Ferric-Silver Formulae

Ferric-silver processes fall into two broad categories--those which contain ferric ammonium citrate and those which contain ferric oxalate.  Prints from the former are generally referred to as brown prints, sepia prints, or Vandyke Brown (VDB); and prints from the latter are generally referred to as kallitypes.  Some formulae contain both chemicals, however kallitypes generally require a developer whereas brown print is a printing out process.

Brown Print (Vandyke) Formulae

Today’s “standard” brown print formula adheres closely to the original formula patented by Arndt and Troost in 1895, and is found in a multitude of minor variations.  The gelatin is often omitted, since so many modern papers are already sized.  The very similar formula from Cassell’s Cyclopaedia of Photography (1911) recommends mixing just prior to use, whereas the usual recommendation today would be to mix A, B, and C and let the solution ripen for a day or more, then add the mixture to warm gelatine.  The oxalic acid formula substitutes oxalic for tartaric acid, but requires an alkaline solution to develop.  The downside of this is that an alkaline environment can cause the formation of iron hydroxide.  Since iron hydroxide is very difficult to remove, its formation is prevented by washing in a slightly acidic bath (a pinch of citric acid being added to the tray of water).  When Bob Schramm tested four different VDB formulas, including the oxalic acid formula, he concluded that the standard formula produced the best results.  Schramm did not test some of the more obscure early formulae provided by Dick Stevens in his definitive work Making Kallitypes.

Despite the fact that “Vandyke” has become established as the name for the brown print process, it is a misnomer.  Well into the 1930’s, the process was referred to variously as “brown print,” “sepia print,” and sometimes “Kallitype,” but never Vandyke.  Cassell’s Cyclopaedia lists it under “kallitype” and refers to it variously as a “modified kallitype” or “water-developing kallitype.”  The “Vandyke” process described in early 20th century photographic literature (see Cassell’s and Photographic Facts and Formulas) was a photo-lithographic process wherein zinc plates were coated with an enamel consisting of fish-glue, ammonium dichromate, and chromic acid.  The process, which was used primarily for copying maps, bears no relation to the brown print process of Arndt and Troost.  I have been unable to determine at what point “brown print” and “Vandyke” became synonymous.  The Encyclopaedia Britannica of 1961 lists Vandyke as a ferric-silver process, so the usage was established by that time.

A longstanding concern has been voiced about the archival qualities of the brown print.  This is due to the fact that many early brown prints did not last long, and my own experience bears this out.  The modern consensus seems to be that, if it is processed properly, the brown print will have the same longevity as any other silver process.  For the brown print there are four things to consider to assure print permanence:  (1) removal of iron compounds, (2) sufficient fixing, (3) sufficient washing, and (4) toning--not necessarily in that order.  My personal experience tells me that toning is not optional.  Untoned prints keep fine in a closed box, but once exposed to light and atmospheric pollutants, they begin to deteriorate almost immediately.

I have always used a 5% solution of hypo (sodium thiosulfate) to fix brown prints, but Russ Young (who wrote the Kallitype article in Coming into Focus) told me that a 2% solution was more appropriate.  At that dilution, I would think a liter would only be good for maybe two or three 8x10 prints, but I don’t have a definitive reference on that.  I prefer to use a two-bath fix regime, just to make sure.

According to Russ Young, removal of iron compounds in Kallitype is best accomplished by immersing the print for two minutes (with continual agitation) in a 3% solution of citric acid, after all other processing is completed, followed by a one minute running water wash.  For brown prints, Wynn White recommends continuous agitation in successive water baths, each with a pinch of citric acid added.  I have noted that the print is reduced somewhat during this washing process, but regains a greater contrast range in the fix.  If citric acid is not used in the wash baths, a final rinse in a 3% citric acid bath is a good idea for the brown print.

Washing should be thorough.  Wash times can be reduced by a 3 minute immersion in hypo clearing agent with continuous agitation.

Various additives may be used with the brown print.  Print colour can be influenced somewhat by the addition of a drop or two of 1% gold chloride, 1% potassium chloroplatinite, 1% sodium chloropalladite, or 5% uranium nitrate.  If a precipitate forms, filter it out.  Image colour is affected much more by final toning than by additives to the Vandyke solution.

Contrast is traditionally increased by the addition of a drop or two of various concentrations of potassium dichromate (1-5 %).  The strongest concentration gives about a one-half stop increase in contrast.  Ferric citrate is more effective (see James Thompson’s formula and the Photo-Miniature formula).  3 to 6 grams of ferric citrate can be substituted for ferric ammonium citrate in the brown print formula.  The ferric citrate rarely dissolves completely.  To help dissolve the ferric citrate, the water can be heated to 140° F and additional tartaric acid added.  I generally stir the mixture for as long as I can stand it, then let it sit overnight and filter out the remaining undissolved ferric citrate.  The ferric citrate Vandyke formula can then be mixed with the standard Vandyke formula in various proportions to adjust contrast.

Alternatively, you can make a ferric citrate stock solution.  Heat 25ml distilled water to 140° F.  Add 3 grams ferric citrate and stir.  Add 0.5 grams tartaric acid and additional hot distilled water to 33ml.  Stir.  Allow to sit overnight and filter.  To increase contrast, 1 to 5 drops of this solution can be added per milliliter of Vandyke solution.

For ease of coating, I usually add a drop or two of 5% Tween-20 solution to each coat, and sometimes a drop or two of 14 baume gum arabic solution.

Very simple toners can be made for brown prints by making a 0.5% solution of citric acid and adding 10 to 20 drops of 1% gold chloride, 1%  potassium chloroplatinite, or 1% sodium chloropalladite.  Not much metal salt is necessary for brown print toning, since the silver particles in the print are very fine.  These toners are usually used after the wash and before fixing, but may also be used after fixing, if desired.

Selenium toning is best done after fixing, since selenium tends to have a slight reducing effect which is much more pronounced if toning is done before fixing.  Simply mix 3 to 5 milliliters of Kodak Rapid Selenium Toner in a liter of water.

Kallitype Formulae

The Kallitype process, in three variants known as I, II, and III, was patented by W.W.J. Nicol between 1889 and 1891.  The K I patent, applied for in 1889, has a ferric salt sensitizer, while the developer contains silver nitrate.  The K II patent, applied for in 1891, has both a ferric salt and silver nitrate in the sensitizing solution, while the developer merely expedites the formation of image silver.  The K III process combined all necessary chemicals in a single solution, and printed out fully if the paper were damp, but K III never proved feasible in practice, apparently plagued by inconsistent results.  Nicol never patented the K III process, but outlined it in his K II patent.

Many variations on the Kallitype process have been published since Nicol’s time.  James Thomson gives some interesting variants of both K I and K II in the Photo-Miniature numbers 10, 47, 69, 81, and 185. He eventually settled on a K I process.  The Kallitype II is probably most practiced today, though James Thomson claimed his K I process gave a blue-black tone closer, I presume, to that of the bromide silver gelatin print.  The big downside to Kallitype I is that silver in the developer is depleted with use, so one can have difficulty obtaining consistent results, and one is far more likely to waste expensive silver nitrate.

Kallitype prints can be coated and processed under a yellow bug light with no problems.  They seem to be sensitive only to the ultraviolet spectrum.  Kallitype sensitizer is easily contaminated by very small amounts of metal or other chemicals, so mixing vessels, trays, syringes, coating rods, brushes, etc. must all be kept scrupulously clean.  Trays can be cleaned with muriatic acid, available at most hardware stores for cleaning cement.  Just pour it into the tray for a few seconds, then back into the bottle--it can be reused again and again.  It is usually best to mix developer and toner with distilled water.  Some practitioners use distilled water for all solutions.

Development:  Full development of a Kallitype II print is important, because a lot of the iron salts are removed during development.  The image doesn’t gain much density after the first minute, but I usually give at least 5 minutes development time, and 10 is not unreasonable.  Dick Stevens recommends adding up to a gram of tartaric acid to the developer after each print.  This inhibits the formation of insoluble iron salts in the developer.  I’ve had good results with this regime, though it warms the print considerably.  10% Sodium acetate developer, with a single gram of tartaric acid, gives nearly black tones which become quite brown with the addition of more acid.  Stronger solutions of sodium acetate appear to give even blacker tones, whereas more dilute solutions give warmer tones.  Sodium citrate also works very well as a developer, but gives warmer tones than acetate.  For test strips, I simply develop for 30 to 60 seconds, and don’t bother with further processing.

Restrainer:  I add 3 to 6 milliliters of 3% or 5% potassium dichromate per liter of developer, as necessary for the negative to hand.  It acts as a restrainer, keeps the high values from blocking up, and in larger quantities increases contrast.  Print times will increase somewhat with greater amounts of dichromate.  Only my most contrasty negatives print well in a developer with no dichromate added.

Clearing:  Making kallitypes is a constant battle against stain caused by residual iron compounds--proper clearing is essential to archival quality.  The print should be rinsed in water after development, and it is important to make sure this rinse is either neutral or slightly acidic, as an alkaline rinse will cause the formation of ferrous hydroxide compounds that are almost impossible to remove.  I use two 2 minute rinses, with continuous agitation, in tap water with a generous pinch of citric acid added.  I follow these rinses with at least 5 minutes in a clearing bath of 3% citric acid or 1.5% EDTA.  Finally, I wash the print for two minutes in running water before toning or fixing.  In some cases I have found the EDTA bath to clear more effectively than citric acid.  I extend the the time in the clearing bath to 10 or 15 minutes, as necessary, to eliminate stains.  If the clearing bath becomes ineffective, it should be changed.  Clearing reduces the print somewhat, but most of the image comes back in the toner.  If stain appears after toning or fixing, the print can be returned to a fresh clearing bath for as long a time as necessary.

Toning:  When a noble metal toner is to be used, it should be used before fixing, particularly if a color change is desired.  If selenium is to be used, it is better to fix first.  Using a noble metal toner after fixation allows greater retention of the native color of the kallitype  (which, of course, varies with the developer used).  You will want to print darker, if you fix before toning, because fixing an untoned kallitype can reduce density by up to a stop, depending on the developer used and other processing variables.  Stevens recommends giving 20% more exposure than that required to produce the desired print density in the developer, when fixing before toning.  You must clear completely and wash thoroughly before and after fixing, to prevent stain from selenium.  The kallitype tends to form selenium stain wherever sensitizer was coated onto the paper.  Only thorough clearing and washing reduces this tendency to stain.  Platinum or gold stain less than selenium, but must still be cleared and washed sufficiently, or some stain may appear.

Fixing:  Another possible cause of stain from selenium is inadequate fixation.  Some practitioners recommend fixing in a 2% bath of hypo (sodium thiosulfate) for 10 minutes.  Others favor a more concentrated bath of 5 or 5.5% hypo for 2 to 5 minutes (one liter is good for five 5x7 prints).  I’ve settled on two fixing baths of 5.5% hypo, and I give continuous agitation in each bath for 1 to 2 minutes.  With the two bath method, I fix a conservative four 8x10 prints per liter of hypo.

>