Jeffrey D. Mathias (jeffrey.d.mathias@worldnet.att.net)
Thu, 29 Jul 1999 22:59:40 -0400
Melvin Dorin wrote:
> ... recommend another clearing agent, please let me
> know. Appreciate comments on personal experience.
No mater what clearing agent(s) one uses, they should run a test similar
to the one outlined in my guide. It's short enough and important enough
that I'll include it below (please excuse the formating or lack
thereof).
Clearing times may be ascertained by this test. It is recommended that
this test be
performed every time a new paper or coating chemistry is to be tried.
Also use this test
before a new type of clearing bath is used.
Note: Safelight illumination must be used for all coating and processing
during this test.
Only turn on other lights after paper is in wash water.
Coat the paper with a very definite edge to the coating. But do not let
the
coating mixture build up or puddle on this edge. (Removable tape is
handy
for this.)
Dry carefully so as not to push the mixture into a puddle at the edge.
Note: Puddling may cause a density at the edge of the puddle that
clearing will not remove.
Mark the edge with a dotted pencil line(s).
Without any exposure, process the paper.
Dry (hair dryer with heat may use used)
Evaluation is made under white light.
Note: Direct sunlight is to intense to evaluate. Shaded sunlight is OK.
Look very closely along the pencil line(s) for any differences.
Note: Insufficient clearing will be seen as yellowish or grayish
density in the coated area.
If there is no difference between the coated and uncoated areas,
then clearing was successful. Even the slightest difference will
indicate incomplete clearing.
It is best to determine and use the least amount of time necessary to
clear a paper.
However do remember that if the strength of the clearing agent is
increased too high,
then the paper will be adversely affected. Also note that higher
strengths of acids will
require higher safety precautions. It is also believed that a weaker
acid bath will more
efficiently clear the print.
-- Jeffrey D. Mathias http://home.att.net/~jeffrey.d.mathias/
This archive was generated by hypermail 2.0b3 on Thu Oct 28 1999 - 21:40:38