~~~~~~~~ Excerpt from the Guide to Platinum Palladium Photographic Printmaking by Jeffrey D. Mathias ~~~~~~~~
No part of this document may be reproduced in whole or in part without the express written permission of the Author.
updated December 2000

 
Testing the Ferric Oxalate
This test is comprised of three tests and two functions.  The accomplishment of both functions is critical to the passing of the Ferric Oxalate solution.  A solution should be made up containing only Ferric Oxalate without any additives so as to not introduce other possibilities.  Later actual sensitizer solutions can be tested to determine if any additives adversely affect the function of the Ferric Oxalate.
Note: Testing, as with any handling of Ferric Oxalate, should be carried out in safelight illumination.
In order to pass this test, the Ferric Oxalate solution must first NOT turn color.  This demonstrates a desired lack of ferrous material that may be present from contamination or exposure fogging.  Second, the solution must turn color to indicate the proper conversion to ferrous when called for.
To test the Ferric Oxalate solution:

PART I  -  TEST #1

  • Place some Ferric Oxalate solution into a shot glass.
  • Add a crystal of Potassium Ferricyanide (one or two crystals is plenty to do the job).
  • Nothing should happen.
  • TEST #1 FAILS if the solution darkens (do not consider any natural orange or red color from the Potassium Ferricyanide, the failure color is likely to be blue, gray, or indigo).  The solution likely contains Ferrous Oxalate.
  • If the solution (used in TEST #1, FAILED) is OLD SOLUTION, make a fresh solution from the stock powder and test again (TEST #2).
  • If TEST #2 FAILS and the stock powder is OLD POWDER (powder was probably not stored correctly or it may have gotten hot or exposed), make a new solution using new stock powder and test again (TEST #3).
  • If TEST #3 FAILS, then the new powder is defective and should be returned to the vender for replacement.
  • If TEST #3 PASSES, continue test PART II with the new solution from the new stock powder.
  • If TEST #2 FAILS and the stock powder is NEW POWDER, then the powder is defective and should be returned to the vender for replacement.
  • If TEST #2 PASSES, continue test PART II with the new solution.
  • If the solution (used in TEST #1, FAILED) is NEW SOLUTION, then the stock powder is defective.
  • If the defective stock powder is OLD POWDER, then it has probably been stored incorrectly.
  • If the defective stock powder is NEW POWDER, then the powder should be returned to the vender for replacement.
  • TEST #1 PASSES if nothing happens (no darkening or color), then continue with test, PART II using the tested solution.
    • PART II
  • Place shot glass with Solution in UV light.  It should turn deep indigo blue.
  • If the solution does not turn a deep indigo blue, then the Ferric Oxalate is bad.
  • If this is a NEW SOLUTION from a NEW POWDER, first try adding some more Potassium Ferricyanide. If there is still a failure to turn blue and the Potassium Ferricyanide is good, then the powder is not Ferric Oxalate. Return the powder to the vender for replacement. (If this happens again, find a new vender.)
  • If this is a NEW SOLUTION from an OLD POWDER (that has worked before), then somehow the solution was made incorrectly.  Make a new solution from the old power and re-test.
  • If this is an OLD SOLUTION from an OLD POWDER (that have both worked before), then the Potassium Ferricyanide must be bad. (This is unlikely , but there is no other reason.)
  • When the solution turns dark blue only under the UV light, then the TEST has PASSED and the Ferric Oxalate is OK to use in a sensitizer solution.


    • Table of Contents
     

    page visit counter