mac asks:
A while back, there was a discussion of clearing gum
Dichromate prints in which Judy suggested that a long soak
seems to be just as effective as clearing with potassium
metabisulfite. Being somewhat superstitious about these
matters, I always use the clearing bath even if they "look"
clear (i.e. no dichromate stain). Am I wasting my time (or at
least my chemicals)? Perhaps you chemists out there could
fill me in on how to tell whether my prints are clear.
I am no chemist but have been working with dichromated colloid pigment
processes for the past twenty five years Apart from pott metabisulfite, I
have used pot alum 5% sol which is a bit slow working ,I then went onto using
a 3%sol of Ilford acid hardener which is very fast acting.I to have shunned
the use of an extended wash for different reasons, most of my work is
three and four colour separation print making, I also do what I call
polycolour applications when I employ numerous colours,I just do not have
the time for lengthy time consuming soaks also another consideration in
England the water quality which,can be described as like the curates egg
good and bad in parts.
All the dichromate stain removers so far described are more accurately
seen as diminishers, the stain in fact is never removed from the shadow to
mid tone regions it is only lightened and the colour changed to a sensitive
blue/green /grey this slight colour is of no consequence in monochrome
print making ,but can prove quite a pain in three and four colour printing
as the slight stain keeps giving an erroneous cyan/green shift to the
colour balance,which is difficult to remove.
However about ten years ago I found the answer a 1%sol of sulphuric acid
did the trick .this bath changed the blue/green/grey to a very light grey
which was neutral in colour, bingo problem solved.I can see that there
could be archival problems with the classical processes employing paper but
the bath is very dilute and probably a hypo eliminator may solve this
problem,I have no problems of this nature as I use a laminated
polypropalyne substrate which is impervious to all chemical attack or so
the manufacture states!!{ I have a enough grey hairs to wonder}.I hope this
may be of some value.
By the way I made another Bobo in the last e:mail sent { Cliche Verre}
no signature ! sorry pete