After you dissolve 4 grams of ammonium ferric oxalate crystals in 8 ml of distilled water, top the solution off to 10 ml and pour it into a stopped brown bottle. Add ascorbic acid solution (1% for gold or 2% for palladium and/or platinum) to the bottle of 10ml of 40% ammonium ferric oxalate (or of sodium or lithium ferric oxalate). As I describe repeatedly in my videos and online articles, remember that you have to shake the bottle vigorously -- for 15 to 30 seconds -- to disperse the ferrous iron subsequently created evenly throughout the solution. Otherwise, the ferrous iron will simply precipitate out of solution and fall to the bottom of the bottle: you likely won't get satisfactory results when you attempt to print with a solution of AFFO in that state. I apologize to the general community, as I have been guilty of assuming everyone knows that when you add one chemical or compound to another when preparing a solution (for alt process printing) you generally shake or stir the admixture to get it into a proper solution. However, I encountered recently a rather unpleasant person in of all places the APUG forums who could not make a print in palladium because no one had ever explained this fundamental concept to him.
I have found the best prices for iridium and ruthenium to be had at ArtCraft Chemicals iridum and ruthenium in 5 gram units and Pressure Chemical Company Iridium by the gram and Ruthenium in 10 gram units. Read on to understand why I mention this. Purchase iridium(III) chloride hydrate and ruthenium(III) chloride hydrate. Dissolve directly in distilled water at 20% or less working strength for iridium and 10% or less for ruthenium.
Ruthenium is a member of the platinum metals group. Although ruthenium is extraordinarily rare, the price is relatively low, lower than palladium. Although ruthenium will not print out fully on its own, not even with a double ferric ferrous oxalate, it has three big applications for photographing printing:
Prepare fresh ammonium ferric oxalate as for dry print out with palladium, as above with 8 drops 2% C added to the 10 ml 40% ammonium ferric oxalate IN THE BOTTLE. Shake the bottle for 30 seconds! You have 10ml AFFO(8:2%C). Label it.Altneratively, mix up a fresh solution of lithium ferric oxalate (or buy some from Bostick & Sullivan). (For Mr. Sullivan's lithium ferric oxalate formula, go here B&S Articles and scroll down to the All About Ferric Oxalate link and click that.) I mix my own from oxalic acid, ferric oxalate and lithium carbonate (which I bought at a local glass making/pottery place where middle-aged, middle-class women go to learn how to make pots). Pour 10 ml into a brown bottle and add 8 drops of 2% C and shake vigorously. The lithium ferric ferrous oxalate is considerably contrastier than ammonium ferric ferrous oxalate and so you need to add less contrast booster
Prepare a solution of ruthenium by dissolving 1 gram of ruthenium(III) chloride hydrate in 10 ml of warm water (~90 degrees Fahrenheit). Dilute some of the solution 1:1 with water. Note: Ruthenium is available from Artcraft and a few sellers on Ebay. General price is $27USD to $30USD per gram, typically with a 5 gram purchase. I bought 5 grams for $145 including shipping. It mixes up to 50 ml.
To mix with palladium, for a 4x5 print, add 3 drops of the AFFO(8:2%C) to a shot glass. Count 3 drops 15% potassium palladium chloride OR lithium palladium chloride into the shot glass. Dilute 1 drop of 10% Ru 1:1 w/H2O to make a 5% solution. Add 1 drop to the palladium and AFFO. Depending on your negative's contrast, you may need to add anywhere from 1 to 3 drops of 26% ferric oxalate (NO ascorbic acid added!), or ammonium dichromate or Bostick and Sullivans Na2 contrast booster. Use whatever works for you -- on hand, cheapest, most dangerous, whatever. If you use lithium ferric ferrous oxalate you probably won't need to add any ferric oxalate (or other contrast booster). Swirl to mix thoroughly. Brush onto a sheet of Revere Platinum, 140 or 300 gsm, or onto Arches Platine, Canson Colorline, or other Pd-friendly paper. Do not be concerned if any precipitated ruthenium particles are present: they will break down during drying and subsequent exposure to UV. Place in dark to dry completely (~15 minutes).
Expose paper, by inspection, in frame in contact with negative.Print out is very fast with ruthenium, much faster than with gold, platinum, or palladium. I obtained a 15 second print out, in sunlight, with an older (~3 months) bottle of AFFO(8:2%C), and a 90 second print out with a fresh solution. When print out is slightly lighter (~1/3rd to 1/2 stop than desired) remove print from frame and immerse in 10% citric acid if colorline or Revere 140 gsm, in very weak (.5%) hydrochloric (muriatic) acid if Platine or 300 gsm Revere Platinum. Then wash in running H2O and continue clearing as for palladium. A print made using process as described:
The above print was slightly warm (a golden honey tint to it) and the contrast was much softer when still damp. Almost surreal smoothness. To preserve at least something of that, of course coat in gelatin while still damp and then harden with chrome alum.
Iridium is a noble metal of the platinum family. The master printer and photographer Irving Penn frequently mixed iridium with platinum and with palladium for his prints. Based on my results with iridium, I suspect Penn's motivation was to nudge print color toward neutral gray scale and also to deepen the Dmax of his prints. Warning: read the MSDS on iridium and take proper precaution with this metal.
This contact print, on Revere Platinum 140 gsm paper, illustrates the value of iridium as an additive to palladium (or platinum, or gold). The formula was 3 drops of ammonium ferric ferrous oxalate (8 drops 2% C added to a bottle containing 10ml of 40% ammonium ferric oxlate), 2 drops of 26% ferric oxalate (no C added), 3 drops 15% lithium palladium (potassium palladium would work equally well), and 1 drop 5% iridium. The image printed out fully at normal speed (~5 minutes in my 6 13w UV bulb box). It looks like a platinum print with a contrast boost more than palladium. Notice the amazing black of the model's eyes -- that is faithful to the original print.
As this 4x5 contact print shows, iridium is a vigorous medium. It also exhibits slight grain, more so than platinum (at least than the virtually grainless platinum obtained with my Fannintype, in which I use glycerin to constrain the grain). This image was made by mixing 2 drops of 10% iridium with 1 drop of 15% palladium. The sensitizer was 3 drops of ammonium ferric ferrous oxalate, of course, prepared with 8 drops of 2% C. An additional 2 drops of 26% ferric oxalate (no C) boosted the contrast nicely. Clearing was citric acid, water, t-edta, water, t-edta and a final wash. Paper was Bergger Cot 320 sized with gelatin.
I have previously developed out iridium with silver nitrate. The image was strong and vigorous as this one. Because of the grain, however, I expect to keep my use of iridium with palladium, platinum, and gold down to about 25% maximum of total metal solution. Tip: Ruthenium will smooth over any roughness or grain induced by iridium.