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Processing
for permanence
Introduction:
Photography can be so familiar to us that we rarely stop to think about
the relevance of the permanence of our images. While some photographers
may argue that there is little need to take care with the processing
of Black and White photographs there is also an argument that photographers
have a special responsibility to make sure their pictures are as stable
as the means permits. One reason for this is that we can make images
to be passed down through many generations but there is also another
one that relates to the environment. As artists, do we have a responsibility
to use the earth's resources as effectively as we can?
Generally,
processing for permanence does not require any different methods or
additional steps in the process other than those normally used; CAREFUL,
SYSTEMATIC WORK IS THE KEYNOTE. One aspect of making prints for permanence
is the use of Fibre based paper.
STABILIZED
PRINTS: In some kinds of photographic work (like newspapers ) the
stability of prints is not important: they are discarded immediately
after use. These prints are referred to as STABLE PRINTS. This
means the silver halide is converted to compounds that are only temporarily
stable. This process means that the photographer pays little attention
to times, temperatures, the condition of chemicals and the methods;
only a short stop, fix and wash time are used as there is often some
urgency to just get an image. Negatives on the other hand should ALWAYS be fixed and washed properly.
PERMANENT
PRINTS: These prints are processed to a level that will allow them
to survive for about a life-time without showing signs of age. Generally
this process involves following the manufacturers basic specifications.
Fixing for the correct time in a fresh solution of fixer followed by
the recommended washing time.
OPTIMUM
STABILITY : Photographs intended for long term keeping should be
processed for optimum stability. These prints are refereed to as ARCHIVAL
PRINTS. This should not be taken to imply that they can not be harmed,
but that they have been processed for optimum permanence. This is the
process that is used to make "Fine Art Prints".
CAUSES
OF PRINT DETERIORATION : Apart for inappropriate storage and handling
, there are two main causes of print ageing that relate to processing.
The first is insufficient fixing and the second is insufficient washing.
FIXING:
The purpose of the fixer is to dissolve all the undeveloped light sensitive
halides left on the emulsion that were not turned to metallic silver.
During the process, by-products of this reaction form in the fixer as
complex silver compounds. As more prints are fixed in the bath, the
saturation of these silver compounds becomes greater and when the concentration
reaches a certain critical level, some relatively insoluble silver compounds
are formed. The stability of prints and negatives, is impaired by traces
of these complex silver compounds (products of the fixing reaction)
and can remain in the material due to a shortened fixing time or an
excess of silver compounds in the fixer, a condition that exists when
a fixing bath has been used beyond its useful capacity. THESE COMPOUNDS
CANNOT BE REMOVED BY WASHING! As the concentration of silver in
the fixer increases, so does the time required for complete fixing of
the print. This means that you should test your fixer frequently to
make sure that they have not reached a critical level of these compounds.
CORRECT
FIXING: There are many different ideas and methods about correctly
fixing prints. As we have seen earlier, whatever method is used it is
essential that ALL the undeveloped silver halides in the emulsion must
be dissolved by the fixer so that the silver compounds formed in the
process can be removed from the material by washing.
AGITATION:
As in development, one of the most common fault in fixing is often not
the fixer itself, but making sure that fresh chemical can reach ALL
parts of the print. It is not enough to throw a print or a whole heap
of prints in the fixer and wait for the suggested time. The fixer can
only do its job if it reaches all parts of the print for the required
time, and fresh chemical is moved across the surface during the processing
time. The effect of poor agitation is seen as a stained patch in the
centre or edge of the print where the chemical did not reach.
SINGLE
BATH FIXING
Prints
can be fixed successfully using a single bath but you must be very careful
with your methods. I use this method when I have limited sink space
to work in. In this case it is wise to use a stop bath as this prevents
the carry over of developer (which is an alkaline) into the fixer. The
stop bath should be mixed as follows:
KODAK
STOP BATH SB 1
Water....................................
1.0 litre
28%
Acetic Acid........................... 48ml
(28%
acetic acid is made from 3 parts of glacial acid with 8 parts of water.)
It
is important to remember that Glacial Acetic Acid freezes at a much
higher temperature than water (12 degrees) and should be stored in a
diluted form.
As
successive sheets of photographic paper are placed into the fixer, the
quantity of silver in the fixer builds up. The recommended number of
8x10 prints per gallon of fixer is about thirty, although this will
vary according to the density of the prints.
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