[pure-silver] Re: Polycontrast Paper Performance / Cold lite

  • From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
  • To: <pure-silver@xxxxxxxxxxxxx>
  • Date: Mon, 18 Oct 2004 17:26:57 -0700

----- Original Message ----- 
From: "DarkroomMagic" <info@xxxxxxxxxxxxxxxx>
To: "PureSilverNew" <pure-silver@xxxxxxxxxxxxx>
Sent: Monday, October 18, 2004 2:57 PM
Subject: [pure-silver] Re: Polycontrast Paper Performance / 
Cold lite


> RC papers need to be developed-out. Pulling them 
> prematurely results in weak
> blacks and uneven development. FB papers, on the other 
> hand, can be
> developed from 2 to 6 or 8 minutes with slightly 
> increasing contrast.
>
> Factorial development is not covered in my book (yet), but 
> it is covered
> briefly in AA's 'The Print'. Basically, you measure the 
> time until you see
> the mid-tones developing. Then, multiply that time by a 
> factor of 4 - 8 (I
> use '6') to get the total development time. Apply this 
> consequently, and you
> can make up for temperature and developer exhaustion 
> changes, always getting
> consistent contrast. It's a proven method that only works 
> for FB papers.
>
>
>
>
>
> Regards
>
>
>
> Ralph W. Lambrecht
>
>
   I think the distinction should be between developer 
incorporated paper and regular paper. These days most, but 
not all, RC paper has an incorporated developer so that it 
can be used in rapid access "activation" processors. No 
current fiber paper has the developer because they are never 
used in these processors. The incorporated developer makes 
the image come up fast and develop completely in a 
relatively short time. There is little variation in the 
image possible by variation of either development time or 
developer formula.
   Fiber paper and non-developer-incorporated papers respond 
to some extent to variation in exposure and development. In 
fact, despite the conventional wisdom, development time 
_can_ be used to compensate somewhat for exposure. Both 
kinds of papers need to be fully developed if they are to 
have good blacks. There is little variation in contrast from 
variation of development. Again, the curves are parallel to 
each other, they move along the exposure axis but not in 
slope.
   The emulsion of RC paper is not fundamentally different 
from that on fiber paper. The differences are mostly in the 
substrate. Fiber paper is coated with one or more layers of 
hard gelatin containtaining the reflective agent; usually 
barium sulfate (baryta). The gelatin layer is essentially a 
sizing to prevent the emulsion from soaking into the paper. 
However, it also acts as the reflective surface, and in 
textured papers, can be calendared to form the texture.
   RC papers are coated on both sides with a plastic. The 
plastic also acts as a sizing but differs from the the 
gelatin coating in that the gelatin is permiable by water 
and the plastic is not. The plastic coating also holds the 
reflective material; usually Titanium dioxide in RC papers. 
The emulsion is coated on top of the plastic layer. Its 
possible that a substrate is used on RC paper, as on film, 
to improve the adhesion of the emulsion to the support. 
However, there is no fundamental difference in the emulsion 
itself.
   The development time required to achieve a reasonable 
approach to maximum black varies with the type of emulsion 
and the type of developer. Cold tone papers like Azo or the 
late, lamented Kodabromide, develop rather quickly, 
development being complete in about one minute in an active 
developer like Dektol. Warmer tone papers generally develop 
more slowly. For most enlarging papers which do not have 
incorporated developer about two minutes is recommended. One 
can find advise to use very long development times. A mentor 
of mine when I was in junior highschool said not to develop 
for less than 8 minutes! Well, the result was difficulty 
with fogging and, on the paper I used at the time (Gevaert 
Artex), noticable image spread.  I didn't wise up to this 
for some time. In any case, development time should probably 
not be extended beyond about four minutes. Generally, 
development time has to be extended somewhat as the 
developer is used. When it becomes excessive the developer 
should be discarded. Four minutes is about the limit.
   Some special formulas, like the Agfa Direct Brown Black 
developer require long development time but they also do not 
acheive the Dmax of more active developers.
   Most papers are capable of greater density than is usable 
in a reflection print. There has been a lot of nonsence 
written about paper Dmax, silver-rich papers, etc. In fact, 
nearly any paper will produce deeper blacks than can be seen 
by reflected light. Examinination of these images by 
transmitted light will often show detail in shadows or dark 
objects that appear completely black by normal reflected 
illumination. One can also have an impression of deep blacks 
due to the nature of the image. Shadows in a contrasty image 
will tend to look blacker than they are as will shadows or 
dark objects which are small compared to the brighter areas.
   Any surface scattering from a textured or matte surface 
will also limit both Dmax and contrast of a paper. The 
highest contrast and darkest blacks are on glossy RC or 
ferrotyped glossy fiber paper.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx 

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