• Welcome to Photrio!
    Registration is fast and free. Join today to unlock search, see fewer ads, and access all forum features.
    Click here to sign up

Dektol vs D72 (My Observations)

Philippe-Georges said:
BTW, what's really the difference between the two in the working?
Click to expand...

I have been able to successfully replenish DS-14 developer with the stated replenishment formula, that is, standard developer without Potassium bromide; therefore a batch of developer can be kept going with high quality results for an extended period of time.
 

What is the replenishment rate?
 

I mean the difference between Dimezone-S and Phenidone as a working agent in the developer...
 
Philippe-Georges said:
I mean the difference between Dimezone-S and Phenidone as a working agent in the developer...
Click to expand...

AFAIK there won't be any meaningful difference. Apart from the keeping qualities as a stock solution, they are pretty much the same thing.
Even the supposedly poor keeping qualities of phenidone are IMO overstated. I keep around a stock solution of phenidone in glycol and this easily lasts more than a year without any form of deterioration. In water, it's probably a different story, but in that case dimezone-s wouldn't be safe against oxidation either.
 

I don't have any idea what French hardness measures (presumably calcium, but on what scale?). Presuming you mix your stock solution with distilled or deionized water, pH is the only thing you likely need to worry about on dilution, and you can pretty easily test for the change in development time, as long as your water doesn't change pH seasonally. In general, you want to expose a sheet of paper without a negative, enough to give a full black, cut it up, and develop for increasing amounts of time until you stop seeing a change in the density, then develop for that period. In other words, print develop is generally carried to completion or very near completion.
 
Donald Qualls said:
pH is the only thing you likely need to worry about on dilution, and you can pretty easily test for the change in development time, as long as your water doesn't change pH seasonally
Click to expand...

Even with rather wild swings in pH, tap water is never buffered to such an extent that a mixed developer will vary noticeably in pH and hence activity. Even if it turns out to be very hard, buffering capacity is very very weak. Maybe for color (C41 CD/E6 FD) processes where you need to nail pH within +/-0.05 or so, this *might* be something to watch out for, but in B&W and particularly print processing, water hardness is of no concern.

The other point of metal ions and in particular iron can be highly relevant when using vitamin C/ascorbate developers in the context of the Fenton reaction.

PS: French degrees of hardness translate into 10 ppm or 10mg/L CaCO3 per degree, so 3 degrees would be 30 mg/L or 30ppm. This would qualify as rather soft water and have a negligible impact on developer pH. From the translation it's not immediately clear to me if this is the actual hardness of the (tap? bottled?) water used by @maxpina or that it's the ideal hardness prescribed by some manufacturer. If it's tap water, I would find this rather surprising in an Italian context due to the prevalence of limestone. I'd expect most of Italy to get pretty hard tap water.
 

Yes @koraks , perhaps I have not explained myself well ..., the water I use to dilute the stock solution has a pH of 7.4 a fixed residue of 24.7 mg / l so very few dissolved salts, in fact it has 1.3 ° of hardness (13 mg / of CaCO3) almost nil, I would like @Donald Qualls to explain to me how to do the complete blackening test of the print to evaluate the right immersion time, I would be grateful.
 
Philippe-Georges said:
I mean the difference between Dimezone-S and Phenidone as a working agent in the developer...
Click to expand...

Over the last 15 years I have collected comments from the web about the differences between phenidone and Dimezone-S. I use Dimezone-S in several formulas (Pyrocat-HD, Pyrocat-HDC and ID-68 and ID-78). I have tried both phenidone and Dimezone-S in Pyrocat-HDC and I can't tell the difference (Zone type in-camera tests, monochrome densitometer), but Sandy King, who developed the Pyrocats, did write here, on the subject of the difficulty of weighing tiny amounts of phenidone, that within a range it didn't make any appreciable difference (from 1.5g/L to 2.5g/L where the formula requires 2g/L).

Various writers have suggested:
■ just use the same amount of Dimezone-S as phenidone, or
■ adjust for molecular weight (for Dimezone-S use 1.26 times the weight of phenidone), or
■ use a bit more than that (old thread at pure-silver, possibly searchable?) because Dimezone-S is "something like" "75% as strong." or
■ it depends on pH (also an old pure-silver thread) and how concentrated the developers are (like comparing Pyrocat which is very low concentration, high pH with ID-68/Microphen which is a higher concentration at lower pH). With the very dilute developers the difference between Dimezone-S and phenidone was greater. I don't know how good their testing was but they did seem to have made an effort.

So after trying to digest all of that, I substitute 1.26g of Dimezone-S instead of 1g of phenidone and it works well.
 
Last edited:
You must log in or register to reply here.
Menu
Log in
Register