The Texas Palladium

The Texas Palladium-Platinum Process:
Notes on Dry Print Out with Platinum and Palladium

by Richard Eugene Puckett

Note: the chemicals and metals discussed in this article are toxic and should be kept out of reach of children and animals. Wear rubber or nitrile -- not latex -- gloves while working with them.  Wear a good respirator to avoid inhaling the metal particles if you mix your own platinum or palladium solutions from powder.  Never use a blow dryer or fan to speed up drying sensitized paper (because you do not humidify paper for this process, prints air dry very quickly).

Following on my Texas Chrsyotype process, in which I treat ammonium ferric oxalate with ascorbate to print out grainless pure gold images with a latitude of 10 to 11 stops, I turned my attention to palladium- platinum.  Dick Sullivan's (of Bostick & Sullivan ) Ziatype process has become possibly the most popular fine art printing process in the 21st century.  The Ziatype has a long track record for yielding excellent results.  However, I found the process improvable in two ways: the humidification of paper, which is difficult to quantify and introduces a level of uncertainty in the printing process, and the limitation that no more than one third of the palladium be replaced with platinum.  The Texas Palladium-Platinum process, like the Texas Chrystoype and the Karytype (gold-platinum), replaces humidification with modification of the sensitizer.  Further, I found that by freezing and thawing a platinum solution, I could substitute platinum for at least 75% of the palladium.

Whereas 8 drops of 1% ascorbate added to 10 ml of 40% ammonium ferric oxalate works fine for printing with pure gold, platinum and palladium need a bit more coaxing to precipitate out of solution properly in the absence of humidity.  I arbitrarily doubled the strength of the ascorbate (to a 2% solution) and added the same number of drops to the 40% AF0.  The results were promising, but the images were still flat.  I then began adding other chemicals to the AFO-C and quickly saw that with ferric oxalate my goal of a dry print out process for palladium and palladium-platinum was at hand.  Furthermore, I could even substitute platinum for up to 75% (or more) of the palladium.  By 100% platinum, the formula changes and taming platinum's grain becomes the new issue.  (For those reasons, pure platinum print out will have to wait for a separate article.)

The chemicals I have successfully used for boosting the contrast with palladium and palladium-platinum are:

• ammonium dichromate
• ferric oxalate
• more ascorbate added to ammonium ferric oxalate

Ammonium dichromate is an extremely hazardous chemical that can induce various cancers and failure of vital organs.  It also increases print out time exponentially.  In my opinion, dichromates do not belong in the darkroom.  For these reasons, I do not recommend using ammonium dichromate to boost contrast.

At worst, ferric oxalate gives the print a yellow cast that easily clears.  Used in combination with ascorbate-enhanced ammonium ferric oxalate, the volume of ferric oxalate can be kept to a minimum.  To do so, increase the volume of ascorbate you add to the ammonium ferric oxalate.  Some negatives - those of medium to high contrast -- may not even need ferric oxalate added to the sensitizer.  This allows the printer greater control over contrast by increasing or reducing the volume of C in the ammonium ferric oxalate; the printer is therefore encouraged to prepare several solutions of ammonium ferric oxalate-C with as few as 8 drops of 2% C to each 10 ml to as many as 14 drops of 2% C added.  Low contrast negatives will always need at least one drop of ferric oxalate.

Fundamentals of the Texas Platinum-Palladium Process

The iron-based processes use ammonium ferric oxalate and a metal salt (for example, potassium palladium chloride) to form an image. On exposure to a UV light source, the oxalate releases an oxygen atom from the iron, converting it to its ferrous state. The iron precipitates out of solution onto the paper, taking palladium and/or platinum with it. The exposed print is subsequently cleared of the iron to leave behind an image formed entirely of the noble metal(s).

By adding 6 to 14 drops of 2% ascorbate (vitamin C) to 10 ml of 40% ammonium ferric oxalate, you create an alchemical iron that exists simultaneously in its ferric and ferrous state: AFO-C. A print from this amalgam is self-developing during exposure on dry paper that needs no pre-humidification. Palladium (and platinum) drops out more efficiently than with the traditional damp ammonium ferric oxalate process. In addition, for the first time -- ever -- with AFO-C one can print an image formed from gold and platinum (like pure platinum print out, the Karytype will have to be the subject of a separate article).

Tools You Need

You need the same equipment that is used for any of the 19th century alternative printing processes:

• Synthetic (not hake) brush one-quarter to one-half the width of the negative to print (such as, 2" to 4" brush for 8x10)
• Contact print frame. (You can make one from a heavy sheet of plate glass clamped, with potato chip bag spring clips, to a split back made of plywood.)
• Tray larger than your prints
• Stirrer
• Paper towels
• Shot glass (from which you will never drink again!)
• Pencil
• Scale sensitive down to 1 gram
• Rubber or nitrile gloves (NOT latex)
• UV light source -- either the sun or a UV box
• Graduated beakers or cylinders -- one up to 25 ml and a second up to 1000 ml
• 10 ml to 30 ml transparent brown glass bottles with stoppers
• Various 1 liter bottles with air-tight caps
• Adhesive labels
• Water-resistant labeling marker

Papers You Need

Use cold pressed unsized or internally sized pure rag cotton paper. I have obtained superb platinum and palladium images on:

• Arches Platine (internally sized)
• Revere Platinum (unsized)

Of the two, I far prefer Revere Platinum 300gsm. It usually loses its stain in the first water bath, and images printed on this unsized rag cotton paper are crisp and pure. Arches Platine by contrast has a tendency to show a hint of grain and softness in low -contrast prints made with platinum present in the palladium, and requires a stronger first acid bath followed by aggressive baths of tetrasodium EDTA and hypo clear.

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