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Monday, June 10, 2013

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.

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