Illustration 5.
Mexican Artillery
Position, San
Jacinto, Texas.
Pure palladium.

Palladium is a genial metal, at least as impervious to atmospheric pollution as gold and platinum, and that actually encourages platinum and gold alike to print out. It has slightly more latitude than platinum or gold (when the gold is a  Chrysotype Supreme). Palladium seemingly gives itself to almost any paper and, with ascorbic acid, no paper humidification is necessary.

Like the Ziatype, this process uses a 15% solution of palladium, although the printer is encouraged to experiment with solutions in the 10% range. Unlike the Ziatype process, which depends on hydration of the paper, the Palladiotype Supreme process also works perfectly well with sodium palladium or potassium palladium. (There is minimal cost-saving in selecting one over the other.) Lithium palladium has the advantage of being available from Bostick & Sullivan in a freshly mixed solution; you have to mix your own sodium palladium and potassium palladium. (Remember when preparing a palladium solution to add half a gram of sodium chloride for each gram of palladium to get the metal to dissolve completely.)

The Palladiotype Supreme is so easy that only one person is known ever to have failed to obtain print out of an image in palladium on first attempt, and that was an intellectually challenged APUG forum troll who disappeared from the internet entirely a few months later. 

With this process, a pure palladium print requires adding the appropriate number of drops of palladium to a solution made up of 8 drops of 2% ascorbic acid added to 10 ml of 40% ammonium ferric oxalate – AFO-C(8:2%). You can also use sodium ferric oxalate or lithium ferric oxalate, both of which have higher inherent contrast than ammonium ferric oxalate. (Dick Sullivan included the formulas for both the sodium and lithium varieties in his article All About Ferric Oxalate in the articles section of the Bostick & Sullivan web site. The ingredients are easily obtainable and inexpensive -- with the possible exception of ferric oxalate to printers in the UK.) The author has successfully printed a number of palladium prints with lithium ferric oxalate, treated with 8 drops of 2% ascorbic acid. The neutral gray image usually prints out very quickly in a UV box or in direct sunlight.


Contrast: If needed, boost contrast

Clearing: If printing on heavy papers, such as Arches Platine 320 gsm, immerse the print in three successive .5% hydrochloric acid baths. This clears virtually all of the iron (including the yellow stain from the ferric oxalate, if that is used for the contrast boost). The final bath is 10% sodium carbonate, which raises the PH. Sodium hydroxide is an acceptable -- albeit caustic -- alternative to the carbonate.

If you are printing on a light paper, you can substitute a 10% citric acid solution for the hydrochloric acid. After the acid baths, clear the paper in two successive baths of 10% T-EDTA. The final alkaline bath is not necessary.  


Because contrast control is so flexible, any negative prints with the Palladiotype Supreme. Small format negatives are easily enlarged onto white light sensitive x-ray duplicating film. The film is available up to 14"x17" and is quite inexpensive (~$1.75 to $3.00 for each 14x17 sheet). Control contrast of the final negative with the developer. Caffenol LCC (low contrast caffenol) yields extremely soft negatives at normal exposure and reduced development time; standard caffenol (more C and more coffee) sharply boosts contrast in negatives. In effect, use Caffenol with more vitamin C to raise constrast in the film being developed

The digital photographer, working with an inkjet negative, will find the Palladiotype Supreme the ideal medium for printing. Chemical-based contrast solutions can be dispensed with and an appropriate photoediting curve applied to the negative.


For an 8x10 print, count 20 to 24 drops of AFO-C(8:2%) into a shot glass, add the same number of drops of lithium, sodium or potassium palladium, and swirl to mix the two thoroughly. If the negative is reduced contrast, as for printing with silver gelatin paper, count 5 drops of 26% ferric oxalate into the shot glass and swirl the liquid until completely mixed. 

Warning: Do not add hydrogen peroxide to boost contrast as it will restore the ferric iron in the ammonium ferric oxalate and the image will not print out.


Arches Platine is strongly recommended for this process, especially for beginning printers. Suitable papers in general are:

Not tested by the author but reported by various sources to print out with palladium:

Good venues for purchasing paper are Freestyle Photo, Adorama, Utrecht Art, and Talas (for the harder to find ones), Hobby Lobby, and, locally, well-stocked art supply stores.

Palladium Chloride

Print with either 15% lithium palladium chloride, potassium palladium chloride (potassium tetrachloropalladate) or sodium palladium chloride.  Lithium palladium, which is the form of the metal specified for the Ziatype process, is available in a premixed 15% solution from Bostick & Sullivan. You can purchase sodium or potassium palladium from any of several suppliers, such as Artcraft Chemicals in Altamont, NY, and prepare your own solution in any strength (up to the 15% saturation solution). When preparing a palladium solution add half a gram of table salt for each gram of the metal salt before adding warm water (80° F to 90° F). If the salt is not added, the palladium will not go completely into solution. Prepare a 15% solution by dissolving 1 gram potassium palladium chloride and .5 gram sodium chloride in 6 ml warm distilled water.  IMPORTANT: The temperature of the water must be between 80 degrees Fahrenheit and 90 degrees Fahrenheit. Members of the Photrio Analog forum should ask their parents to help them.


All of the chemicals required are readily available from a variety of suppliers in the United States, Asia and Europe. With the exception of muriatic acid, which is severely caustic and burns flesh and can scar or blind if splashed in the eyes, none of the chemicals are particularly dangerous unless grossly mishandled (that is, swallowed or inhaled). Adults capable of mixing up ammonium ferric ferrous oxalate should be able to handle muriatic acid safely. Citric acid is an alternative to muriatic acid, at least with lighter weight papers. 


Prepare solutions with distilled water. Distilled water is free of the chemical contaminates (including iron) and particulate matter found in tap water.

Caution: wear a good dust mask when preparing solutions as accidental inhalation of any of these chemicals (except ascorbic acid) can have serious health consequences.


Use only AFO-C or LFO-C prepared at a strength of 8 drops of 2% ascorbic acid added to a bottle containing 10ml of 40% ammonium ferric oxalate (and shaken quite vigorously for at least 15 seconds) for this process. If needed, boost contrast with 26% ferric oxalate. A typical amount needed for a soft negative you probably would print on grade 2 silver gelatin would be 4 to 6 drops of ferric oxalate for an 8x10 print. With a stronger negative, or if you choose to print with lithium ferric ferrous oxalate (LFO-C), prepared in the same manner as the ammonium ferric ferrous oxalate, a contrast boost is often not needed.

Finer control of contrast is afforded by adding a drop of 13% ferric oxalate in addition to the 26% ferric oxalate. Contrast steps are then half so great as with a 26% solution.

Contrast Table

The following table assumes a low contrast 8x10 negative. Remember, the ferric oxalate is in addition to the ~ 20 drops of AFO-C(8:2%) and 20 drops of palladium.

Contrast With AFO-C(8:2%) and 26% Ferric Oxalate
Ferric Oxalate Contrast
4 drops Low
5 drops Low medium
6 drops Medium
7 drops Medium high
8 drops High

As a general rule, use the same number of drops of AFO-C (SFO-C or LFO-C) as of palladium. 20 drops of metal salt will usually suffice for an image; some may discern an acceptable image with less metal salt; increase the sensitizer drops as well. Also note that using less sensitizer than metal reduces contrast. 

To make an 8x10 print:

1. Don a pair of rubber or nitrile gloves.
2. Working in weak tungsten light, count 18 to 24 drops of 40% AFO-C(8:2%) into a shot glass.
3. Add 18 to 24 drops (an equal count to the AFO-C(8:2%) of 15% palladium.
4. Holding the damp brush in one hand, swirl the liquid in the shot glass vigorously and pour the sensitizer solution onto the paper just outside the sketched negative area.
5. Brush the solution quickly but methodically, vertically, horizontally and diagonally across the paper. Spread the solution out evenly as fast as possible while keeping it more or less within the outline. Tip: Perfect your brushwork on ordinary paper using glycerin mixed with food color before trying this with the precious metals.
6. Place the sensitized paper in a dark, dry, cool place for 15 to 30 minutes, until dry. On very humid days, a print takes longer to dry. Do not be tempted to print until the sensitizer is dry.
7. Place a sheet of 2 or 3 mil mylar/acetate on top of the dry paper and the negative on top of the mylar. Place all in the contact print frame.
8. Expose in direct sunlight or to a UV light source. Anticipate exposures ranging from less than 1 minute to as long as 15 minutes, depending on the density of the negative. Keep an eye on the over brushed sensitizer extending past the negative. When it turns dark gray, drop one side of the print frame back to view print-out progress. (Note: Ferric oxalate stains the paper dark yellow, and the image therefore appears darker than it actually is. Examine the print carefully for detail in the darkest and lightest zones where you want detail. Tip: Minimize the interference of the stain by viewing the print through a yellow filter.
9. Immerse the correctly exposed print in a first bath of iced (~35 degrees Fahrenheit) tap water. This ice water bath minimizes the initial darkening of the image.
10. After five minutes, pour off the cold water and pour 250 ml to 500 ml of .5% hydrochloric acid into the tray. Agitate intermittently for five minutes.
11. Discard the acid and wash in cool running water for five minutes.
12. Repeat the .5% acid bath with fresh solution and water wash two more times.
13. After the third wash in running water, pour 10% calcium carbonate or sodium carbonate into tray. Agitate intermittently for 15 minutes.
17. Wash a print on Arches Platine or Revere Platinum 300 gsm in running water for 60 minutes. Wash Revere Platinum 145 gsm or Clear Print vellum for 30 minutes.
18. Drain the print holding it by one corner and hang to dry. Do not touch the emulsion.
19. Spot the dry print with spot tone or India ink as necessary.

Problems and Solutions

Problem: I tried adding 4 drops of 26% ferric oxalate to my 40% ammonium ferric oxalate but the contrast in my print is still too low.
Solution: Depending on how much more contrast is needed, add 1 drop to 3 drops of 26% ferric oxalate to the sensitizer. If a significant contrast boost is not apparent in the next print, the AFO-C has gone bad (or is the wrong strength) or the ferric oxalate is old (and weak), or the UV lamps are fading. Finally, you may need much higher contrast: prepare a solution of lithium ferric oxalate, and add to that the 8 drops of 2% C (and recap and shake the LFO vigorously to disperse the C throughout the solution); add 26% ferric oxalate to the mixed sensitizer if needed. 

Problem: My prints fade in the hydrochloric acid bath.
Solution: The acid is too strong. For pure palladium prints, the maximum strength is .5%. A strong solution of hydrochloric acid dissolves finely divided palladium. (Remember when diluting muriatic acid that its full strength is approximately 30%. So 100 ounces of water added to 1 ounce of muriatic acid yields a .3% solution.)  Alternatively, use a lighter paper -- less than 200 gsm -- and replace the muriatic/hydrochloric acid with citric. 

Problem: My prints slowly get darker and after a few weeks are almost entirely black.
Solution: This is caused by insufficient clearing of the iron. Leave the print in the hydrochloric acid baths longer. You might try adding a bath in 10% tetrasodium EDTA between the hydrochloric acid baths (with additional water washes). Make sure that the final water wash is 60 minutes for heavier papers (250 gsm and heavier) and 30 minutes for lighter papers.

Problem: My prints look gritty and the image does not completely print out.
Solution: You are using an incompatible paper. The sensitizer soaked too far into the fibers. Refer to the papers list above and choose one suitable for this process. If you cannot find a suitable paper, you can size an otherwise unsuitable one with either Knox gelatin or arrowroot starch (or liquid starch which is typically made with corn starch). Iron the paper before sizing, then let  the sized paper dry thoroughly before use.

Problem: I get dark stains in my paper where I pour the sensitizer solution.
Solution: Arches Platine is the recommended paper for this process. Only AFO-C(8:2%) – 10 ml of 40% ammonium ferric oxalate with 8 drops of 2% ascorbic acid added – is appropriate. Higher volumes of 2% ascorbic acid precipitate the metal faster. Also take care to brush the solution across the paper as fast as possible. Try spreading the sensitizer with a glass coating rod. If you have trouble with the "re-invented" rod with a paddle glued to it, you can use  a No. 28 Mayer Rod of the type used by printers for centures (refer to 

Problem: My image is too contrasty.
Solution: Add less ferric oxalate to the sensitizer.

Problem: My image is blotchy and grainy.
Solution: Either you used the wrong paper or you humidified the paper. Use a paper known to work with palladium (refer to the list above) and do not humidify.

Problem: My print looked fine after clearing but when it dried it turned yellow.
Solution: Clearing was insufficient. Try adding 50 ml of Lime Away to 950 ml distilled water. Give the print two 10 minute baths with 10 minutes baths in running water interposed. If that does not work, try Rit Color Remover, which contains sodium hydrosulfite (sodium dithionite). The non-bleaching chemical will not damage paper.