Ferric-Silver Formulae

by Ed Buffaloe

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.

  

Original Arndt and Troost Brown Print Formula Ammonio-citrate of iron 80 to 100 grams Silver nitrate 12 to 20 grams Tartaric acid 15 to 20 grams Gelatin 10 to 15 grams Water 1 liter “Standard” Modern Vandyke Formula A. Green ferric ammonium citrate 9 grams Distilled water 33 ml B. Tartaric acid 1.5 grams Distilled water 33 ml C.  Silver nitrate 3.8 grams Distilled water 33 ml Combine solutions A and B slowly; add C while stirring.  Store in a brown glass bottle.  The formula should be allowed to “ripen” for several days before use.  This formula keeps almost indefinitely.  If it forms a precipitate, filter before use. from The Encyclopedia of Photography A.  Green ferric ammonium citrate 252 grams Water to make 1 liter B.  Tartaric acid 41 grams Water to make 1 liter C. Silver nitrate 106 grams Water to make 1 liter D. Gelatine 69 grams Water to make 1 liter The A and C solutions keep well in the dark; the B solution keeps for a few days only, owing to the formation of mould; while the D solution should be made just before use, the gelatine being soaked in the water and dissolved by heat.  Equal parts of the four solutions added together form the sensitiser; A and B solutions should be added to the warm gelatine D, the whole being kept warm by placing the measure, say a 10 ounce graduate, in hot water.  The C solution is then added very slowly, stirring the combined mixture with a glass rod the while.  The warm solution is then coated upon the plain paper, and as soon as the coating has lost its wet appearance and begins to look dull the paper is hung up in a warm room and out of the way of actinic light to dry; when dry it is ready for printing. Oxalic Acid Formula Green ferric ammonium citrate 24 grams Oxalic acid 4 grams Silver nitrate 10 grams Distilled water 300 ml Mix the ferric ammonium citrate and oxalic acid well, then add the silver nitrate.  Develop in a 1% borax solution.  Another source says to develop with 1 teaspoon of sodium sulfite in a quart of water. Vollenbruch Formula Sol. 1: Distilled water 100 parts Gelatin 0.5 parts Salicylic acid 0.05 parts Sol . 2: Distilled water 100 parts Green ferric ammonium citrate 20 parts Sol. 3:  Distilled water 80 parts Silver nitrate 10 parts Sol. 4:  Distilled water 100 parts Uranium nitrate 20 parts Developer: Distilled water 700 parts Ferrous sulfate 30 parts Acetic acid 10 parts Vollenbruch’s standard mixture was two parts each of Solutions 1 and 2, and four parts each of Solutions 3 and 4.  More of Solution 2 produces greater contrast, whereas more of Solution 3 produces less.  More of Solution 4 produces blue-black tones, whereas less of 4 produces browner tones.  James Thomson’s Formula Salt: Citrate of iron & ammonia  20 grains Ferric oxalate 12 grains Oxalate of potassium 12 grains Chloride of copper 6 grains Oxalic acid 4 grains Gum arabic 10 grains Distilled water 1 ounce Sensitizer:  Silver nitrate 50 grains Oxalic acid 2 grains Citric acid 20 grains Distilled water 1 ounce Coat paper with the salt solution and dry.  Coat with the sensitizer and dry with heat.  Expose the print until half tones appear, and develop in running water for 3 minutes.  Fix in 50 grains of hypo to a quart of water.  Additional ferric citrate can be added to the sensitizer to increase contrast. from The Photo-Miniature #10 A. Ferric citrate 50 grains Ferric oxalate 25 grains Distilled water 1 ounce B.  Silver nitrate 25 grains Distilled water 1 ounce Combine A and B and shake well.  Filter any precipitate.  Fix in a 2% ammonia solution. Namias’ Formula A.  Green ferric ammonio-citrate 44 grams Citric acid 10 ml. Distilled water 100 ml. B.  Silver Nitrate 11 grams Distilled Water 40 ml. Mix A and B and top up solution to 200 ml.  Double coating is recommended.  Dry in the dark.  Fix in an 8% hypo solution.

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.

Nicol’s Kallitype I K1a Sensitizer Ferric sodium citrate 20% solution Potassium oxalate 5% solution KIa Developer for Blue-Black Tones Potassium oxalate 20% solution Silver nitrate 1.5% solution Ammonia .880 After mixing the oxalate/silver nitrate solution, add ammonia, drop by drop, until a precipitate forms; then, while stirring constantly, add more ammonia until the brown precipitate dissolves and the solution is clear. K1a Developer for Neutral Black Tones Potassium oxalate 10% solution Silver nitrate 1.5% solution Ammonia .880 Prepare as above. KIa Developer for Sepia Tones Borax 7% solution Silver nitrate 1.5% solution Ammonia .880 Prepare as above. K1b Sensitizer Ferric oxalate 5% solution Ferric tartrate 5% solution Tartaric or oxalic acid 1% solution Prepare as above, using hot water. K1b Developer for Neutral Black Tones Potassium citrate 15% solution Sodium acetate 10% solution Silver nitrate 1.5% solution Ammonia .880 Prepare as per K1a. K1b Developer for Warm Black Tones Potassium citrate 15% solution Potassium oxalate 10% solution Silver nitrate 1.5% solution Ammonia .880 Prepare as above, using hot water. K1 Clearing Bath Potassium citrate 20% solution Ammonia .880 1% solution Immerse in two successive clearing baths for 5 minutes each.  Nicol fixed in the above clearing bath, but Stevens recommends a 5% solution of sodium thiosulfate with 1ml of strong ammonia added.  W. Russel Young III recommends 2 minutes in a 3% citric acid solution.   The print should then be washed thoroughly.  The purpose of the clearing bath is to remove iron compounds.  Many modern workers recommend a fix in sodium thiosulfate as well.  Nicol’s Kallitype II KII Sensitizer Ferric oxalate 75 grains Silver nitrate 30 grains Oxalic acid q.s. Distilled Water 1 ounce Place the ferric oxalate in a bottle with the water, which stand in a saucepan of water, and gradually heat until the ferric oxalate dissolves.  Add not more than 5 to 10 grains oxalic acid to assist solution.  Filter and add the silver nitrate.  Store in the dark. K1I Developer for Black Tones Borax 1 ounce Rochelle salt 3/4 ounce Potassium bichromate 1% sol. 7-9 drams Distilled water 10 ounces K1I Developer for Sepia Tones Rochelle salt 1/2 ounce Potassium bichromate 1% sol. 4-5 drams Distilled water 10 ounces K1I Developer for Purple Tones Borax 1/4 ounce Rochelle salt 1 ounce Potassium bichromate 1% sol. 7-9 drams Distilled water 10 ounces K1I Developer for Maroon Tones Rochelle salt 1 ounce Sodium tungstate 1/2 ounce Distilled water 10 ounces Add potassium bichromate according to desired contrast.  More bichromate gives greater contrast. Nicol’s Kallitype III KIII Sensitizer Ferric oxalate 66 grains Potassium oxalate 13 grains Silver nitrate 13 grains Distilled water 1 ounce If slightly damp, the paper prints out fully in the frame.  Exposure is approximately three times that for KII.  Fix in the following formula. KIII Fix Soda citrate 30 grams Citric acid 5 grams Water 1 liter Nelson C. Hawks’ Formula Sensitizer Ferric oxalate 400 grains Potassium oxalate 100 grains Silver nitrate 100 grains Distilled water 4 ounces Developer Stock Solution Borax 1 ounce Sodium tartrate 1¼ ounce Distilled water (hot) 18 ounces The sensitizer should be filtered before use. Rochelle salts may be substituted for sodium tartrate in the developer.  Dissolve the borax first, and allow the solution to cool somewhat before adding the tartrate.  To use, add ½ dram 2% potassium bichromate to 4 ounces of developer. Avoirdupois to Metric Weight Conversions Ounces Grains Grams 0.03527 15.43 1 16 7000 453.6 1 437.5 28.35   1 0.0648 U.S. Liquid to Metric Measure Ounces Drams Milliliters 1 8 29.57 0.125 1 (60 minims) 3.697 0.03381 0.2705 1 Kallitype Formulae from Dick Stevens Sensitizer Ferric oxalate 20% solution Silver nitrate 10% solution Combine equal quantities for coating.  1.5 ml combined solution is sufficient to coat an 8x10 piece of paper. Developer for Neutral Grey Tones Sodium acetate 100 grams Water 1 quart Tartaric acid 3 grams Sodium dichromate 2% sol. 4-8 ml Developer for Brown Tones Sodium borate (borax) 75 grams Water 1 quart Rochelle salt 37 grams Tartaric acid 3 grams Sodium dichromate 2% sol. 4-8 ml Developer for Sepia Tones Water 1 quart Rochelle salt 50 grams Tartaric acid 3 grams Potassium dichromate 2% sol. 4-8 ml Developer for Blue Tones Rochelle salt 37 grams Water 1 quart Sodium formate 40 grams Tartaric acid 3 grams Potassium dichromate 2% sol. 4-8 ml Developer for Maroon Tones Rochelle salt 37 grams Water 1 quart Sodium tungstate 55 grams Tartaric acid 3 grams Potassium dichromate 2% sol. 4-8 ml KII Developers from W. Russell Young III in Coming into Focus Developer for Black Tones Sodium acetate 150 grams Tartaric acid 1.5 grams Distilled water 1 liter Developer for Brown-Black Tones Borax 50 grams Rochelle salts 40 grams Distilled water 1 liter Developer for Brown Tones Rochelle salts 40 grams Distilled water 1 liter Developer for Black Tones Potassium oxalate 30 grams Distilled water 1 liter Developer for Warm Brown Tones Sodium citrate 200 grams Distilled water 1 liter Sodium citrate is formed by neutralizing a citric acid solution with sodium carbonate (such as Arm & Hammer “super washing soda”). James Thomson’s Formula #3 Sensitizer Citrate of iron and ammonia 25 grains Ferric oxalate 15 grains Chloride of copper 8 grains Oxalate of potassium 35 grains Silver nitrate 15 grains Oxalic acid 15 grains Gum arabic 10 grains Distilled water 1 ounce Developer Stock Solution Silver nitrate 40 grains Citric acid 10 grains Phosphate of soda 2 grains Distilled water 1 ounce Measure out the water, and in half of it dissolve the silver nitrate.  While that is dissolving, weigh the other ingredients into the other half of the water, which should be in a dark-coloured bottle...  Add the chemicals as they are weighed, in the order given, without shaking up the bottle.  When all but the oxalic acid have been added, pour in the silver solution and any undissolved crystals that may be remaining; then add the oxalic acid and without shaking or agitating the bottle, put away in a dark place for 24 hours.  Stir up the sediment at the bottom, then filter, discarding the gritty particles, after which the gum may be added, the solution now being ready for use.  The printing should be carried only so far as to show the deepest shadows. Make a working solution of the developer by mixing 1 dram of developer stock to one ounce of water, adding a grain of oxalic acid to each ounce.  This produces prints of a blue-black hue, whereas a larger quantity of oxalic acid produces a brown-black. When the sensitizer is found to be too strong, reduce by the addition of distilled water.  If not strong enough, add alternately citrate of iron and ammonia, and ferric oxalate a grain at a time, until the image is vigorous enough. Toner for Black Tones Sodium acetate 5 grams Citric acid 5 grams Palladium chloride 5% 1 milliliter Water 1 liter This formula also works with potassium chloroplatinite, though it is much more expensive, giving a nice brown black tone.  Add additional metal salts with each print to be toned. Uranium Toner for Kallitypes Solution A Uranium nitrate 10 grains Glacial acetic acid 1 dram Distilled water 5 ounces Solution B Potassium ferricyanide 10 grains Glacial acetic acid 1 dram Distilled water 5 ounces Mix A and B in equal quantities immediately before toning.  Swab the print front and back with a cotton ball under running water.  Stop the toning action by placing in a bath of water to which a few drops of glacial acetic acid have been added.  Wash for 15 minutes.  This toner has a reducing action, and so is best used on prints that are too dark.  Warning:  highly toxic! To Make Sodium Citrate (20% solution) Citric acid 74.5 grams Sodium carbonate 61.6 grams Water to make 500 ml Dissolve the citric acid in water first.  Then add the carbonate slowly.  The solution will fizz and give off carbon dioxide gas.  Scale up or down as necessary.

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