures 0.01g. You are right on track towards very critical developers where tiny deviations in some components could trigger big differences in results. You have noticed yourself that you do no longer write about pH of 9 or 10 but about 7.95 and 7.92. My recommendation to everyone trying your latest recipes would be: plunk down money for a moderately precise scale, it's not going to break the bank and ensures that you get results similar to Mark. If you want to experiment on your own, go get a decent pH meter, too, or your results may vary to much to be repeatable and useful to others.

 

[Ian Grant]

Hmmmm... And Ian Grant also suggests this.

Diluting 1+1 cuts sulfite in half, but dev-time doesn't double, and even if it did, solvent-effect isn't linear. So there's less solvent-effect, and that would make sense why 1+1 would worsen grain.
Thanks for pointing this out.

When I used D76 and later Xtol dilute my own experiences were that any slight increase in grain at 1+1 & 1+2 was out weighed by the overall increase in sharpness and acutance. It's that balance of grain, sharpness and acutance along with tonality are important, and we don't all want the same balance.

When looking at the sulphite concentration it has to be remembered that dropping the level in a developer like D76/ID-11 fro 100g/litre to 80g/litre results in an increase in developer activity but no increase in grain, Agfa 44 (Agfa Ansco/Gaf 17) and Adox Borax MQ both give less speed loss, better sharpness and slightly finer grain, which leads to smotther tones.

The ratio of Hydroquinone to Metol also plays a part, in D76 it's 2.5:1, Adox Borax MQ and Agfa 17 it's 2:1 while in the oldest Fine grain developer I've come across it's 1:1. Welington & Ward's Borax MQ developer (for delicate Fine Grain negatives) pre-dates the first Fine Grain developer published by Kodak by a few years - Kodak eveolved this formula into DK50.

Ian

 

[albada]

Yet another question for the chemists:
Among PG-soluable acids and bases, which acid-base pair gives the most buffering per gram of total weight?

In my present version of the concentrate, I have 7 grams/liter to allot to an acid and base to (1) set the pH to 8.00, and (2) provide as much buffering as possible. I can do things like:
6.5 grams of sodium metaborate plus 0.5 grams of citric acid, or
3.5 grams of sodium metaborate plus 3.5 grams of boric acid, or
6.5 grams of TEA plus 0.5 grams of citric acid, or other possibilities.
BTW, the numbers above are rough guesses. And they assume that ascorbic acid and sulfite are/will be added.

It's easy to adjust pH, but I'm wondering what combo maximizes the buffering, especially between the first two possibilities above.
Thanks!

Ian: Thanks for the reminder about trade-offs between fine grain and acutance. Also, I want to explore Metol, Hydroquinone and PPD, but there's only so much time...

Mark Overton

 

[Photo Engineer]

The answer to your question varies with pH.

PE

 

[Rudeofus]

6.5 grams of sodium metaborate plus 0.5 grams of citric acid, or
3.5 grams of sodium metaborate plus 3.5 grams of boric acid, or
6.5 grams of TEA plus 0.5 grams of citric acid, or other possibilities.
BTW, the numbers above are rough guesses. And they assume that ascorbic acid and sulfite are/will be added.

At the start of this thread you posted a link to a pH calculator, maybe now's the time to put it to use. It's easy to calculate the moles from weight so you have the concentration. pKa and pKb can be found online, especially for the substances you listed here. Fine tune the mix to get the pH you need, then (virtually) add HCl or NaOH to your setup and see how much the calculated pH level changes.

It's easy to adjust pH, but I'm wondering what combo maximizes the buffering, especially between the first two possibilities above.

If it's easy to adjust the pH of a buffer, then it's a poor buffer

 

[Kirk Keyes]

I have a feeling he means it's easy to make a buffer for a particular pH...

 

[albada]

I have a feeling he means it's easy to make a buffer for a particular pH...

That's correct. It's easy to add base or alkali while watching the pH-meter until a target-pH is reached. But it's hard (for me) to determine which choice of chemicals yields the strongest buffer.

Ron: My target pH is 8.0. Sorry I forgot that detail. Forgetting details is something I'm good at; I call it one of my "core competencies".

It occurred to me during my half-hour walk today how to answer my own question: Mix up the chemicals, and measure pH-shift resulting from adding a little base or alkali. Select the brew that gives the smallest shift. Problem solved. This evening I measured the metaborate/boric-acid combo. Tomorrow will be the metaborate/citric-acid combo.

BTW, I discovered a quick way to dissolve boric acid: While mixing the chemicals, heat a little water in a separate beaker on the side. When it's up to 60-70C, add the boric acid. It dissolves within a minute. Then pour that beaker into the brew.

Mark Overton

 

[Rudeofus]

That's correct. It's easy to add base or alkali while watching the pH-meter until a target-pH is reached. But it's hard (for me) to determine which choice of chemicals yields the strongest buffer.

Sorry, but I was right. You can change a buffer to any pH value by adding copious amounts of KOH or HCl, but outside its ideal range it won't buffer well. There are many docments to be found online which show the borax/boric acid buffer combo to be exactly where you want it: almost symmetrically around a pH value of 8.

Ron: My target pH is 8.0. Sorry I forgot that detail. Forgetting details is something I'm good at; I call it one of my "core competencies".

The borax/boric acid buffer is frequently used in devs, so it is well understood and doesn't interfere. Since pH of 8 lies in the center of its range, I'd suggest you use it. Be careful with Borax, it dissolves poorly at 20°C. Sodium metaborate is easier to dissolve but its pH is too high.

It occurred to me during my half-hour walk today how to answer my own question: Mix up the chemicals, and measure pH-shift resulting from adding a little base or alkali. Select the brew that gives the smallest shift. Problem solved. This evening I measured the metaborate/boric-acid combo. Tomorrow will be the metaborate/citric-acid combo.

Look at borax/boric acid, borax is much cheaper than metaborate and you need less boric acid to reach the pH you want. Don't waste your time&money mixing endless rows of combos, use that online pH calculator you posted about. You may well find out that one buffer combo works slightly better than the other but that the difference is not worth the trouble at this stage. If buffering is really an issue, just use more soup with the same amount of film!

 

[Photo Engineer]

I would have to say that Boric Acid / Borax is one of the best choices with the rations balanced to get the target pH and the total quantity being above 20 g/l and not more than 3/4 saturation for a start. Another combination is Carbonate / Bicarbonate.

PE

 

[Rudeofus]

I would have to say that Boric Acid / Borax is one of the best choices with the rations balanced to get the target pH and the total quantity being above 20 g/l and not more than 3/4 saturation for a start. Another combination is Carbonate / Bicarbonate.

If you use borax/boric acid, plan ahead, borax just doesn't want to dissolve fast, even at 40°C And I mean many hours, not minutes ...

Carbonate/bicarbonate is described here, but it is claimed that only pH values between 9 and 11 can be reached. For pH of 8 and good buffering something more acidic must be used. How about Dead Link Removed? Both components are much more water soluble than borax.

 

[albada]

If you use borax/boric acid, plan ahead, borax just doesn't want to dissolve fast, even at 40°C And I mean many hours, not minutes ...

I've dissolved Borax at room temperature, and it only took a few minutes to dissolve. The Borax available here in the USA is sodium tetraborate decahydrate. Is that what you've got? Anyway, I dissolved it at up to 9 g/L; perhaps you are pushing it higher, closer to the solubility limit.

I've resisted using Borax because of the ten water molecules on it. I'm designing a concentrate, and I'm unhappy enough with having two water molecules on some sodium metaborate. With five times as much water in it, my instructions will have to say, "Keep the concentrate hot until the steam stops forming condensation on your safety glasses."

Although, maybe that extra water will steam-out quickly enough and won't be an issue. I might try it.

The concentrate formula I'm narrowing-in on looks like:

Propylene glycol (80-90C) ....... 25 ml
Sodium metaborate 4 mol ....... 3.5 g
Ascorbic acid ........................... 6 g
Boric acid ................................ 4.2 g
Phenidone ............................... 0.08 g
Propylene glycol to .................. 33 ml (1+29 dilution)

pH = 8.0. One liter of dev contains 66 g of sodium sulfite and 33 ml concentrate (1+29).
Time for TMY-2 at 20C is 10.5 minutes.

​

Today I'll test this formula using citric acid instead of boric. Any comments/critiques of this approach are welcome.

Mark Overton

 

[Photo Engineer]

Well, Phosphates are not very good buffers and the only evidence I can offer is the fact that EK does not use them in any developers except those at pH 11 and higher! Borax will dissolve quickly or slowly depending on crystal habit and water of hydration. That is why we are seeing differences here.

Actually, the best alkali for this pH would be TEA, but we have already seen the problems with differences there. I have used the Formulary TEA now for over 10 years with no problem. I talked to them about this and it is Photograde and is used by many other companies for photo products. There is a purer grade with a big jump in price.

You can force an alkali to work in a lower or higher range than what it wants to buffer in. It will work. BTDT. It just can move on you but if the developer is designed to work with this situation there is no problem.

An added thought. You have Ascorbate / Ascorbic acid there and that is a secondary buffer all in itself. If you use HQ then you have the HQ anion present along with HQ which is an acid. This forms a secondary buffer. It depends on the amounts you use.

PE

 

[Rudeofus]

I've dissolved Borax at room temperature, and it only took a few minutes to dissolve. The Borax available here in the USA is sodium tetraborate decahydrate. Is that what you've got? Anyway, I dissolved it at up to 9 g/L; perhaps you are pushing it higher, closer to the solubility limit.

Ron recommended much higher concentrations (>25g/l) and I am still stuck trying to dissolve 35g/l in a solution which already contains 40g/l sulfite. If this doesn't work out soon, I'll incrementally add more water and sulfite stock to make it dissolve at last.

I've resisted using Borax because of the ten water molecules on it. I'm designing a concentrate, and I'm unhappy enough with having two water molecules on some sodium metaborate. With five times as much water in it, my instructions will have to say, "Keep the concentrate hot until the steam stops forming condensation on your safety glasses."

Don't forget that while you have 10 water molecules per molar unit of Borax, you also have four times the boron, which means you end up with a much more favourable water ratio for borax, depending on metaborate hydration, of course.

 

[Photo Engineer]

If this will not dissolve, then dilute it slowly until it is fully dissolved at room temperature. Then you know the maximum concentration that you can use. You can then back calculate the concentration and then make up that "proper" solution again. This will tell you the maximum concentration of your concentrate and of your working solution if you choose to dilute it.

PE

 

[Rudeofus]

If I dilute this recalcitrant mix slowly, I'll end up with some odd ball concentration and risk another round of precipitation once I add further components to the mix. Instead I'll add just enough water and sulfite stock to reduce the borax level to 30g/l and 25g/l, sulfite concentration kept constant, of course. If buffering is really an issue, or if the experiment requires that buffering is optimal, I have no problem using 500ml on 135 or 120 rolls. Doubling the amount of soup and leaving the amount of film the same should have the same effect as doubling the buffer concentration (assuming good agitation).

I know, a commercial dev wouldn't get away with 500ml required for 135/120, maybe that's the rule we need to break to advance in performance.

 

[albada]

The pH of sodium sulfite drops quickly after mixing.
Initially, 2 grams of sulfite in 30 ml of distilled water has a pH of 9.9 to 10.0.
After about 20 minutes, the pH has dropped to 9.75 or 9.80. I confirmed this with two different batches of sulfite.
The odd thing is, after a developer is completely mixed, I haven't noticed a pH-drop in this time-frame. Perhaps ascorbic acid is protecting the sulfite.

Any idea what's going on here?
Does aerial oxidation of sulfite occur that quickly? Does it produce an acid which pulls down the pH?

That drop of 0.1 to 0.2 is enough to have a noticeable effect on activity. I'm tempted to mix in just a little sulfite at the start, add everything else, then add the remainder of the sulfite last.

Potassium sulfite is looking better than ever...

Mark Overton

 

[Photo Engineer]

Sulfite can oxidize to Sulfate which is a stronger acid and which can lower the pH. I am uncertain as to how fast this can take place though. That sounds to rapid to me. Also, it is common, when mixing developers, to add some or all Sulfite first to protect the developing agent which is added to the mix.

PE

 

[Rudeofus]

I'd like to put some perspective of what the pH difference reported by Mark would mean if it came only from conversion of sulfite to sulfate. If we use the pH calculator suggested by him, we use the following constant: 2g of anhydrous Na2SO3 in 30ml water is 1000/30 * 2/126 = 0.529 moles/liter. The following constants can be obtained from their respective wikipedia pages:

H2SO3: pKa1 = 1.857, pKa2 = 7.172
H2SO4: pKa1 = -3, pKa2 = 1.99
NaOH: pKb = 1

Using a concentration of 0.529 mol/l H2SO3 and 2*0.529 mol/l = 1.0582 mol/l NaOH yields a pH of 9.92, which is so close to Mark's measurement that I would be suspicious if a lab worker presented me that number. Now we can increase the concentration of H2SO4 at the expense of H2SO3 and see, how pH value changes.

If 1/4 of H2SO3 is converted to H2SO4, pH value lowers to 9.85.
If 2/4 of H2SO3 is converted to H2SO4, pH value lowers to 9.76.
If 3/4 of H2SO3 is converted to H2SO4, pH value lowers to 9.61.
If 4/4 of H2SO3 is converted to H2SO4, pH value lowers to 7.33.

Now, just for the sake of experiment, I simulated addition of H2CO3 to the mix, note that CO2 is part of air and will always dissolve in water to some extent.

Assuming that none of the H2SO3 is converted to H2SO4, the addition of

0.00001 mol/l H2CO3 lowers pH to 9.91
0.0001 mol/l H2CO3 lowers pH to 9.89
0.001 mol/l H2CO3 lowers pH to 9.66
0.01 mol/l H2CO3 lowers pH to 8.87

Note that 0.001 mol/l H2CO3 would mean only 0.044 g/l of CO2 dissolved in water. Total solubility of CO2 is, according to wikipedia again, 1.45 g/l.

From all this I would conclude that aerial CO2 going into the solution would be a more likely explanation of the pH shift than oxidation of sulfite.

 

[Photo Engineer]

Well, good answer. I discounted CO2 assuming that tap water or DW from the bottle would be saturated with air and thus CO2. Maybe it is a little of both, conversion to SO4 and absorption of CO2. IDK.

Your comment sounds reasonable.

PE

 

[Rudeofus]

Well, good answer. I discounted CO2 assuming that tap water or DW from the bottle would be saturated with air and thus CO2. Maybe it is a little of both, conversion to SO4 and absorption of CO2. IDK.

There is a good chance that Mark dissolved the sulfite in hot water or it would have taken forever. After it cooled down, it took in extra air, maybe more slowly than the cool down. After 20 minutes some equilibrium could have been reached.

If 1% of the SO3-- would convert to SO4-- in 20 minutes, SO3-- would not be used as preservative for developers and fixers, which should last at least a few weeks. A 1% decay in 20 minutes would equal a 50% decay after one day and a 99.4% decay after one week. Note that a 1% decay of SO3-- would not be noticeable with the pH meter.

 

[albada]

The odd thing is: The water was at room-temperature of 22-23C.
My distilled water has always been kept capped, so there's probably little gas dissolved in it.
I let the beakers sit overnight, and their pH's were 8.65 and 8.72 next morning.
In comparison, a test-developer I also let sit overnight went from 7.91 (at night) to 7.95 next morning. Its pH went up!

Anyway, I think I'll let some distilled water sit for hours to absorb all the gases it can, and then mix some sulfite and measure pH.

Mark Overton

There is a good chance that Mark dissolved the sulfite in hot water or it would have taken forever. After it cooled down, it took in extra air, maybe more slowly than the cool down. After 20 minutes some equilibrium could have been reached.

If 1% of the SO3-- would convert to SO4-- in 20 minutes, SO3-- would not be used as preservative for developers and fixers, which should last at least a few weeks. A 1% decay in 20 minutes would equal a 50% decay after one day and a 99.4% decay after one week. Note that a 1% decay of SO3-- would not be noticeable with the pH meter.