Jeffrey D. Mathias (jeffrey.d.mathias@worldnet.att.net)
Fri, 29 Oct 1999 00:41:04 -0400
As with most scientific studies, the end never comes.
A point has arrived at which data can be disclosed and review and
further study sought.
This latest study involves the composition of Ferric Oxalate powder used
as the sensitizer for the Pt/Pd process. This work may be found in my
Guide at the following link.
This work continues from the previously reported studies (in the Guide):
Comparisons of Ferric Oxalate Powders
Oxalic Acid Concentration in the FO Sensitizer
Threshold for FO Solutions (was DOP solutions)
*** Verification of FO Powder Composition ***
http://home.att.net/~jeffrey.d.mathias/guide/FO_composition.htm
This study determines the content of ferric oxalate in a FO powder by
measuring the specific gravity and using Dick Stevens' relationship of %
FO concentration and Specific gravity to determine the FO
concentration. The study also investigates the influence of Oxalic Acid
and EDTA on the measurement of FO concentration
The measurements of this study show the composition of the Vizcay FO
powder (a preparation procedure for this FO powder is explained in
detail in the Guide, from link at bottom of post) to be 95% ferric
oxalate by weight (this had previously been estimated at 98%). Further
measurements are currently being made on FO powder from B&S and
Artcraft, and will be reported when complete.
This study also demonstrates the usefulness and ability of the Stevens'
relationship.
As this study investigates the amount of ferric oxalate available, a
further study may investigate if all or how much of the ferric oxalate
is active. More is being investigated on this with John Melanson and
perhaps others.
This work should provide a better understanding of the formulas for the
sensitizer solution and resulting coating solution. It must be
remembered that it is not necessary to mix an accurate coating solution,
but it is critical to make a solution stronger than the threshold to
avoid unnecessary weakness in the print. (The thresholds are determined
by actual prints.) Just as it is necessary to restrict the coating to a
defined area and not spread it too thin.
Other sections have been added to the Guide in Chapter 6.
Formulas for FO Sensitizer Solutions
and a
FO Sensitizer Formula Calculator (requires a JavaScript capable browser)
http://home.att.net/~jeffrey.d.mathias/guidep/formulae_calculator_FO.htm
This calculator and the Metal Solution Calculator will provide the
solution formulas for the various parameters of materials used,
sensitizer solution strength, volume required, based on the empirical
verification of process equation relationships (one metal for one
sensitizer).
-- Jeffrey D. Mathias http://home.att.net/~jeffrey.d.mathias/
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