Welcome, Rob!

From now on, this blog counts with another author, Rob, from Belgium, 57 years old, a little younger than me, I am 62.
I wish all the best to this work together, I could see many good things done by Rob in Flickr and now in Ipernity.
Welcome, Rob, feel confortable and post when you wish about what you want.

Cheers!

Understanding the expressions proposed

I have been talking, in the posts before this one about a possible mathematical description of developers. My last proposal was this one:

Agent2 = A x Agent 1
Alkali 1 = B - C x Agent 1
Alkali 2 = D - E x Alkali 1

Is there a meaning for the expressions? I think so, and let me explain why I choose these and not others. The first expression shows that there is an optimum relation between two complementary developers. It is known, for instance that Phenidone and Hydroquinone are in a relation close to 1:40, coffee and Vit. C in a relation similar to 1:2 and so on.

Then we know that each developing agent alone needs a certain pH to work well. One is more close to alkali 1 and the other more close to the alkali 2. If agent 1 increases, alkali 1 decreases and alkali 2 increases and vice-versa. In that is why I think that theses expressions serve to describe a family of developers. The developers of the same family must not work the same way, in general they increase activity as the amount of developers rises and maybe you get finer grain and low contrast with those that are less activ than with the others.

This is just a proposal to be analized by you, readers, and I am open for critics or for alternative proposals.

This proposal does not limit the choose and the research of new developers, it seaks for a little more order and choices. Let us assume that you select a certain family of 4 components with A,B,C,D and E of your criterious choice. You may then have several developers with the same ingredients but for different purposes: one is for low speed films, other to get finer grain, other to have more contrast and so on. Just give it a try and see if it works or not.

Introducing one more coefficient

Looking better to the expressions,

Agent2 = A x Agent 1
Alkali 1 = B - C x Agent 1
Alkali 2 = D - Alkali 1

I see that Alkali 1 in the last expression could include a multiplier coefficient, let as call it E. So, the generalized expressions should be written like this:

Agent2 = A x Agent 1
Alkali 1 = B - C x Agent 1
Alkali 2 = D - E x Alkali 1

The question now is to know why a general developer with two complentary agents should obey to these expressions. In the exceptional cases where the developing agents appear alone, they have an alkali combination that is better for it to work well. For instance, if you use just Metol, it works better with just sodium sulfite alone, that's to say, 0 g from sodium carbonate. If you use Hydroquinone alone it works better  with almost equal amounts of sodium sulfite and carbonate. Most Coffee developers use just sodium carbonate, maybe coffee works better with just sodium carbonate, and so on.

Let as see now how to find the coefficients for a particular developer. I will use here Reinhold G. Caffenol C-M recipe:

For 1 liter developer, we have:

54 g Sodium Carbonate

16 g Vitamine C

40 g Instant Coffee

Calculating the coefficients, A = Coffee/Vit. C = 2.5, assuming that Agent 1 = Vit. C and Agent 2 = Coffee.

If now we assume that Alkali 1 is Sodium Sulfite (0 g), B - C x 16 = 0 and Alkali 2 = D = 54. It is not possible to know the coefficient E, it is undetermined mathematically. It could be determined if we use another developer of the same family containing other amounts of sodium sulfite and carbonate.

So A and D are now fixed in 2,5 and 54. The equation B - C x 16 = 0 has a lot of solutions. If we fix however the maximum amount of Sulfite in 100 g/l, B = 100 and C = 6.25. E is not determined mathematically but assuming the approach that the sum of the amounts of alkalis is more or less constant, than E=1 (must not be).

We may then say that Reinhold's Caffenol C-M belongs to the family:

Vit. C, Coffee, S.S., S.C. = 2.5, 100, 6.25, 54, 1. 

Changing B, we have another different family that also includes this developer. Example, assuming that the maximum amount of sulfite is 120 = B, then C = 7.5

Vit. C, Coffee, S.S., S.C. = 2.5, 120, 7.5, 54, 1.

Describing developers with numbers

I have proposed in the last articles the description of a MQ developer using the expressions:

Hydroquinone = 1,82*Metol
Sodium Carbonate = 46 - 6*Metol

Sodium Sulfite = 100 - Sodium Carbonate

These expressions may be generalized like this, assuming that we use a pair of complementary developers and 2 alkalis in order to adjust pH.

Agent2 = A x Agent 1

Alkali 1 = B - C x Agent 1

Alkali 2 = D - Alkali 1

In this manner a family of developers may be said to be Agent 1, Agent 2, Alkali 1, Alkali 2, (A,B,C,D).

For quite a short time, I was told by Jay deFehr, here, that the optimum relation between Phenidone and Hydroquinone is 1:40. Assuming that we are using sodium sulfite and carbonate like for MQ developers, we could then write, choosing B, C and D with meaningful values:

Hydroquinone = 40 x Phenidone

Sodium Carbonate = 50 - 60 x Phenidone

Sodium Sulfite = 100 - Sodium Carbonate

The family of these developers would be then P, Q, SC, SS (40, 50,60,100).

One recipe taken from above expressions could be:

Phenidone - 0,1 g

Hydroquinone - 4 g

Sodium Carbonate - 44 g

Sodium Sulfite - 56 g

OK, a developer may have more things, but this is the nuclear composition that may work without more tweaks.

From now on, it is not a question of discovering a particular developer, but a family of them, related to the parameters A,B,C,D.

Disclaimer: I asssume that these considerations apply only to developers combining two developing agents and two alkalis.

Trust me, I am working hard...

Note: I made a mistake in the parameter used for Hydroquinone. Instead 1,28 it is 1,82 what is different. Although this is merely speculative, every MQ developer will develop with any amount or proportion and have their specific application. The number of recipes is endless, thanks God.

Aplying the equalities about which I spoke in the last article, I could produce following chart for general purpose MQ developers. Each of these developers will have a different behavior, from high to low contrast and the grain will be finer as the amount of sulfite is more and more greater than carbonate.

«Corrected data»

The data above can be better understood in the logarithmic graphic below:

«Corrected graphic»

It has a certain logic, when you think that developers containing only carbonate as alkali have about 50 g/Liter and developers containing only Sulfite have 100 g/ L. At the ends of the curves there is a discontinuity, we may have developers with only metol and sulfite and developers with hydroquinone only but with both sulfite and carbonate in almost identical amounts:

Examples:

1 Liter "Wall's Normal Hydroquinone", a lithographic developer, work solution:
50 g Sodium Sulfite
10g Hydroquinone
60 g Potassium Carbonate (or Sodium and the amount could be also 50g anhidrous)


1 Liter D23 of Kodak, a fine grain low contrast developer:

100 g Sodium Sulfite
7,5 g Metol

Disclaimer: The equations I proposed don't fit all and every general purpose developer, it is only an orientation. You may compose your developer with any amounts of the main substances, you may adapt the reasonings to other developing agents if you know the equivalence (Phenidone acts like metol but is 10 times stronger). Important is to know then what you get, how long the developer takes to develop and so on.

Final note: The equations used are now a little different, I introduced another condition, the sum of sulfite and carbonate should be constant:

Hydroquinone = 1,82*Metol

Sodium Carbonate = 46 - 6*Metol

Sodium Sulfite = 100 - Sodium Carbonate

Trust me, once I was an engineer...

Introduction

In this article I try to understand the rules behind the B&W developers, making use of some mathematical skills (while I still have them), having also in account that once I made much more complicated calculus, for instance with high voltage lines, electrically and mechanically. I can not do that anymore, I forgot everything, but here the equations are much easier to handle. This is only the first approach to the problem, more refinements will be done, this need some more time to treat data, although with help of 'modern technologies', understand computer.
I concentrate my attention only in developers MQ (Metol-hydroquinone) but the ideas may be used with other pair, if we know the equivalence to these two ones. For instance, Phenidone is said to be equivalent to Metol but 5 to 10 times stronger. When using Phenidone instead of Metol, we must reduce the quantity dividing by a number between 5 and 10.

---

With a certain dosis of patience I was regarding the quantities involved in MQ developers, Ilford and Kodak developers mainly. I filled a spread sheet with recipes and ordered the data by increasing Metol amounts. It was not that difficult to observe the graphics obtained with the amounts of the components, having the Metol quantity as the independent variable. I came to the conclusion that the main components like Hydroquinone, Sodium Sulfite and Sodium Carbonate may be calculated with following rules:

The amount of hydroquinone is in most cases 1,82 times the amount of Metol.
The amount of Sodium Sulfite is 11,5 times the amount of Metol plus 30g, the minimum amount that such developers have in general. The amount of Sodium Carbonate is 45 g minus 6 times the amount of Metol, it decreases as Metol increases. Finally the amount of Potassium Bromide has no exact rule, imho, just use an amount between 0 and 3 g/L. All quantities are given for 1 Liter developer, to be used indiluted.

I am not 100% sure, of course, whether these coefficients apply to most of the recipes, but I will discuss some examples:

The developer D76 from Kodak has this composition (see my source here)

Metol - 2 g
Hydroquinone - 5g
Sodium Sulfite - 100 g
Sodium Carbonate - 0 g
Borax - 2g
Potassium Bromide - 0 g

With my equations, I would have following developer instead:

Metol - 2 g
Hydroquinone - 3,64 g
Sodium Sulfite - 53 g
Sodium Carbonate - 33 g
Borax - 0 g
Potassium Bromide - 0 to 3 g

But, if I take the amount of Hydroquinone as base (5 g), then I have another recipe:

Metol - 2,75 g
Hydroquinone - 5 g
Sodium Sulfite - 61,6 g
Sodium Carbonate - 28,5
Borax - 0 g
Potassium Bromide - 0 to 3 g

The last one is perahps 'more like' D76 than the first, with more Sodium sulfite; the Carbonate of the second calculated recipe is, in D76, replaced by more sulfite and borax.

Another example is D23 from Kodak, the simpliest developer with only 2 components (see my source here):

Metol - 7,5 g
Hydroquinone - 0 g
Sodium Sulfite - 100 g
Sodium Carbonate - 0 g
Potassium Bromide - 0 g

Here we could say, according to the equations proposed, the developer would be:

Metol - 7,5 g
Hydroquinone - 13,65 g
Sodium Sulfite - 116 g
Sodium Carbonate - 0
Potassium Bromide - 1 to 3 g

Note: In both cases, No Sodium Carbonate appears.

Here we find a big difference in the amount of Hydroquinone. The high level of Metol, let us say, from 5 g/L upwords, makes Hydroquinone superfluous and lead to very fine grain developer but low contrast. On the other extremity, when Metol is zero, Hydroquinone must be higher than a certain threeshold, I think about 5 g/L is a realistic value but I found developers with much more than that and they are for high contrast but not fine grain or general purpose developers.

Now, let me give two more examples, that are more like the equations. Agfa/Ansco 40:

Metol - 4.5 g
Hydroquinone - 7.5 g
Sodium Sulfite - 54 g
Sodium Carbonate - 46 g
Potassium Bromide - 3 g

With the equations I propose, we would calculate pro liter:

Metol - 4,5 g
Hydroquinone - 8,19 g
Sodium Sulfite - 81,75 g
Sodium Carbonate - 18 g
Potassium Bromide - 0 to 3 g

These last two are not the same, but there is, maybe, another relation to be considered, if we see more in detail the sum of Sodium Sulfite and Sodium Carbonate in both is equal 100 g, more or less. This sum increases with the amount of developing agents, from about 80 to 100.

Another example is following, GEVAERT G.214:

Metol 2 g
Hydroquinone 3 g
Sodium Sulfite (anhydrous) 25 g
Sodium Carbonate 16 g
Potassium Bromide 1 g

Calculated:

Metol - 2 g
Hydroquinone - 3,64 g
Sodium Sulfite - 53 g
Sodium Carbonate - 33 g
Potasium Bromide - 0 to 3 g

Note: The relation Sulfite to Carbonate is the same in both, which leads, perhaps to the same pH.

Again the result is not totally identical. In fact, unless we use very complicated equations, it is not easy to describe all MQ developers with a unique set of simple equations. These equations may be used only as starting points for a new developer to be tested. They are more or less accurate for Metol varying between 1 and 5, not less and not higher than these extremes. Because the number of combinations is endless, I can not give any warranty for the success of developers following the equations proposed:

Hydroquinone = 1,82*Metol

Sodium Sulfite = 30 + 11,5*Metol

Sodium Carbonate = 46 - 6*Metol

For Metol = 1 to 5

This developer is a find!

I am talking about Caffenol Super Strong again. It is, indeed, a fine developer, specially for Black and White film. Today I exposed a 120 Shangai 100 ISO film and developed it with the same working solution I prepared one month ago. This solution developed until now 3 films and the developing time is still the same, I have been using 45 minutes but this time I used 60 minutes and it came out a little overdeloped.

I consider the developer as a fine grain developer, I can't see any grain and it gives a wide grey scale. The preserving properties are probably due to the presence of sodium sulfite. Remember that the working solution for film is:

700 ml water
20 g Sodium Sulfite
20 g Sodium Carbonate
1 g Potassium Bromide
20 ml of the stock solution CSS
Water to make 1 L

I will keep using the same solution until it is exhausted. Let us see how long it lasts.

I used an Agfa Synchro box today working with a macro lens instead of its lens. I thought it would give better results but no, only the central part is focused. But it gives a nice artistic effect.

Example 1

Example 2

Example 3

Example 4

Example 5

Example 6

Example 7

From 8 pictures, only one was not usable but it was my fault, the image was out of the right angle of view.

Note: If you analize well the images you will see, on their right side, some difuse numbers. The light could pass through the film paper by the numbers viewer and the developer revealed this very little grey density difference.