Catechol/Pyrocatechin Developers

A broken ankle and six weeks enforced inactivity led me to

investigate a few questions that had crossed my mind, primarily is

there a difference in pyro and catechol/pyrocatechin developers? To

preface I have used pyro in various forms for many years in large

format, mostly 8x10 or larger, recently I have used Rollo Pyro/ABC+

and find that with various dilutions I can achieve almost all that I

desire. I had tried Pyrocat-HD, but experienced fairly high fog

levels and since I did not need the putative speed, I abandoned it

quickly.

 

To start I ordered catechol/pyrocatechin from two sources, they

arrived one appearing grey and the other dark brown, I pulled out

some catechol/pyrocatechin from Lauder Photographic ( my dye transfer

process days) that was almost 20 years old, and this was white. I

mixed a basic catechol/pyrocatechin developer from all three and

developed test wedges. The old Lauder and the grey

catechol/pyrocatechin developed to the same density, but the brown

catechol/pyrocatechin did not reach the same density on several runs,

so I discarded this product.

 

I next experimented with variations of catechol/pyrocatechin

developer with additional developing agents on hand, phenidone,

metol, and glycin. I could achieve much the same results with

variation of these agents, with the exception that phenidone and

catechol/pyrocatechin seemed to have a higher amount of fog. I used

variations of Potassium Carbonate or Sodium Hydroxide as alkali.

 

In the middle of this process I obtained access to a colorimeter, and

analyzed pyro (Rollo pyro) and catechol/pyrocatechin

(catechol/pyrocatechin alone, and with glycin, metol, or phenidone)

negatives, there was no significant difference in the absorption

spectrum between negatives developed in the two different agents.

(When I say significant, this is in reference to the published

spectral response of photographic papers, do not have a spectral

response for hand made platinum papers.)

 

The most significant fact I noticed in these experiments was that I

could not obtain a stain with catechol/pyrocatechin that was more

than 2/3 to 1 stop higher on UV/blue channel than using the visual

channel on a densitometer. This effect was independent of alkali or

additional developing agent. I could obtain as much as 2 stops or

more difference in density with pyro negatives between visual and

UV/blue channel densities.

 

In printing both step wedges and negatives on various papers, azo,

platinum, variable contrast, I attribute any difference in results to

this difference in maximum UV/Blue density between pyro and

catechol/pyrocatechin negatives, not to any particular difference in

the type/color stain of the two.

 

A nice developer

 

Catechol/pyrocatechin 100mg

Glycol 2-5 mg

K Bromide 1mg

K Carbonate 10gm

Water to make 1000 cc

Adding Metol .025mg did increase speed without increasing fog not

sure you need the K Bromide other than for fast films.

 

Most films 7-9 mins (rotary processing)

 

I now have several questions for members of this forum:

 

Has any one achieved higher differences between visual and UV/Blue

channel densities with catechol/pyrocatechin, and if so using what

developer/technique? I actually used three different densitometers to

validate my findings.

 

Is the tanning effect of catechol/pyrocatechin greater than pyro, and

does this limit the stain of catechol/pyrocatechin versus pyro? Is

there a method to limit the tanning effect?

 

I am not a photo chemist; I have not exhausted the topic in any

manner, but any suggestions for future enquiry?

Typo in my post Glycin not Glycol under nuce developer!

Russell,

 

Since you posted your question to the newsgroup and here I will answer respond here as well.

 

You wrote:

 

> A broken ankle and six weeks enforced inactivity led me to investigate

> a few questions that had crossed my mind, primarily is there a

> difference in pyro and catechol/pyrocatechin developers?

 

I have been using staining developers, including formulas based on both

pyrogallol and pyrocatechin, for many years, and have a few comments to

your questions.

 

>I had tried Pyrocat-HD, but experienced fairly high fog levels and since I

> did not need the putative speed, I abandoned it quickly.

 

I developd the Pyrocat-HD formula and it is used today by a fairly large

number of alternative printers who switched to it from either PMK or Rollo

Pyro. I don't know how to explain the high fog levels that you experienced

but the primary reason people tell me they switched from these other

developers is due to the fact that they get lower general fog levels with

Pyrocat than with either PMK or Rollo Pyro, and all of my tests certainly

confirm this.

 

 

I could achieve much the same results with variation of these

> agents, with the exception that phenidone and catechol/pyrocatechin

> seemed to have a higher amount of fog.

 

This has not been my experience at all. However, it should be noted that

phenidone must be used in very small quantities, perhaps about 1/100 the

amount of metol in the same formula.

 

 

 

> The most significant fact I noticed in these experiments was that I

> could not obtain a stain with catechol/pyrocatechin that was more than

> 2/3 to 1 stop higher on UV/blue channel than using the visual channel

> on a densitometer. This effect was independent of alkali or

> additional developing agent. I could obtain as much as 2 stops or

> more difference in density with pyro negatives between visual and

> UV/blue channel densities.

 

This is an interesting observation. I have done many step wedge tests

comparing PMK, Rollo Pyro and Pyrocat-HD. Rollo Pyro at the 2:4:100

dilution and Pyrocat-HD at 2:2:100, when developed for the same time and

temperature, have almost identical printing densities with alternative

processes requiring UV radiation. However, the Rollo Pyro negative will

read about log .15 more than the Pyrocat negative when read through the

blue channel. It is important to understand that the blue channel does not

give you a very accurate idea of printing contrast for UV processes,

either with Rollo Pyro or with Pyrocat-HD. In fact, if you test step

wedges made with either of these develoeprs against a Stouffer you will

find that at the higher densities you will get almost two full stops, or a

lot increase of about 0.60, with the staining negatives.

 

>

> In printing both step wedges and negatives on various papers, azo,

> platinum, variable contrast, I attribute any difference in results to

> this difference in maximum UV/Blue density between pyro and

> catechol/pyrocatechin negatives, not to any particular difference in

> the type/color stain of the two.

 

The brownish/yellow color of pyrocatechin provides more actinic filtration

than the greenish/yellow stain of pyrogallol, at least when comparing

Pyrocat to either PMK or Rollo Pyro. In fact, the green stain of PMK and

Rollo Pyro does not come from pyrogallol but from metaborate. Pyrogallol

developers that use sodium carbonate (Kodak D-1, Wimberley WD2D) actually

have a stain that more closely ressembles Pyrocat than either PMK or Rollo

Pyro.

 

 

> I now have several questions for members of this forum:

>

> Has any one achieved higher differences between visual and UV/Blue

> channel densities with catechol/pyrocatechin, and if so using what

> developer/technique?

 

I believe that was addressed above. My blue channel readings are lower

with Pyrocat than with Rollo Pyro/A, though the difference is only about

log 0.15. And, as noted earlier, the actual printing density of Pyrocat is

higher than Rollo Pyro because the brown stain offers more actinic

filtration than the green stain of Rollo Pyro. Again, the key here is that

the blue channel of a color densitomer does not show actual printing

density with a UV process.

 

 

> Is the tanning effect of catechol/pyrocatechin greater than pyro, and

> does this limit the stain of catechol/pyrocatechin versus pyro? Is

> there a method to limit the tanning effect?

 

Am not sure about this. But why would you want to limit tanning? My

understanding is that tanning is one of the reasons for the high defnition

of this type of staining developer.

 

Finally, let me remark that pyrocatechin has one outstanding advantage

over pyrogallol, and that is the fact that it is much less likely to

develop uneven staining.

 

Hope these comments are of some use to you.

 

Sandy King

I have experienced generally lower fog levels with Pyrocat-HD than with PMK and other pyro developers, so I wonder if Sandy is correct that you may have added too much phenidone, which can produce high fog levels of not properly restrained.

 

I measured density on a PMK neg and a pyrocat-hd neg that were taken on the same day. D-max on the PMK was 1.38, and the blue channel read 1.71. The pyrocat-hd neg read 1.31, and the blue channel was 1.48. So it appears that the PMK neg picks up about two stops from stain, whereas the Pyrocat-HD neg only picks up 2/3 stop. However, reading the blue channel doesn't necessarily tell us how much UV light is restrained by the stain, and it is UV that most alternative processes require for printing. One of the reasons alt process folks like Pyrocat-HD is it gives faster printing times while still retaining the overall benefits of a staining developer. Also, it costs about half what PMK costs per liter of working solution.

The fog occurred with fast films, HP5+, not wiht FP4+, I mix my developers fresh at time of use, but I do use stock solutions of phenidone in methyl alcohol, and I wonder if this may have contributed to the fog? If I get a chance I may retest Pyrocat-HD with phenidone that was not in a stock solution. I tested both pyro developed negatives and catechol developed negatives with a colorimeter, and they had essentially the same spectral absorption, which led me to concluded that printing difference was probably due to differences in maximum stain density rather than a qualitative difference in stain color between the two developers.

I don't actually think that the alcohol in the phenidone solution would cause the high fog. In fact, I actually mix my phenidone in alcohol before adding it to the stock solution because it is so difficult to dissolve in water alone. However, how did you determine the proper amount of phenidone to add based on phenidone in alcohol solution. Phenidone has extraoridnary regenerative qualities so doubling the amount, even though miniscule, would I think have a really important afffect on shadow density.

 

The other issue of course is the type of film. Both HP5+ and BPF are old type emulsions that have really thick gelatin layers and you must take great care to not over-develop these films when using any of the staining developers. If you do develop too long you will get a real high fog built-up very quickly. I know a number of alternative workers who quit using staining developers with these films altogether becaue of the high general stain which causes real length exposure times. Even so, most alternative workers who have switched to Pyrocat-HD have reported that they get lower general stain with Pyrocat with these films than with PMK and Rollo Pyro.

 

Regarding your absorption test, based on your analysis I suspect that your conclusion about the density of the stain is probably correct for VD and graded photograhic papers. However, what about processes that depend primarily on UV radiation in the 340-400 nanomeeter rnage. Did the colorimeter you used for the analyis of the spectral absorption have the ability to read UVA and UVB radiation? My color densitometer, an X-Rite 811, is not capable of reading this low and consequently can not give me an accurate idea of the actual printing densities with processes such as carbon and pt/pd with stained negative

I use an Ohaus scale to measure my phenidone, checked against standard weights, seems accurate. When I use Rollo Pyro with HP5+ I rarely get fb+fog levels above .15 unless the film is old or has had too many long airplane trips; however, I mix Rollo Pyro as I use it, always fresh, I find if I use older stock solution increased fog, and streaking occur. I found higher levels of fog with Pyrocat-HD on HP5+, but given the comments that it develops with low fog, I suspect some variable in my technique. I do remember reading the KBr is not a great restrainer for Phenidone, did you ever try Bensotriazole? I did not measure UV transmission; I am in search of a UV transmission spectrometer. I think that measuring transmission/absorption spectrum of the stain removes density as a variable and will provide the best data on differences in stain between the two developers.