From: Richard Knoppow (dickburk@ix.netcom.com)
Date: 04/11/00-08:50:12 AM Z
At 11:41 PM 04/10/2000 -0700, you wrote:
>
>----- Original Message -----
>From: Richard Knoppow <dickburk@ix.netcom.com>
>To: <alt-photo-process-l@skyway.usask.ca>
>Sent: Monday, April 10, 2000 9:12 PM
>Subject: Re: Kodak Azo Paper Question
>
>
>--snipped--
>> Azo is a conventional chloride paper with nothing magic about it. I have
>> a number of old Kodak sample prints on Azo. It doesn't look different from
>> Velox, Kodak's photofinishing paper other than having a slightly more
>> neutral tone (Velox is quite blue-black).
>> it suspect the differences noted by those trying Azo today have more to
>> do with differences in technique than anything the paper is doing.
>> Also, chloride papers like Azo don't change contrast much with
>> development. They come up to full development (where the Dmax is reached)
>> and further development doesn't change them much. Development is complete
>> in Dektol 1:2 in just over a minute.
>> ----
>> Richard Knoppow
>> Los Angeles,Ca.
>> dickburk@ix.netcom.com
>>
>
>Azo has a far greater range within the tonal values interms of acutence,
>that I noticed with Amidol prints contacted on Oriental Seagull and then on
>Azo with Amidol paper developer for both papers.
>
>BTW it was mentioned to me by an old (70+ in age) pre press printer who
>remebers the original Azo Chemical Cibichrome ... "Hey, wait a minute!" I
>stopped him, but he didn't know any relationship between the Kodak B&W
>papers and that color paper; but something shook mymemory and I recall there
>may be a French term for the reduction of chemicals without disturbing the
>molicular properties of the chemistry. Is this pertenant to the finite
>properties of our Kodak Azo?
>
>Who can talk tothe Kodak tecs or call the Ciba Geiggi (spelling?) labs in
>Switzerland and get us adefinitive answer. Plot curves won't show the
>acutence.
>
>Steve Shapiro
>
>
>
The curves for Azo indicate its not any different than other papers as do
the samples I stil have of it. Its very good paper but not magic.
I think the old time pre-press guy was confounding two things, Azo paper
and Azo dyes. Cibachrome, not called Ilfochrome, is based on the work of
Dr. Bela Gaspar in developing the dye-destruction color process, also known
as Gasparcolor. The principle is that the dyes which are to form the final
image are in existence at the begining and are decolorized by the reaction
products of developing the silver image. The silver image is then removed
leaving a postive color image. Azo dyes are used in this process. Azo dyes
tend also to be more stable than the types of dyes produced in chromogenic
color film.
The confusion of Azo paper with Azo dyes is, I think, the source of the
idea that Azo paper has some relationship to Cibachrome, or is in any way
not a conventional paper.
The trade-name "Azo" was obtained by Kodak from one of the many companies
it acquired around the turn of the last century. I believe the name Azo
means somthing like A to Z - O suggesting its good for all purposes.
Its very unlikely the Azo emulsion of the 1930's or the current product
bear much resemblance to the original emulsion. I suspect Kodak changed it
many times.
Amidol has the reputation of producing very deep blacks. I think from my
experience with it that the actual Dmax is no higher than for other
developers but Amidol tends to a very neutral or bluish black which give
the impression of being very deep. Someone with a reflection densitometer
would have to test this to substantiate it.
The fact is that many, if not most, B&W printing papers are capable of
densities which are beyond being useful. An examination of a good print
with deep blacks made from a negative with good shadow detail by
_transmitted_ light will often show that there is gradation in the shadows
which is not visible in ordinary illumination. In fact, its possible to
make a reflection print look nearly like a rear-illuminated transparency
but printing it dark and contrasty and illuminating it with very bright
light in a light box. The effect can be quite impressive. The point being
that even if a certain kind of paper _is_ capable of extraordinary maximum
density if may be of no consequence in making a print to be viewed in the
ordinary way.
To compare Azo against an enlarging paper fairly I suggest using an
enlarging paper of similar characterists, namely single-weight, glossy,
with no optical brighteners in the support or emulsion. Kodabromide
suggests itself. Also, the published curves for Kodabromide are similar to
Azo. The publlished contrast ranges are very similar for each grade. Since
both are neutral tone papers the use of Amidol on each should give similar
results as far as image color is concerned.
---- Richard Knoppow Los Angeles,Ca. dickburk@ix.netcom.com
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