New Silver Chloride Azo type paper

[Photo Engineer]

I have been able to perfect (well, as far as I can go anyhow) an Azo type paper that is green (ortho) sensitive. It looks like regular Azo the way I make it, but is at least a stop faster.

Now, this might be interesting with negatives processed in staining developers, but IDK. I'm putting this up here for a response.

What do you think?

PE

 

[rootberry]

Well, my first response is: Gimme!

being that it is a whole stop faster is also very nifty. There are a lot of folks who miss AZO, I know I am one of them.. I still have 30 sheets or so of grade 3 that I haven't been able to make myself use.

Anyways, I think it sounds great PE !

 

[Jerevan]

Sounds interesting to me. What ballpark exposure times do you get? Is it complicated to make?

 

[gbenaim]

I'd be very interested in it if you need some testing.

 

[Shawn Dougherty]

What do you think?
PE

Well, that's great news... but, are there plans to produce and market this emulsion or would this be a home brew alternative?

 

[removed account4]

Well, that's great news... but, are there plans to produce and market this emulsion or would this be a home brew alternative?

DITTO

 

[Andrew Moxom]

Could you ask Ilford to do a run of it

 

[Photo Engineer]

This is a trial baloon for something that has never been made before AFAIK. It can be made at just about original Azo speed in grade 2 or 1 - 2 stops faster in grade 3. I'm still working on this.

PE

 

[David A. Goldfarb]

Sounds great. A stop faster, green sensitive, should be usable as an enlarging paper, particularly with cold light (and even more particularly with the older greenish tubes).

How are the keeping qualities, if you've tested that yet?

 

[bdial]

I'm not a LF contact printer yet, but this is extremely cool.

 

[JLP]

Very interested too. Azo speed is fine but a stop faster don't hurt as long as the paper has the quality that you envisioned.
What it comes down to is cost within reason. Look forward as always to see where this goes.


jan

 

[Ole]

This seems very interesting indeed...

 

[jgjbowen]

I can't wait to see some prints or perhaps read a review by someone like Alex who has used Azo and your other papers.

Keep up the good work PE.

 

[Photo Engineer]

Well, here is the problem. If you use the green sensitized emulsion with regular negatives, you will probably see no difference at all. My question is regarding staining developers and their effect on green sensitive contact papers, of which there are none AFAIK.

So, if you don't use staining developers, this paper would probably be of no use whatsoever. Just an ordinary emulsion. After all, most enlarging papers today are green sensitive.

So that is the question here. How do blue sensitive emulsions vs ortho sensitive emulsions compare when printed with negatives developed in staining developers?

PE

 

[Ole]

That is indeed the question. But since most (all?) the green-sensitive papers available today are vari-contrast, the only thing we can be certain of is that printing stained negatives on VC paper leads to much reduced contrast compared to printing the same negative on a (fixed grade) blue-sensitive paper, all other factors being kept as equal as practicable.

 

[Christopher Nisperos]

My question is regarding staining developers and their effect on green sensitive contact papers, of which there are none AFAIK. . . . How do blue sensitive emulsions vs ortho sensitive emulsions compare when printed with negatives developed in staining developers?
PE

Hi Ron,

Judging from your question, I take it that you don't have any stained negatives. That being the case, why not just send some of this paper to one of us to test for you? I'm sure you'll have a sea of happy takers ... and obtain some valuable practical testing information in exchange!

Happy 2008,

Christopher

 

[Tom Hoskinson]

Ron, I am a (5x7 and 8x10) contact printer who still has a small stash of AZO. I would love to try your new emulsion/paper.

 

[jgjbowen]

Ron,

I use Pyrocat HD with my TMY negatives and develop them for contact printing on Canadian Grade 2 Azo. I also have Azo in old grade 2, grade 3 and some ancient grade 4. I also have some Haloid I could test against your paper. Let me know if I can be of assistance.

 

[Steve Sherman]

PE

 

[Steve Sherman]

PE

Keep us posted, very interested!

 

[Photo Engineer]

Ok, this might interest you but many graded enlarging papers today are ortho sensitive. This was a surprise to me too. The reason stained negatives give oddball contrast on VC papers is obvious, but the results on a graded paper are kinda unknown I guess.

If you wish to test your paper for green and blue sensitivity, expose them through a wratten 98, 99 and 70 and this will give you the relative speeds to B/G/R light. Of course Ilford MGIV would be your reference. You may be surprised to see the results. I was.

PE

 

[JBrunner]

PE,
You may be interested to know that one of the reasons I favor PMK is because of the effect the green stain seems to have when split contrast printing. The PMK negs seem to split the hard and soft exposures more effectivly than negatives developed by other means.

J

 

[Photo Engineer]

Well, I can't make a VC Azo yet, but I have ideas how. I have read about what you describe though. I'm referring though to many enlarging papers having green sensitivity even though they are not VC papers. This is probably one way they are picking up some speed.

PE

 

[Kirk Keyes]

PE - a green sensitive paper that is graded, i.e. not multicontrast, will respond just fine to a stained negative. The paper can not and will not react any differently from a plain old un-stained negative. Follow the link on this page on my web site and you will see a comparison of the stain on a couple films processed in two staining developers, one in PMK and the other in Pyrocat-HD. The films are TXT320 and FP4+, but I don't think there is a significant difference in that. The films were bleached and the silver was removed, leaving only the stain behind and then the films were scanned in a spectrophotometer.

There are two lines plotted for each film, one from a section of film base with only fog, and the other line is from a portion of the film with density - they were exposed with a Stouffer step wedge and Step 1 or 2 is used for these.

Keep in mind that the plots are only intended to give a general idea of the stain density - the areas of film used were not matched in density nor was the development of each film matched for gamma or CI. They just happened to be the sheets I grabbed to do the test with...

Anyway, you can see the Pyrocat really doesn't have much absorbance in the green or even the blue, especially when compared to the PMK neg. I think there will be minimal difference in exposure with a Pyrocat neg using your green-sensitive paper when compared to a blue-sensitive one, except it may be a bit quicker as it transmits a bit more light in the green. The PMK neg will probably print noticeably faster with the green sensitive paper as it has much less absorbance in the green so it should let more light through.

I think this is what you are trying to get at, right?

 

[Kirk Keyes]

http://keyesphoto.com/KDKtech - Spectral Scans of Pyro Developed Film.html

Forgot to add the link!