Pyrocat HD confusion?

I finally ran a test with Pyrocat HD. I got Photographers Formulary's 50 liter kit. I decided to mix a 100 ml stock solutions of part A and part B. So I mixed 75ml out of the bottle of both with water to make 100 mls each of the stock solution.

I needed 500mls of working solution so I mixed 2.5 mls of part A and part B which makes 5mls combined of stock somution. From that, I mixed 100 parts water (500 mls) to make 505mls of working solution.


I processed my Arista EDU 400 at 86 degrees F at 10 mins. Agitated for continuesly and 10 secs every minute afterwards. My negs came out thin. What went wrong?

Nearly all my films needed around 15 minutes with H-D 1+1+100 @20c. That being said, even the thin looking negatives printed very well. Looks like you mixed an incorrect ratio, (.5+.5+100) for 500 ml you should have mixed 5+5+500. I mix 5+5+450, then add enough water to make 500 ml.

Thanks Rick

Rick A said:

Nearly all my films needed around 15 minutes with H-D 1+1+100 @20c. That being said, even the thin looking negatives printed very well. Looks like you mixed an incorrect ratio, (.5+.5+100) for 500 ml you should have mixed 5+5+500. I mix 5+5+450, then add enough water to make 500 ml.

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Thanks Rick! I have a feeling that I was off. Good to have fellow APUGers to refer to. You have a Merry Christmas!

Don

I think Rick is right. You may find that 7.5:5:500 works better. You have a lot of options with this developer.
Juan

Mainecoonmaniac said:

....I needed 500mls of working solution so I mixed 2.5 mls of part A and part B which makes 5mls combined of stock somution. From that, I mixed 100 parts water (500 mls) to make 505mls of working solution.....

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I wonder if mixing the two stock solutions together first might have some effect. I've always added part A to the required final amount of water then part B. I think (not sure) that that is what the instructions say.

Persevere with Pyrocat. It's a superb developer.

It really should not matter in what order the two parts are added if it is done promptly just before use.

I always measure the water first, then add A and B to that. I'm not sure if you could mix A and B then put in the water. You definitely can add A to half the water and B to the other half, then mix.

What Rick said. Both to the proportions and to adding to the solution.

I measure A, put it in the beaker, fill the measuring graduate and empty it in the beaker 3 times to effectively get all of A in the beaker. Add about 1/3 of the water necessary. Then measure B, and do the same thing, then fill the beaker to where needed. That way, there is no accelerated activity between A & B. It's been a long time since I had chemistry in college, but intuitively it just "seems right."

There are some excellent chemists on this forum that could tell you for sure. I've learned a lot from them just perusing their posts.

Sound procedure, Stephen.

I once mixed A and B initially and the mixture turned dark immediately. Not sure if it is wrong, but it did not look good. Never did it again like this.

Lars

I have always mixed Pyrocat PC (in glycol) with the stocks first then add couple drops of LFN then the water. Never had a problem.

I've been using a hydroquinone version of Pyrocat-HD and always mix the A with the B then add to the water. Never any trouble, as you say. It shouldn't be any different with Pyrocat

Gerald C Koch said:

It really should not matter in what order the two parts are added if it is done promptly just before use.

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Thin negs may print ok. I use it for new cyanotype on XRay films. I measure out the water add A then B. The stain has more density in UV than you might expect.

I redid my test with everything the same except changing the dilution per Rick's suggestion and my negs look good. Gotta tweak the process a bit to suit my quirks. Thanks Rick Allen!

Gerald C Koch said:

It really should not matter in what order the two parts are added if it is done promptly just before use.

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It does with Pyrocat you'll oxidise some or even much the Pyrocatechin adding Part A to Part B.

Ian

Gerald C Koch said:

It really should not matter in what order the two parts are added if it is done promptly just before use.

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Mixing Part A to Part B without diluting Part A first will oxidise some or much of the Pyrocatechin so it's critical to dilute Part A first with around half the final volume of water.

This could be the reason for the thin negatives at a time/temp that show easily be OK.

Ian

Shouldn't it happen with hq also then? Or does it oxidize less readily?

Ian Grant said:

It does with Pyrocat you'll oxidise some or even much the Pyrocatechin adding Part A to Part B.

Ian

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It doesn't oxidise as redily (quickly).

Another issue is some have noted that the bottles used by the PF aren't high density plastic and you get oxygen passing into solution through the walls of lower density plastics, I know this is an issue with Prescysol a UK clone of Pyrocat HD.

Ian

It doesn't oxidise as redily (quickly).


Awesome. Another reason to use hq instead.

I always wondered why perishable solutions come in LDPE. Is it because the bottles are thicker/more sturdy?

Wayne said:

It doesn't oxidise as redily (quickly).


Awesome. Another reason to use hq instead.

I always wondered why perishable solutions come in LDPE. Is it because the bottles are thicker/more sturdy?

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It's because the LDPE bottles are much cheaper . . . . . . . I had some left fom an old job and stored Pyrocat HD in them thinking it would last longer split up over a number of small bottles. The reverse was true it had a short bottle life, I've had it last over 4 years (no glycol) in HDPE bottles.

The advantage of Pyrocatechin compared to Hydroquinone is its a fine grain developer in its own right and has better tanning/staining properties as well leading to better definition, edge sharpness, micro-contrast - better retention of very fine detail.

Ian

Ian Grant said:

The advantage of Pyrocatechin compared to Hydroquinone is its a fine grain developer in its own right and has better tanning/staining properties as well leading to better definition, edge sharpness, micro-contrast - better retention of very fine detail.

Ian

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Most of which is probably of minimal benefit even if true, when the smallest I shoot is 6x7 and the largest I usually print is 11x14.

What makes you say it has "better staining properties" than hq when by most accounts hq has been very little explored as a staining developer?

Wayne said:

Most of which is probably of minimal benefit even if true, when the smallest I shoot is 6x7 and the largest I usually print is 11x14.

What makes you say it has "better staining properties" than hq when by most accounts hq has been very little explored as a staining developer?

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Well I (and many others ) can see the benefits on similar sized prints from 545 & larger MF through to large format, in my case 5x4 & 10x8. Of course the benefits become even more apparent on large prints but most of mu exhibition work is just a little larger than 10x8 actually image size on the paper.

The staining properties of Hydroquinone are well known and have been exploited to a smaller degree because it's always been known to be much weaker than Pyrocatechin or Pyrogallol as is the tanning effect.

Ian

Ian Grant said:

Well I (and many others ) can see the benefits on similar sized prints from 545 & larger MF through to large format, in my case 5x4 & 10x8. Of course the benefits become even more apparent on large prints but most of mu exhibition work is just a little larger than 10x8 actually image size on the paper.

The staining properties of Hydroquinone are well known and have been exploited to a smaller degree because it's always been known to be much weaker than Pyrocatechin or Pyrogallol as is the tanning effect.

Ian

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Where are these well-known weaker properties written about? When you say you see the benefits of catechol stain (over hq's stain) does that mean you have tested both? The following table has been posted a number of times here, which shows that hq has a strong stain as pyro or catechol as long as sulfite is very low. This is the only published info I've seen so if there's more published or anecdotal info I'd like to read it. Another member I've pm'ed with found the stain stronger than catechol's (though he did not find that desirable..not sure if it was merely a stronger general stain). I am not a qualified tester, I'm just a dabbler. The discussion of why there isn't more info or research on q staining developers always seems to end in speculation that the stain isn't as durable or useful or some other speculation but it's always speculation. I haven't read the article cited below but I probably should.

Does anyone have the full citation? This was excerpted from L P Clerc's Photography Theory and Practice, 1971


"(Lumière and Seyewetz, 1928) shows the colour of the secondary image obtained in various developers, its relative intensity and the concentration of sulphite necessary to prevent its formation.

Developer -- colour -- relative intensity -- sulphite g/litre

Pyro -- yellow-orange -- 10 -- 11
Catechol -- black -- 10 -- 6
Hydroquinone -- yellow-brown -- 10 -- 2
Chlorhydroquinone -- yellow-brown -- 10 -- 2
Amidol -- reddish-brown -- 8 -- 2
p-Aminophenol -- brownish-black -- 3 -- 2
Metol -- brownish-black -- 2 -- 1
PPD -- Grey -- 1 -- 0
Glycin -- None."