The importance of pH and buffering question.

[Keith Tapscott.]

I just found a patent by L.C. Jones (1939) which seems to be about reducing variations of contrast in "M.Q. Kodalk" containing developers by substituting "Kodalk" with a carbonate. Would it be worthwhile trying this or a similar component combined with a borate to achieve greater buffering capacity?

http://www.google.com/patents?id=_TZKAAAAEBAJ&printsec=abstract&zoom=4&dq=2,165,797#PPA5,M1

 

[Photo Engineer]

Keith;

There is a difference between pH and buffer capacity and that is what is inherent in what you are asking.

What do you want to change? You can keep either constant and vary the other within limits. All 4 possible variations will give a different result in a given developer that is otherwise unchanged.

High buffer, but low pH will mute edge effects, high pH with low buffer will give higher edge effects. High pH and high buffer will give high contrast and muted edge effects. And that is just a generalization.

PE

 

[Keith Tapscott.]

Keith;

There is a difference between pH and buffer capacity and that is what is inherent in what you are asking.

What do you want to change? You can keep either constant and vary the other within limits. All 4 possible variations will give a different result in a given developer that is otherwise unchanged.

High buffer, but low pH will mute edge effects.

High pH with low buffer will give higher edge effects.

High pH and high buffer will give high contrast and muted edge effects.
And that is just a generalization.

PE

What I was wondering was the objective of what Jones did.
Was it to modify the developers for better buffering or to obtain some other effect?

 

[Photo Engineer]

Since they show no image structure data, such as grain or sharpness, and the results that they do show are rather foggy, I would say that their objective is obscure other than the use of a guanidine salt as alkali. Otherwise, the claims are pointless. And, the curves based on speed/fog seem to be rather ugly spelled with a capital UGH.

I would say that the patent is obsolete, and was probably never reduced to a practical developer.

PE

 

[Keith Tapscott.]

Would it be worthwhile trying this or a similar component combined with a borate to achieve greater buffering capacity?
http://www.google.com/patents?id=_TZKAAAAEBAJ&printsec=abstract&zoom=4&dq=2,165,797#PPA5,M1

If greater buffering with moderately low pH film developers means "muted edge-effects" then I wouldn`t want that. Thanks P.E. I`m glad it wasn`t just me who found the patent confusing.