Acros 100 tidbits

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Lately I've been playing with Fuji Acros 100 a little; here's some tidbits.

I get EI 50 in D-76H 1:1 and EI 64 in other developers (more dilute) for about the same CI; that may be an artifact of using rotary agitation.

D-76H 1:3 gives a dead-straight curve shape.

Ilfosol-S 1:14 gives a rather strong shoulder above zone XI. This may be due to exhaustion but I don't believe it is; HP5+ in the same run gave a normal curve shape. More experience is needed, but that sort of shoulder could be useful. BTW, the Acros 100/Ilfosol-S pictorial "test" neg looks really crisp with fine detail; the best yet.

This run of HP5+ and Acros 100 is my first experience with Ilfosol-S, which I'd never paid any attention to but got to wondering about since it's a PQ/ascorbate developer and may give some of the advantages of Xtol without the disadvantages.

Rodinal 1:100 gives a straight curve shape out to zone XI, where it sweeps _upward_ fairly significantly.

The speeds and curve shapes mentioned resulted from N development; N+ and N- may be quite a bit different, as may results with intermittent agitation.

-- John Hicks (jbh@magicnet.net), July 22, 2001

Answers

John ; thanks for this interesting information. I'm not familiar with D76H - could you please explain? With Rodinal 1:100, was your EI 64? What time did you give for this dilution - I would guess about 20 minutes? Regards

-- fw (finneganswake@altavista.net), July 23, 2001.

> D76H - could you please explain?

D-76H:

Water 750ml 125F

Metol 2.5g

Sodium sulfite 100g

Borax 2g

Water to make 1.0L.

D-76H is a D-76 variant concocted by Grant Haist to elegantly avoid the problem of hydroquinone being activated as D-76 changes pH as it ages. Packaged D-76 is buffered to achieve the same goal. There's nothing otherwise special about it.

> With Rodinal 1:100, was your EI 64?

Yes, EI 64. 11'30"/68F with rotary agitation. I'd guess around 20-25% more time for intermittent agitation.

-- John Hicks (jbh@magicnet.net), July 23, 2001.


Since D76H has no hydroquinone in the formula you've given, how does it "elegantly avoid the problem of hydroquinone being activated as D- 76 changes pH as it ages"?

The reason hydroquinone is used in D-76 is that it is super additive with metol. Hydroquinone does not readily adsorb to the silver halide crystal except in a really high pH solution (10-11).

Conversely, metol easily adsorbs to the silver halide crystal but rapidly runs out of electrons. The hydroquinone is used to feed electrons to the silver halide crystal through the adsorbed metol molecules.

How does D-76H equate to this super additive chemical activity without the hydroquinone?

-- steve (s.swinehart@worldnet.att.net), July 26, 2001.


Please understand, I'm no chemist; I studiously avoided it in school...but here's my version of what happens with plain D-76 from people who I believe know.

At the freshly-mixed pH the hydroquinone serves to regenerate the metol but has virtually no reducing action itself. As D-76 ages, the pH rises and the hydroquinone becomes more active, thus causing an increase in resulting neg contrast.

For that reason, the packaged D-76 Kodak sells in the US is a buffered version that has about half the buffering of D-76d.

Grant Haist's solution was to simply omit the hydroquinone and increase the metol, giving D-76H about the same activity as D-76. My speculation is that although the pH also increases usually oxidation counters its effect and since there's no hydroquinone to "activate" the pH rise doesn't matter.

-- John Hicks (jbh@magicnet.net), July 27, 2001.


John. Since rotary processing usually uses less developer than inversion, when using Rodinal at 1:100, what volume did you use per roll? I use a JOBO processor for my film. Thanks

-- Jim Steele (jdsteele@hotmail.com), July 28, 2001.


> volume

250ml total solution per roll (actually 252.5ml per 80 sq in; you get the idea).

I know more solution is often recommended but that amount of solution has always worked ok in rotary and intermittent agitation for a long time and has given consistent results. If in doubt, though, use more.

-- John Hicks (jbh@magicnet.net), July 28, 2001.


Speaking of solution volume per roll, especially in the Jobo, I've found that 50ml D-76H stock per roll gives results indistinguishable from more stock, as does 2ml Rodinal stock and 18ml Ilfosol-S stock per roll. I usually use more solution than the minimum required to cover the film so I know I don't need to worry about running close to the edge of developer exhaustion, but all indications so far are that it isn't necessary.

-- John Hicks (jbh@magicnet.net), July 28, 2001.

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