Chemicals

Water Coating Chem.      Sensitizers      Sensitizer Additives      Metal salts      Salts      Contrast Agents Processing Chem.      Developers      Clearing Agents Other

Many chemicals are used with the platinum palladium process that may not be used with other photographic processes.  Any chemical should be appropriately stored, handled, and used.  Storage and handling recommendations for most of these chemicals can be found in Chapter 2, Hazard Ratings and Storage Recommendations.  Descriptions and notes for their use in the platinum palladium process may be found in this and other sections.

   NAME
       FUNCTION
                             DESCRIPTION & NOTES

      Tap Water
                 Making Clearing Baths and Washing.
                             If high in iron, clearing will be adversely affected; use bottled water.
                             It is recommended to filter the tap water to 0.5 micron.

      Distilled Water
                 Making all coating chemistry and developer; rinsing coating brush
                             From steam distillation or reverse osmosis deionization.
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-------------coating chemicals----

      Ferric Oxalate
                  Sensitizer (used with DOP, developing out process)
                              Powder should be kept refrigerated and protected from light.
                              Must make up working solution 24 hours in advance.  It should last several months.
                              Do not heat nor microwave this solution.  Heat may harm it.
                              Keep the working solution cool and dark; but it is not necessary to refrigerate.
                              Light, heat, or time will convert Ferric Oxalate into Ferrous Oxalate.
                              Solution is greenish when ferric and yellowish when ferrous.

     Ammonium Ferric Oxalate
                   Sensitizer (used with POP, printing out process)
                               Make up working solution 24 hours in advance.  It should last several months.
                               Keep the working solution cool; but it is not necessary to refrigerate.
                               Light, heat, or time may convert Ferric into Ferrous.

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      Oxalic Acid
                   Sensitizer additive
                               White crystals. Clumps with humidity.
                               Studies have found a strength of 3% to 5% to provide better print sharpness.
                                It dramatically helps clearing and reduces clearing times.

      EDTA
                   Sensitizer additive
                                White powder.
                                It dramatically helps clearing and reduces clearing times.

         Note:  More information on how individual sensitizers and additives effect the print
                    can be found in the section Preparing the Coating Solution.
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      Platinum [ K₂PtCl₄ ]
                    Metallic Salt
                                 Red powder or crystal.
                                 Any yellow or brown material is K₂PtCl₆, which is only slightly soluble in water.
                                 K₂PtCl₆ leaves a precipitate in the solution which may result as black specks.
                                 Do not heat the solution or the powder to greater than 140F.
                                 Heat can convert it to K₂PtCl₆ (especially over 140F).
                                 The existence of sodium increases the susceptibility of conversion into K₂PtCl₆.
                                 When in a hot climate, the substituting of potassium for sodium with the
                                      palladium salt  will help prevent black specks in the print thought to be
                                      caused by K₂PtCl₆.

      Palladium [ Li₂PdCl₄, Na₂PdCl₄, K₂PdCl₄ or PdCl₂ ]
                     Metallic Salt
                                  Brown crystal.
                                  The double salts (#₂PdCl₄) are Hydrophilic making weighing difficult.
                                  Less expensive than platinum.
                                  Has other advantages too; see mixing coating solution.
                                  To get the mixture into solution the first time, it must be heated.
                                       Use the double boiler method with hot water (very hot tap water will work).
                                       Once in solution it will stay there, except when potassium or supersaturated
                                       solutions are used, requiring heating before each use.
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      Lithium Chloride
                    Salt
                                  White crystal.
                                  This may be used in the palladium solution.
                                  When used with Ammonium Ferric Oxalate sensitizer, this salt produces
                                       the most neutral color.
                                  When mixed with water, heat is released (exothermic reaction).
                                  CAUTION: Solution can get  hot to the touch quickly when mixed and may
                                                      break a weak bottle.

      Sodium Chloride
                    Salt
                                  White crystal.
                                  Table salt works, but prefer use of the more expensive reagent grade.

      Potassium Chloride
                     Salt
                                  White crystal.
                                  This may be substituted for the NaCl in the palladium solution to keep Na
                                       away from the platinum salt. The disadvantage is that the required
                                       palladium solution will not stay soluble at room temperature. The
                                       solution must be kept warm during each use.

          Note:   More information on how individual metal salt solutions effect the print
                       can be found in the section Preparing the Coating Solution.
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      Potassium Chlorate
                    Contrast Agent
                                White crystal. Strongly reactive, see Safety section.
                                A little will prevent fog and controllably increase contrast.
                                The print seems to lose substance without some Potassium Chlorate.
                                Too much will degrade the paper or cause image graininess.
                                Increases exposure time.

      Hydrogen Peroxide
                    Contrast Agent
                                Clear liquid; typically a 3% solution.
                                Works like Potassium Chlorate, but will not hurt the paper.
                                May cause platinum salt to degrade (especially at higher concentrations).
                                Not as controllable due to its instability. Mixing fresh from stock helps.

      Ammonium Dichromate
                    Contrast Agent
                                White powder. Health hazard, see Safety section.
                                Supposedly provides true contrast control.

      Potassium Dichromate
                    Contrast Agent
                                 Orange powder. Health hazard, see Safety section.
                                 Provides contrast control internally (in coating) or externally (in enhancer.)
                                 May give some nice edge effects and sharpness.
                                 Edward Weston mentioned in his daybooks that this brought life to clouds.
                                 It is used up, the Potassium Oxalate Bath must be kept replenished if used
                                      externally.
                                 If used internally, some will collect in the enhancer (developer) thus altering it.

        Note:   More information on how individual contrast agents effect the print can be found
                     in the section Preparing the Coating Solution.
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----------------processing chemicals----

      Potassium Oxalate
                    Developer
                                   White crystal. Endothermic when mixed with water.
                                   This developer produces the best depth and substance in the print.
                                   To mix, the water should be hot. The reaction of going into solution is
                                         endothermic (absorbing heat). The solution cools rapidly hindering
                                         further dissolving.
                                   This bath should remain acidic for proper results.
                                   To maintain a low PH, Oxalic Acid may be added, but is rarely needed.
                                   Never allow any HCl, H₃PO₄, or other clearing bath acid to contaminate
                                        this bath.
                                   A fresh solution may be seasoned by putting in a couple droppers full of the
                                        platinum solution
                                   Replenish with fresh stock solution as needed, but start over with fresh
                                        solution when heavily used to prevent fogging.

      Ammonium Citrate
                   Developer
                                   This developer produces a very neutral color.
                                   But, it can produce a slightly flat looking print.
                                   Flatness can be avoided while achieving a more neutral color by mixing
                                        with Potassium Oxalate (50-50.)
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      Phosphoric Acid
                    Clearing Agent
                                   Clear liquid, usually 85% reagent grade
                                   An excellent alternative to HCl. This bath will not bleach the image and
                                        works great.

      Hydrochloric Acid
                    Clearing Agent
                                   Clear liquid, it is recommended to use the 18-20% solution named
                                        Muriatic Acid.
                                   High concentration is hazardous and should be used only with the proper
                                        equipment and precautions.
                                   This is the traditional clearing bath. But, the traditional clearing times are
                                         in error.  See section on clearing.
                                    Works fine for some papers and fabric, but can bleach the image when
                                         using longer clearing times necessary for most of the thicker papers.

      Citric Acid
                     Clearing Agent
                                    White crystal
                                    An alternative to the other acid clearing agents.

      Sprint Fixer Remover
                      Clearing Agent
                                     Liquid colored with blue exhaustion indicator.
                                     One of the fastest clearing agents for most papers.

      EDTA(Na4)
                     Clearing Agent
                                      White powder
                                      Clears only when EDTA and Oxalic Acid are added to the sensitizer.

     Sodium Sulfite
                     Clearing Agent
                                    White crystal

      Sodium Bisulfate
                     Clearing Agent
                                     White crystal

      Baking Soda
                      Neutralizing Agent
                                       White powder
                                       Add diluted acid (working solution) to baking soda and water to neutralize.
                                       Do NOT add straight to any acid. This is NOT intended for acid spills.

        Note:    More information on how individual clearing agents effect the print can be found
                      in the Clearing Study.
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------------------other chemicals----

       Potassium Ferricyanide
                      Testing Agent
                                        Red or deep red-orange crystal
                                        This will harm platinum-palladium chemistry, even in the tiniest amount.
                                        Be careful and clean when using.
                                        Store in a location separate from any platinum-palladium chemistry.

 
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