How Do Pyrocat-HDC A:B Ratios Change Developer Behaviour?

I often do Extreme Minimal Agitation with Pyrocat-HDC mixed 1.5:1250 or 300. I initially agitate continuously for 90 sec, and then 10sec at 11- and 21min, with a total time of 30 min.

I get quite good results with this, but my EI is about 1/3-2/3 stop slower than box speed. This unlike semistand where I only agitate at the beginning, and then again at the midpoint, and get full box speed, presumably because of the much longer total time with semistand - 45-60min being typical.

For most films, the slight loss of speed with EMA doesn't matter. Where I do care, though, is with slower films like Agfapan APX 100 or Ilford FP4+. These already slow films start to require lens openings and shutter speeds at a degraded EI that I'm not crazy about.

So, does increasing the concentration of either part A or B, make -HDC more active and thus crank up effective EI? For example, if I did 1.5:1.5:250 would I see an effective speed more likely to be closer to full box?

I plan to test this, but wondering if anyone else has any experience or wisdom in the matter.

This is a developing story ...

I am interesting in knowing if there is any way to increase the contribution of the imagewise stain to the density of the negatives. Is there a stain-on-steroids mode where most of the image density comes from the stain? Not interested in bleaching and redeveloping a few times to get more stain.

Raghu Kuvempunagar said:

Is there a stain-on-steroids mode where most of the image density comes from the stain?

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Two obvious routes come to mind:
1: Reduced agitation + prolonged development. This tends to result in a higher stain:silver image ratio than with shorter development times. Base stain will remain low if you keep within sensible time limits, suggesting that it's not overall stain you end up with, but proper image-wise stain.
2: You say you're not interested in bleach & redevelopment - then how about just bleach? You can bleach out the silver image, ending up with just the stain image.

I assume #1 is the more appealing option for you. In a similar vein, I suppose you could work out an optimum developer configuration that will create the most image-wise stain while keeping general stain low. I'd expect this happens if you set the developer at the point of exhaustion, so a low A vs. high B ratio. This will be a balancing act together with development time. I expect you'll get to more or less the same point of a somewhat higher A:B ratio and a longer development time vs. a lower A:B ratio and a shorter development time.

chuckroast said:

I plan to test this

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Looking forward to the results; sadly, I can't offer any concrete advice other than that if film speed is critical, I'd move to XTOL or one of its clones. You'll also get very fine grain that way.

When you compare semi-stand with EMA are your Pyrocat proportions the same in each case?

I have only used the standard 1:1:100 (but my Part_B is a bit weaker apparently due to carbonate being maybe partly hydrated, but that's another story). I have always wondered why some people reduce the Part_B to be less than the Part_A, I suppose less accelerating alkali leads to lower activity leading to longer contact with the tanning agent in Part_A.

Steve Sherman writes (https://unblinkingeye.com/Articles/RASS/rass.html)

• Normal contrast negatives PyroCat HD 1A + .66B + 175 water
• PyroCat HD part B is reduced by 33 % to combat dichroic fog with extended development times

<end of quote>

He uses Ilford sheet films if that makes any difference, and his dilution rate is the same as your 1.5:1:250,

so if you increase the part_B to equal the Part_A might dichroic fog be a problem? I have never seen such fog or probably wouldn't recognise it anyway.

Maybe bumping up the Part_A could increase film speed by increasing the developing agents? I'm not going to do exhaustive tests but I will try that.

john_s said:

When you compare semi-stand with EMA are your Pyrocat proportions the same in each case?

I have only used the standard 1:1:100 (but my Part_B is a bit weaker apparently due to carbonate being maybe partly hydrated, but that's another story). I have always wondered why some people reduce the Part_B to be less than the Part_A, I suppose less accelerating alkali leads to lower activity leading to longer contact with the tanning agent in Part_A.

Steve Sherman writes (https://unblinkingeye.com/Articles/RASS/rass.html)

• Normal contrast negatives PyroCat HD 1A + .66B + 175 water
• PyroCat HD part B is reduced by 33 % to combat dichroic fog with extended development times

<end of quote>

He uses Ilford sheet films if that makes any difference, and his dilution rate is the same as your 1.5:1:250,

so if you increase the part_B to equal the Part_A might dichroic fog be a problem? I have never seen such fog or probably wouldn't recognise it anyway.

Maybe bumping up the Part_A could increase film speed by increasing the developing agents? I'm not going to do exhaustive tests but I will try that.

Click to expand...

I typically use 1.5:1:250 as my baseline dilution for both EMA with both Pyrocat-HD and -HDC. (HDC seems to very slightly decrease the CI but not a whole bunch and not enough that I've much worried about it.)

The real difference is baseline agitation and time:

• For semistand, I agitate continuously for 2 minutes, 15 seconds at 31 min, and end at 60 min at a nominal 68F.
  
  
• For EMA, I agitate continuously for 90 secs, and 10 seconds at 11min and 21 min, and end at 30 min at a nominal 68F.

But I can- and do vary this based on a variety of factors:

• Film Type: FP4+ likes a little more exposure (i.e., an EI lower than box speed), maybe a bit more dilution around 1.5:1:300 and a bit more time in the 35 min-ish range. Tri-X (TXT) needs 45-ish minutes of EMA, so does Fomapan 200. In fact, I just started carefully considering FP4+ and that's what prompted my question here.
  
  
• All the films I have tried respond well toe 60min semistand, but in higher SBR settings, this can lead to very dense highlights. The detail is there, thanks to the semi-compensating nature of Pyrocat, but if you don't have clean burn boundaries, it can be tricky to print these.
  
  
• Short SBR: Short, low contrast scenes can be enhanced with a dilution of 1.5:1:200 and doing EMA for 45 min to an hour. Very short SBRs can be further enhanced by doing 3- or 4- agitations during the EMA total time rather than just 2.
  
  
• Long SBR: Handled by increasing dilution and/or reducing time, though I always do the initial agitation as described above. You have to be careful though. High dilution can make the developer so acute that the grain becomes pronounced, especially in 35mm. Moreover, there is a limit of how far you can go with this. If you dilute too much, the developer loses its effectiveness entirely.

I have seen some fogging with hour long semistand with Tri-X, but I like the overall effect enough to live with it and correct it with split VC printing techniques as I am 100% wet silver printing all this.

How you render the negative matters. I use a VC cold light head that is inherently lower contrast than a condenser head. For this reason, I like my negatives to have more contrast. That's why I've tended to end up more in the 45-60 min range for this. Steve Sherman is contact printing and has shifted to lower contrast negatives. His EMA is more like 30 minutes as I recall. I would imagine digital scanning would have its own demands in this regard.

I suspect raising the amount of Part B will make the developer more active because you're raising the alkalinity. I suspect that raising the porportion fo Part A will increase staing. I need to actively pursue these theories, but my real life keeps getting in the way...

P.S. Tri-X is not Tri-X is not Tri-X. TXT in 4x5 has a long toe and needs a decent exposure to get going. This moves everything up the H/D curve and can make highight managment tricky in a high SBR setting. 400TX in 120 and 35mm is a horse of a different emulsion, with a much shorter toe that responds to light earlier in the H/D curve. You have to consider this when figuring out exposure, placement, and development. Since I don't particularly like staring at my densitometer for hours, I just make multiple exposures to take these factors into account as sort of educated guestimations. My interest isn't in some analytical understanding of what's going on, but whether or not I am getting printable negatives.

john_s said:

I have always wondered why some people reduce the Part_B to be less than the Part_A, I suppose less accelerating alkali leads to lower activity leading to longer contact with the tanning agent in Part_A.

Click to expand...

To my understanding, reducing the proportion of Part B is primarily done for the purposes of: 1) allowing for longer development times, which theoretically contribute to higher acutance; and 2) reducing the amount of non-image (i.e., overall) stain.

In Pyrocat-HD, Part A contains the developing agents (primarily pyrocatechin and phenidone, plus some sodium metabisulfite and potassium bromide thrown in as preservatives, etc.) while Part B contains the activator (potassium carbonate). It's primarily the pyrocatechin and phenidone in Part A that control the intensity of development (i.e., the intensity of reduction of silver halide and the formation of image-specific stain). By comparison, Part B primarily controls the speed at which Part A works. Part B is also what contributes to the production of non-image (i.e., overall) stain. The two parts work synergistically, of course -- so, for example, Part B also contributes somewhat to the intensity of development alongside Part A -- but its role in that regard is secondary.

The reason users often use a reduced amount of Part B is to reduce the amount of overall stain. Since this stain doesn't generally contain useful information, it can be a bit of a nuisance, depending on your end use.

Choosing how to adjust the proportions of Parts A and B depends on what problem(s) one is trying to solve. My simplistic rules-of-thumb are:

a) If your negatives are thin and/or flat, and increasing development time isn't an option for you (e.g., because you're worried about getting too much base stain), increase the proportion of Part A.
b) If you're happy with contrast and density but want faster development times, increase the proportion of Part B (with the caveat that you'll likely get increased base stain as an unintended consequence).
c) If you're happy with contrast and density but want less overall stain, reduce Part B (with the caveat that you may need to increase development time to compensate for the loss of activity in Part A).

It's also important to keep in mind that their needs to be sufficient Part A in the tank to adequately reduce the amount of silver halide present in the exposed image. Increasing Part B and/or extending the development time can't, by themselves, compensate for inadequate Part A. As I recall, Sandy King recommended at least 3 mL of Part A per sheet of 8x10 (and the same for one roll of 135-36 or 120).