Separating alkali from developing agents?

Hi,

A few possibly silly questions from a non-chemist to the chemists:

For those who brew their own MQ developer, does it make sense to mix two separate baths, one that contains metol, sodium sulfite, hydroquinon (and possibly potassium bromide), and another that contains only the alkali, and then mix them just prior to development? Would the storage life and working characteristics of two separate baths be better/more consistent compared to a single bath?

The reason I’m asking is, the Anchell&Troop cookbook claims that the activity of the published D76 formula that contains both metol and hydroquinone is variable over time due to a rise in alkalinity. I’m wondering whether separating the alkali as described above would prevent this problem?

I’ve tried D76H (the version without hydroquinone) and found that it is visibly less active (thinner negs) than regular D76. Hence my desire to pursue the MQ combination.

Also, is the variability in activity (due to PH change) of D76 pertinent to all MQ developers? E.g. Adox MQ Borax or Agfa/Ansco 17? Adox MQ Borax has 4g of Borax instead of 2g in D76. Would the larger borax content prevent a PH change during storage?

It is the Beutler formula, where two separate baths mixed just prior to development, that made me think it could be adapted to all developers.

Please note that I’m not talking about two bath development. I’ve tried that line and didn’t find a visible advantage.

Regards

What Anchell says is true but not a serious concern. People use D-76 in a replenished system for months without any problem. And yes it applies to low alkalinity MQ developers for film.

D-76H should have the same activity as D-76. But it is intended to be used as a one shot and not replenished. Note that the Metol content is slightly higher than for regular D-76.

The Beutler formulla can be made as a single solution if oxygen is excluded from the solution. Tetenal did this by supplying Neofin Blue in a sealed glass ampoule. This isn't really practical for the average user hence two solutions. A similar developer Ethol TEc was supplied as a single solution in an ordinary bottle However once opened its life was rather short.

Everything considered dividimg a developer into parts really doesn't get you much. Kodak gives the shelf life of stock D-76 as 6 months. Always determine how much you mix based on how much you will use in this time period.

D76 is a marvellous developer and suggest you trust in the fact that the Kodak team, with combined chemical expertise, knowledge and experience know what they are doing.

I don't think you will ever have a problem mixing developers as you suggest, i.e., making a stock solution A with everything minus the activator(s) and a stock solution B with the alkali (carbonate, metaborate, etc., etc.) and then combining the two just before developing. Many developers are formulated to be used exactly this way.

Those that aren't aren't adversely affected by being mixed fresh just before use (except the possibility of undissolved particles...). The real question, I suppose, is whether dividing the stock solutions will get you any real increase in shelf life. That would have to be tested. As for eliminating the slight increase in activity of D-76 when it ages, this should do the job splendidly.

Best,

Doremus


www.DoremusScudder.com

Hello,
if you separate the development substance together wit sodiumsulfite from the alkali (Borax) you have nearly the formula of a D-76 2-bath developer. The life time of solution A is very long without the borax and is determined mainly by the carry out of a small volume with each film. The oxidation of hydroquinone and metol by air is faster at higher pH values. There are many formulations in the old literature based on stock solutions.

Sodium Bisulfite is known to be a preservative of metol (it's in part A PMK Pyro) and of hydroquinone (it's used in certain skin lightening creams for this purpose).
So if the metol and hydroquinone was dissolved in sodium bisulfite solution to make part A and the other ingredients in part B in theory a long lasting two part D-76 looks possible to me.
But AFAIK nobody ever did the calculations and experimentation that would be needed.

The acidity of sodium bisulfite would have to be taken into account.

Considering the long shelf life of D-76 why are people trying to solve a non-existant problem. If you cannot use up a liter of developer in 6 months then why are you doing wet photography?

Basically it's because if you can make a liter of developer last 2 years you have a choice of 4 different, rather than one lasts 6 months.

Alan Johnson said:

Basically it's because if you can make a liter of developer last 2 years you have a choice of 4 different, rather than one lasts 6 months.

Click to expand...

OK but then the question becomes "If you cannot use up 4 liters of developer in 24 months then why are you doing wet photography?" (Before anyone jumps in, who has not read the complete thread, this thread is not discussing replenished systems.)

The shelf life of D-23, which contains no added alkali like boxrax, is the same as that for D-76. So mixing up two solutions with the borax in one and the rest of the chemicals in the other doesn't provide any advantage.

Forgive me but I don't see any real problem. Most people can mix up a batch of D-76 in less than 30 minutes. This includes the time to get the balance and chemicals off the shelf and cleanup afterwards. It's not rocket science. Just mix up what you think you will use in 6 months. Be that a liter or a gallon.

Jerry,
You have a good case re D-76, since it's pretty similar to Xtol, which I make last > 24 months by mixing in 10 500ml sealed bottles and it's not worth doing the work to make D-76 last >24 months.
But generally, and I'm sorry, I didn't explain what I meant very well,it is an advantage to have long lasting developers as many can be made up to choose from ,eg, alongside this solvent developer Xtol occasional amounts of other developers can be used provided they last >24 months.
So one can have a choice of Xtol, Rodinal,PMK Pyro and anything else can be made to last, I have used quite a few.Having a collection of long lasting developers is not strictly necessary but it makes film developing more interesting IMO.Anchell and Troop wrote a book about it.

It's interesting that Kodak spent many years of research into improving D76 but they were stuck because it had become a standard with clones from many other manufacturers. Initially a cine film developer the industry required it's availablity around the world. Later it became a mainstay of professional labs asa well. Kodak did alter the buffering and it's almost certain Ilford did the same.

The misnamed non Kodak D76H, (there was already a Kodak D76h MQ variant of D76), is really Haist alluding to the earlier (there was a url link here which no longer exists)

It used to be common to publish some formulae as one part or alternative much longer lasting 2 part solutions with the alkali in Part B.

Sodium mmetabisulphite is used in some powdered developers to help protect the developing agents in powder or lquid form, this form should be used rather than the less powerful (antioxidant) form Sodium Bisulphite, it should also be reasonably fresh. It's used in a couple of Ilford powder developers.

Ian

Hi Alan,

Having a collection of long lasting developers is not strictly necessary but it makes film developing more interesting

Click to expand...

Ah, but one must avoid the sense of "interesting" as in the Chinese curse, "May you live in interesting times."

There is also Ansell Adams' advice to thoroughtly learn one film and one developer before doing anything else. I currently use two developers, a Rodinal clone and HC-110. Over the years I have come to understand their benefits and problems. Both of these have a very long shelf life as a single solution. When using Ilford Pan-F I will add D-23 to tame this films contrast. I only mix what I will need.

Your point of using multiple bottles is a good one and one often overlooked. You cannot have oxidation in the absence of oxygen. By avoiding partially filled bottles much of the problem is solved.

Cheers from sunny Florida.

Jerry

I might add to Ian's comment about Kodak being stuck with D-76 that when they chose to make a new developer intended for commercial processors (HC-110) this new developer had to duplicate as nearly as possible the results from D-76. They still couldn't get away from D-76!

This developer would also solve the OP's problem. It lasts a long time (years) and is cheap. You can use it as a one shot diluted just before use. Easy and no mixing involved.

Gerald, you mention D23, have you tried D25 ? As you know it's the same except it has Sodium Metabisulphite.

At a lower level it would have less affect on the pH, but still act as a preservative.

Ian

Michael R 1974 said:

Isn't it Sodium Bisulphite (Bisulfite) in D-25?

Click to expand...

Depends which company publishes the formula, EK use Bisulphite, Kodak Ltd Metabisulphite. it more about the purity of the Meatbisulphite it seems to be manufactured differently in Europe, Kodak Bisulphite is a lower grade mixture of Bisulphite and Metabisulphite.

In some formula the differences are not so important but as a preservative then it becomes more critical.

I used Metabisulphite industrially and there was a significant difference, JT Baker produce and sell both, and the usage depends on how strong an anti oxidant is needed.

Ian

Sodium metabisulfite Na2S2O5 can be thought of as a chemical container for sulfur dioxide. When added to water 1 mole reacts with 1 mole of water to form two moles of sodium hydrogen sulfite (sodium bisulfite). It is used because it is more stable as a solid than sodium bisulfite. The most common form of sodium bisulfite is therefore a near saturated solution known commonly as bisulfite lye.

Ian, I tried D-25 many, many years ago but the development times were just too long. In a replenished system there was also significant sludging. At a lower pH its keeping properties are probably better than those for D-23.

Gerald C Koch said:

This developer would also solve the OP's problem. It lasts a long time (years) and is cheap. You can use it as a one shot diluted just before use. Easy and no mixing involved.

Click to expand...

Thank you all for the discussion.

Gerald, I don't have a problem. I've been a happy user of ID11 for many years and I go through 5 liters fairly quickly. I was just curious about the "problem" Anchell&Troop mention about D76 (i.e. rise in alkalinity and activity) and wondered whether there might be a solution. Personally, ID11 has always worked consistently for me.

Recently I've started experimenting with home brews (simple MQ developers really) and after reading this: http://www.udmercy.edu/crna/agm/phenvitc.htm and seeing how the activity of commercial D76 remained fairly consistent over many months, I concluded that Kodak must have changed something in the original formula for improved consistency. So, if I *did* use the original formula, would I run into the "problem" said to be discovered by Haist in the 1920's and discussed by Anchell&Troop, was the motivation for my initial question.

Regards

The Anchell & Troop book may be a bit alarmist about the D-76 problem. While the oxidation of hydroquinone causes an increase in pH with an increase in acrivity of the developing agents this is counter balanced by the loss of some of the hydroquinone with a decrease in activity. So the two effects balance each other out. Remember replenished D-76 systems can be used for long periods of time. The only limiting factor is the increase in bromide released during development.

Hydroquinone is unlike other developing agents in that its oxidation product the hydroquinone monosulfonate ion is also a developing agent. Albeit a weaker one. In fact Kodak sold the potassium salt as Balanced Developing Agent #1 for many years to season new batches of MQ developers.