Electrum: a naturally occurring amalgam of gold and silver. The ancients used electrum for jewelry, the Byzantines in particular minting electrum coins today prized by collectors and museums. An Electrumtype is a photographic print made with that amalgam.
The Electrumtype is a process inspired by Marek Mateusz' Satista formula for palladium or platinum developed out with silver nitrate. Gold is, of course, not platinum or palladium and a different approach is needed to reduce gold chloride to its elemental state. Ammonium ferric ferrous oxalate (AFFO), prepared for gold by adding 8 drops of a 1% solution of vitamin C to 10 ml of 40% ammonium ferric oxalate in a bottle, followed by vigorous agitation, is the key to reducing gold. To prepare an Electrumtype, considerably less gold is used than for the (pure gold) Texas Chrysotype.
Figure 1. Electrumtype exposed properly and ready to develop out fully in silver nitrate.
One-quarter to one-half as much gold is used for the Electrumtype as for the Texas Chrysotype. The volume of ammonium ferric ferrous oxalate (AFFO) remains the same as or a little more than for a print prepared as for a Texas Chrysotype. An 8x10 Electrumtype, for example, needs just 3 to 6 drops of 10% gold (instead of the usual 12 drops) and but 18 to 21 drops of AFFO.
After the weak image in pure gold is printed out, it is developed in a solution of 2% to 4% silver nitrate (AgNO3). The development is effected by pouring the silver nitrate onto the paper just outside the image area and then brushing (or squeegeeing) it quickly and evenly across the surface of the image. For an 8x10, I generally mix 15 ml of 4% silver nitrate with 15 ml of off-the-shelf corn syrup. The syrup thickens the solution, thereby minimizing the risk of splashes (which speckle the final print) and generally making it easier to spread the silver nitrate-corn syrup developer evenly.
The final print exhibits smooth tones with a wide latitude. The print color varies from paper to paper but is basically neutral with overtones of soft brown, or with a blue cast. It often exhibits purplish staining, but that staining and the blue cast can be minimized, if so desired, with a first bath in weak (0.5%) nitric acid. Be aware that nitric acid dissolves silver (it is the acid of the proverbial "acid test"), and so keep the solution weak and only leave the print in the acid long enough to reduce the staining.
The clearing process is a hybrid of that for all the iron-based processes and for silver gelatin prints: an initial soak in acidic water (typically, a pinch of citric acid in a liter of water) prepares the print for a bath in tetrasodium EDTA which is followed by a brief running water wash. Next the Electrumtype should be toned (face down in gold to increase the ratio of gold to silver, or in any other noble metal, such as palladium, platinum, rhodium, ruthenium, osmium, or iridium). Remember that an Electrumtype made with one-third to one-quarter as much gold as is used for a Texas Chrysotype is going to have proportionately less gold; it will be more silver than gold and susceptible to degradation. For that reason, toning, which will replace some or most of the silver with a nobler metal, is recommended. Purists will want to tone with gold. I myself prefer iridium as a toner; others may prefer the softer results obtained with palladium. If the print is toned, it needs to be washed again. After the washing, fix the print in very weak fixer -- 1 part fixer to 20 parts water -- for about 3 minutes (at this time, an over-exposed print may be lightened by using a stronger fixer, such as at a ratio of 1 to 10 fixer to water or even 1 to 5. The thiosulfate dissolves the metallic silver, so use caution.). After another wash, the print may be further cleared in sodium sulfite (Hypo Clear) and then a final wash 30 to 60 minutes finishes the process.
Figure 2. Electrumtype Kary fully developed out with silver. (Note: the slight grain is not present in the original print, nor in the scan of that print; it is an artifact generated when the image was uploaded to the server.)
Suitable papers for the process are the same as for the Texas Chrysotype:
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 stoppered 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.