AZO (like) paper from Michael And Paula Chamlee

Ron,

What exactly does this mean in terms of the curve shape? Is there a difference in curve between a pure silver chloride emulsion and AZO?

And, why is it that all silver curves, VC and graded silver papers including AZO, appear to have very pronounced toes and shoulders, unlike the dichromated colloid processes which are for all practical purposes completely linear or straight line?

Sandy

Photo Engineer said:

I did indeed say that. It is a guesstimate on my part until I get enough hard data, but it looks to be true.

And, BTW, it is a common misconception that Azo is a pure AgCl emulsion. It has extended blue sensitivity, easily seen using a spectrosensitometer, which is not possible from a pure AgCl, so we have to wait and see how this paper looks with a battery of tests to 'compare' with Azo. I'm not implying that differences will be bad in any way though.

PE

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Sandy, I have been able to duplicate the Azo curve with a pure chloride emulsion, but not the spectral sensitivity nor the reciprocity failure, so there is something different in Azo regarding at least several factors that I can test for.

Again, this is neither good nor bad. If it works, it works!

As far as curve shape goes, I have no idea how the toe and shoulder of conventinal analog relates to alternative processes. I have seen all varieties of curves from analog conventional as well. I think it is a matter of what seems to please the customer, as the curves are derived by testing pictures on panels of observers.

It is possible to get many curve shapes from AgCl and AgBr emulsions, as it is also possible to get a variety of tones from green through blue and black to brown. I have done this just by varying addenda or dopants in the emulsion precipitation or the method of addition. For example, copper can produce a pronounced brown or sepia tone to silver halide images along with either a softer or sharper toe depending on method of addition.

You might find that dichromated gel and other processes have no toe or shoulder just due to the nature of the chemical reaction or due to the reaction with a particular gelatin. I have seen hints in the literature that suggest that for example, 250 bloom gelatin vs 75 bloom gelatin can alter curve shape of tanning based processes quite a bit.

I'm still working on a number of these problems, but perhaps if we put our heads together, we might come up with something radically different and, dare I say, better?

Carbon is one example. I have had a lot of ideas after working with your 'glop'. FWIW, to the readership out there, I by no means am denigrating Sandy's carbon materals, just giving his 'glop' a name. ~kudos Sandy for a wonderful 'product'~. I would guess that we might come up with something better that might make coating easier for the average bear. I would welcome a chance to work side-by-side with you Sandy to see if this is possible.

Warmest regards.

PE

Ron,

What I observe in my own work and testing is that all of the processes have curves rather unique to the process, but we can also move them around a bit with contrast controls. However, there is a special character to most of the processes that hangs in there even with contrast manipulation. In other words, no matter what we do it is virtually impossible to make a palladium curve look like a carbon curve. Yes, I know how to massage carbon to give it some toe and shoulder, but to do so puts me on the far fringe of normal printing.

I notice that your workshop on emulsion making and coating at the Formulary is right after my workshop on alternative processes (and that of Les McLean on B&W printing). If you are interested I may try to hang around a couple of days after the end of my workshop to discuss carbon coating. Or perhaps you could arrive a day or so early and watch some of the carbon work? I do agree that with out different knowledge bases we could probably come up with a better or simpler way of coating.

Best,

Sandy

Photo Engineer said:

Sandy, I have been able to duplicate the Azo curve with a pure chloride emulsion, but not the spectral sensitivity nor the reciprocity failure, so there is something different in Azo regarding at least several factors that I can test for.

Again, this is neither good nor bad. If it works, it works!

As far as curve shape goes, I have no idea how the toe and shoulder of conventinal analog relates to alternative processes. I have seen all varieties of curves from analog conventional as well. I think it is a matter of what seems to please the customer, as the curves are derived by testing pictures on panels of observers.

It is possible to get many curve shapes from AgCl and AgBr emulsions, as it is also possible to get a variety of tones from green through blue and black to brown. I have done this just by varying addenda or dopants in the emulsion precipitation or the method of addition. For example, copper can produce a pronounced brown or sepia tone to silver halide images along with either a softer or sharper toe depending on method of addition.

You might find that dichromated gel and other processes have no toe or shoulder just due to the nature of the chemical reaction or due to the reaction with a particular gelatin. I have seen hints in the literature that suggest that for example, 250 bloom gelatin vs 75 bloom gelatin can alter curve shape of tanning based processes quite a bit.

I'm still working on a number of these problems, but perhaps if we put our heads together, we might come up with something radically different and, dare I say, better?

Carbon is one example. I have had a lot of ideas after working with your 'glop'. FWIW, to the readership out there, I by no means am denigrating Sandy's carbon materals, just giving his 'glop' a name. ~kudos Sandy for a wonderful 'product'~. I would guess that we might come up with something better that might make coating easier for the average bear. I would welcome a chance to work side-by-side with you Sandy to see if this is possible.

Warmest regards.

PE

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Azo, a silver chloride paper, has the best keeping properties of any paper I know of. Last month Paula successfully printed on Azo that was over 75 years old.

The new paper we tested looked exactly like "old" Azo. We printed a negative on "old" Azo, and then a few minutes later, in the same tray, printed the same negative on the new paper. The prints were virtually identical.

Hi Michael - Can you tell us in which country the new paper will be made? I am hoping it will be China. The Chinese have a great record of keeping low-tech processes such as vacuum tube manufacture, die casting, injection molding and of course, paper coating, alive and well.

Best of luck... order to follow!

Jon

Michael A. Smith said:

Azo, a silver chloride paper, has the best keeping properties of any paper I know of. Last month Paula successfully printed on Azo that was over 75 years old.

The new paper we tested looked exactly like "old" Azo. We printed a negative on "old" Azo, and then a few minutes later, in the same tray, printed the same negative on the new paper. The prints were virtually identical.

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Photo Engineer said:

I did indeed say that. It is a guesstimate on my part ... PE

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Sounds like a post to a thread I started a several weeks ago.
IIRC, it was on a technicality that most if not all print papers
have DI emulsions. Something to do with speed and/or
contrast. S. Anchell mentions adding a little when
coating at home in order to vary the contrast.

I did follow up with a check at Freestyle. They had
assured me about three years ago that NONE of their
graded paper emulsions contained developer. Since then
they've come out with their EDU line. The Ultra does have
a DI emulsion and is quicker to develop in a Developer.
Another paper has a DI supercoat.

I did a quick check of some other papers and found none
suitable for activation processing. I still believe that the
claim, most if not all papers have DI emulsions, is based
on a technicality.

The test is very simple; expose, then immerse in a
carbonated solution. I'd consider any more than a very
light gray a source of trouble. My check may have
been for graded RC papers only. Dan

Dan, I have checked a host of B&W papers for keeping and incorporated developers. I find that they vary in level from zero to a lot. The Kodak Polycontrast IV seems to be the highest and the Ilford MG IV seems to be at a middle level.

I have not checked Azo personally, but prior knowledge tells me that it had none and has always had superb keeping. It does contain other addenda though as evidenced by the different contrast grades and the wedge spectrograms compared to a pure AgCl emulsion.

FWIW, Lupex was the Agfa version of Azo paper. It was also not a pure AgCl emulsion. I don't know how well it kept or what its properties were. I have never used it nor even seen prints (AFAIK) that were made on the paper.

Also FWIW, just having a pure AgCl emulsion does not assure good keeping or any Azo like property. Emulsions are all subject to radiation and heat 'death' and so something must be done to prevent this. It usually takes the form of addenda and dopants. I have mentioned that antifoggants and metal salts can be used. This includes benzotriazoles, phenyl mercapto tetrazoles, cadmium, copper, mercury and a host of other things.

None of the above has any meaning WRT the efforts by M&P though. If the company they use for R&D and production are savvy enough, they will come through for us all and M&P will get the kudos they deserve!

Sandy, I will be arriving early and that should give us some time to work in the lab together. I think that we might find some interesting common ground from which we might be able to leap off into the unknown and come up with some new and interesting things.

PE

[QUOTES=Photo Engineer]
"Dan, I have checked a host of B&W papers for keeping
and incorporated developers. I find that they vary in
level from zero to a lot. The Kodak Polycontrast IV
seems to be the highest and the Ilford MG IV
seems to be at a middle level."

I think this whole matter of DI emulsions should receive
much more attention. I did test by Expose and Carbonate
that one Freestyle paper I mentioned. Apart from quick
and dirty class room demonstrations and agitation drills
we do not need developer incorporated emulsions
clouding results from our picks of off the shelf
or Home-brew developers.

Bottom line; does it show. Perhaps a table should be
brought into being and it be made part of the APUG
data base. We each test and contribute. The test
should be standardized.


"FWIW, Lupex was the Agfa version of Azo paper."

Lupex was, Azo was. But Forte contact speed RC still is.
At least according to their Web Site. Dan

Dan, my point was that Lupex was not an AgCl emulsion. It was an AgCl/I emulsion with about 0.3% iodide.

Another point about chloride emulsions is the difficulty in chemically sensitzing them without causing severe keeping problems. Another problem is giving them blue speed without causing contrast loss. Etc.....

So, the bottom line is that what is often said about Azo is mostly hearsay and not fact as far as the actual formulation goes. It is closer to Lupex than one might imagine due to the fact that there are limited ways of achieving some goals. I would assume that Forte contact speed may be close as well, however for technical reasons anything coated on RC would have a different formula than something coated on Baryta. The environment on Baryta is vastly different than that of RC.

PE

Photo Engineer said:

And, BTW, it is a common misconception that Azo is a pure AgCl emulsion. It has extended blue sensitivity, easily seen using a spectrosensitometer, which is not possible from a pure AgCl, PE

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I tried a paper from Bergger that was quite a nice contact paper - it was, I believe a Silver Chloride/Iodide paper - Prestige Art Contact 2

So if AZO isn't a pure silver chloride paper - what exactly is it?

tim said:

I tried a paper from Bergger that was quite a nice contact paper - it was, I believe a Silver Chloride/Iodide paper - Prestige Art Contact 2

So if AZO isn't a pure silver chloride paper - what exactly is it?

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Tim, there is no simple answer.

If it is like Lupex and the Presitge it is AgCl/I. It looks like it is actually an AgCl/Br with a blue sensitzing dye and it contains a heavy metal salt to assist in reciprocity failure control. That would probably be Iridium or Rhodium (as chloride salts). Depending on speed and grain size, it is also probably sulfur sensitized.

In addition, it contains something for keeping, probably PMT and / or TAI. Along with all of that, it contains the ingredients that control contrast for all of the grades manufactured and for image tone. This includes a host of organic salts and copper (cupric nitrate or chloride) among other things.

The basic formula is similar to the AgCl that I posted previously but that formula is posted without the metal salts, iodide, chemical sensitization and washing steps. That formula does not have the blue sensitivity of genuine Azo, it has poorer reciprocity failure, but has the same speed and curve shape. It is about a grade 2 paper and requires about 2x the level of silver of genuine Azo to get the correct contrast. Diluting that emulsion 1:1 will lower silver 50% and the contrast by one grade. Adding addenda as I describe here will raise contrast to grade 2 and 3, but will not match Azo for LIRF, HIRF or keeping. Spectral sensitivity across the grades will vary. There are ways to keep LIRF, HIRF, and spectral sensitivity constant across the grades. This requires additional alteration of the formula(s).

The reason for this long answer is that each grade of Azo, and each 'version' of Azo made over the years was different, and so there is no one answer to your question. It starts as an AgCl, and then through addition of many other things such as Iodide, Bromide, heavy metal salts and organics, it becomes something different entirely for each contrast grade.

Just one more example, the older formulas for many paper products contained Mercury salts and Cadmium salts, but they were taken out of Azo and similar products in the 60s. This was a time when most all Kodak paper products underwent total redesign. So, there is 'old' Azo and 'modern' Azo. There is also the last batch of Azo which didn't come out right. Interestingly enough, it passed the Kodak release test, but fails in the hands of many users to meet the contrast specifications. This tells me a lot about what error was made by Kodak and what the users are experiencing.

Since Azo is release tested with a given exposure speed, but many users are using exceptionally long exposure times with low intensity light, I suspect that they are seeing LIRF which is manifest as a change in contrast as a function of exposure. I see the same thing in my 'Azo'. This is related to one of the heavy metal addenda, to a sensitzing dye, or to the sulfur sensitization step, or is a combination of effects from all three. So, the last Azo which performs differently is not really Azo even though it was certified by Kodak in their release testing.

PE

Photo Engineer said:

Since Azo is release tested with a given exposure speed, but many users are using exceptionally long exposure times with low intensity light, I suspect that they are seeing LIRF which is manifest as a change in contrast as a function of exposure.

Click to expand...

It also seems to change color as a function of exposure, especially with grade 3. Shorter exposures appear to be warmer.