From: Sandy King (sanking@CLEMSON.EDU)
Date: 12/09/02-10:09:57 AM Z
Cor,
First, about image color. I don't care about the native color of
either VDB or kallitype because all of the prints I make with these
two processes are gong to be toned. Prints made by any of the brown
silver processes, i.e. salted paper, albumen, kallitype and VDB, etc.
image should be toned because brown silver particles are much smaller
than the larger silver particles in modern silver bromide papers and
as such offer much more surface area to the elements. The primary
purpose of toning is to plate the silver with a more noble metal.
OK, it happens that toning also changes the color of both VDB and
kallitype. The citric acid formula that I use causes a similar color
change with both VDB and kallitype. Gold toner gives a
blackish/purple blue image, very attractive, platinum a more neutral
black look, palladium a black brown look, and a combination of
platinum and palladium something between neutral black and brownish
black. Some people have used dilute Rapid Selenium toners with VDB
and kallitype but I have experienced serious staining problems with
selenium and don't recommend it.
But to your main question.
I prefer kallitype for several reasons.
1. You can get darker shadows, i.e. more Dmax, with kallitype. With
kallitype the Dmax is equal to what you get with pt/pd, i.e. about
maximum of 1.47 with my papers and densitometer. With VDB the reading
is lower, with a maximum of about 1.39. This is not a great
difference but if you look at well-made comparison prints side by
side you will see more richness in the shadows with the kallitype.
BTW, this fact is often mentioned in the historical literature. Not
that the historical literature is always right but in this case the
literature agrees with my own observations and experience.
2. I can get greater contrast control with kallitype. With kallitype
contrast control is obtained by adding a few milliliters of a 4%
potassium dichromate solution to the developer. With no dichromate
added the exposure scale is about 2.4, two milliliters of the
dichromate solution reduces the ES to about 2.0, four milliliters
reduces it to about 1.8, and so on.
I have found that with VDB the addition of potassium dichromate,
either to the developing water or directly to the sensitizing
solution, is not effective as a contrast control agent. With VDB the
dichromate reduces sensitivity greatly but is quite ineffective in
changing the exposure scale.
The only effective way that I have found to alter the ES with VDB was
to make two stock sensitizing solutions, one the classic VDB formula
with ferric ammonium citrate, and another made up of ferric citrate,
and to then combine these in varying proportions for the final
sensitizer. With this procedure I am able to reduce the ES of VDB to
about 1.6, but this leaves me still quite short of the control
available in kallitype.
3. Kallitype is a DOP process and this fact allows me to establish
exposure and ES equivalents for a given negative with carbon. With a
new negative I carry out initial testing for exposure time and
contrast with kallitype. For example, I know that an exposure for
kallitype of 400 units with the HID lamp is equivalent to 150 units
with carbon, since carbon is about 1.5 stops faster than kallitype at
the same contrast. And I have similar data on the relationship
between the amount of potassium dichromate added to the developer in
kallitype to the sensitizer strength with carbon. This means that
once I have made the best possible print in kallitype in terms of
exposure time, contrast, and the use of any necessary burning and
dodging I can go directly to a carbon print without the need for any
further testing. This saves a lot of time.
The fact that I am using kallitype to proof for carbon does not mean
that this process does not have merit on its own. In fact I find that
I actually prefer the look of kallitype with many images to carbon.
Hope this answers your question.
Sandy
>I have a question for Sandy King, which I hope will also interest the list.
>
>Sandy, I understand you mainly work with the Kallitype process, not so much
>with VDB. What are the differences (image wise (colour, contrast etc), not
>technical) between Kallitype and VDB in your opnion, and why do you prefer
>Kallitype?
>
>I did do some Kallitype printing, and VDB in the past. I did prefer
>Kallitype it's black/grey image tone over the choclate brown image of VDB.
>But lately I tried VDB according to Wynn White, on Ed Buffaloe site:
>http://unblinkingeye.com/Articles/Vandyke/vandyke.html ; using double
>coating and goldtonening before fix. I must say I was realy pleasently
>surprised with the obtained colour scheme (blackbrown shadows, greyish
>midtones, and a hint of purple in the highlights)
>
>Cor
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