D-23, Microdol-X, D-76: Curves, Sulfite, etc.

[Ken Lee]

I have read that D-23 (not divided D-23, but D-23) is basically the same formula as Microdol-X. In these formulas, the main developing agent is Metol, while D-76 contains Metol and an additional developing agent, Hydroquinone.

They all rely on a considerable amount of Sodium Sulfite.

Do these developers produce an S-shaped densitometric curve with most films ? If so, why ? Does D-76 produce a more linear curve than D-23/Microdol ? If so, is it because of Hydroquinone ?

Compared to traditional films, are T-grain films less compatible with developers like these, which rely on Sodium Sulfite ?

Does the curve become more linear as theses developer are diluted (1:1, 1:3) ? Is that due to local exhaustion of developer ? If so, does that suggest that too much agitation reduces the compensating effect, and thus negate the benefit of dilution ?

Do these developers give lower film speed than other developers, which they trade for finer grain ?

I ask because I have been attracted to the simplicity of D-23, which has only 2 ingredients.

[Henry Ambrose]

If speed is not important I think you are correct. I've fooled around with D23 a bit and found it a nice developer. Its been a while though so I can only state a general impression.

[Drew Wiley]

The high amount of sulfite in D-23 acts like a silver solvent, so you sacrifice some
acutance; but this is a good choice for divided (2-tray) development. D76 gives better acutance. Curve shape at the top of the curve (the shoulder) depends a great
deal on the specific film. But with respect to the toe and middle part of the curve,
both of these tend to sag significantly. There are times when such a curve shape can be useful, but if you want a straighter line, HC-110, TMaxRS, or one of the pyro formulas would be a better choice. Straightness also depends on how far you expose
the film, and how to what level of contrast you develop it. With respect to 76, moderate dilution (1:1) does not seem to affect the curve shape a lot. I can't remember the effect with D23, since I haven't used it for a long time. An analogous developer which some folks like is Perceptol, which works well 1:1.

[BetterSense]

If speed is not important

That's the main reason I switched away from D23. I used to use replenished D23 pretty much exclusively until I started using Xtol and realized how much speed D23 was costing me. I still like it a lot...it was really in its prime in TX sunlight, on film that has been exposed 'generously'. It seemed to really tone down and smooth the highlights into something printable.

[Chuck P.]

But with respect to the toe and middle part of the curve,
both of these tend to sag significantly. There are times when such a curve shape can be useful, but if you want a straighter line, HC-110, TMaxRS, or one of the pyro formulas would be a better choice.

You're saying that with D-76, the toe and the middle of the curve sags significantly? I have not found that with D-76 and TMX as this combination is very linear in my tests.

I have longer toe and an upswept curve with TMX and HC-110.

[Oren Grad]

Does the curve become more linear as theses developer are diluted (1:1, 1:3) ? Is that due to local exhaustion of developer ? If so, does that suggest that too much agitation reduces the compensating effect, and thus negate the benefit of dilution ?

In principle a compensating effect should enhance any tendency toward a shoulder, thus making a curve less linear, not more.

[IanG]

This was Kodak's first Fine grain developer for 35mm stills camera use.

Eastman Kodak Research Fine Gran Developer 1927

For Fine grain. - A developer recommended by the Eastman Kodak Research Laboratories for use when images of specially fine grain are required is as follows:-

Metol . . . . . . . . . . . . . . . . . . 8 gr (2g)
Sodium Sulphite (anhyd) . . . . . . 400gr (100g)
Borax . . . . . . . . . . . . . . . . . . 8 gr (2g)
Water to . . . . . . . . . . . . . . . . 14 ozs *** (If US oz 1600ml - UK 1540ml)

The developer works more slowly than those of normal formula. - A.P., May 25, p. 504.

This seems to be one of the earliest published Fine Grain developer from Kodak. D76 was more specifically for motion picture processing (originally).

It's far more likely that the volume is US, particularly as the formula emanates from Rochester not Kodak Research, Harrow, but the difference is quite negligible. This formula pre-dates D76 and is quite similar to H76 and DK76 & DK76b, although more dilute.

Ian

[Ken Lee]

In principle a compensating effect should enhance any tendency toward a shoulder, thus making a curve less linear, not more.

Perhaps I have misunderstood. I thought that compensation gives a boost to shadow values, while leaving the high values less effected. This would lift the sagging toe of an S curve, no ?

[Ken Lee]

This was Kodak's first Fine grain developer for 35mm stills camera use.

Eastman Kodak Research Fine Gran Developer 1927

For Fine grain. - A developer recommended by the Eastman Kodak Research Laboratories for use when images of specially fine grain are required is as follows:-

Metol . . . . . . . . . . . . . . . . . . 8 gr (2g)
Sodium Sulphite (anhyd) . . . . . . 400gr (100g)
Borax . . . . . . . . . . . . . . . . . . 8 gr (2g)
Water to . . . . . . . . . . . . . . . . 14 ozs *** (If US oz 1600ml - UK 1540ml)

The developer works more slowly than those of normal formula. - A.P., May 25, p. 504.

This seems to be one of the earliest published Fine Grain developer from Kodak. D76 was more specifically for motion picture processing (originally).

It's far more likely that the volume is US, particularly as the formula emanates from Rochester not Kodak Research, Harrow, but the difference is quite negligible. This formula pre-dates D76 and is quite similar to H76 and DK76 & DK76b, although more dilute.

It appears that Anchell and Troop got things backwards: They write that D-23 was released by Kodak in 1941, as an improvement over D-76, which dates to 1927. They suggest that D-23 was introduced for the movie business.

I have wondered how a lower number (23) could supercede a higher one (76).

Which document do you quote for your formula ? Everywhere I have looked, D-23 is listed as containing 2 ingredients, as follows: 7.5 g Metol, 100g Sodium Sulfite, water to make 1 Liter.

(The 2-bath version - which I am not discussing - adds Sodium Metaborate (in the second bath). I am asking about D-23, not divided D-23.

[IanG]

Ken, I have various original Kodak publications with many of the formulae in, then also précis of various research papers published in magazines like the British Journal of Photography.

D23 & D25 were published at the same time in 1941, but it's part of the continuation of the earlier 1927 research.

Essentially D23 & D25 leave out the Borax so work at a lower pH, hence the need for more Metol, however the replenisher D25R contains Sodium Metaborate.

What's remarkable is just how many years Kodak spent getting from the early Fine Grain Developer (above) and D76 to D23/25 DK-20 and then Microdol.

I doubt Bill Troop was aware of the 1927 Kodak FG Developer when he wrote the FDC.

You can't read to much into Kodak's numbering system, you need to remember that often their early formulae came from companies they'd taken over or were clones of earlier formulae. After all both of Kodak's Research departments at Rochester (US) & Harrow (UK) were set up and led by Mees and his research staff from the UK company Wratten & Wainright.

It's possible that the initial work for D23 & D25 was done much earlier than 1941 because when Kodak had dichroic fogging issues with DK20 they went back to an earlier area of research for Microdol.

D76 itself is derived from an earlier Wellington & Ward Buffed Borax developer.

Ian