Salted Paper Formulae

by Ed Buffaloe

Salted paper is perhaps the most basic of the historical or alternative processes, giving a color much like Vandyke Brown but with no worries about residual iron compounds, a somewhat longer tonal scale, and a very different gradation. The process combines a salt with silver nitrate to form a halide of silver (usually silver chloride), but since silver halides are insoluble in water it is necessary to make them form within the paper itself by coating first with the salt solution and then with the silver sensitizer.  The paper is dried between steps.

Sizing paper with gelatin, arrowroot, casein or cornstarch is recommended to keep the solutions from sinking beneath the surface, which causes the print to lose contrast.  Often gelatin is combined with the salt, but sometimes the paper is sized first and then salted.  The Albumen and Salted Paper Book, by James M. Reilly, states that typically the silver nitrate solution should be about 4 times as strong as the salt solution--so, if a 3% salt solution is used, a 12% silver nitrate solution is required (though none of the formulae below reflect this ratio).

Paper may be coated by immersion in the solutions, or by brush.  Since the salt is relatively cheap, I find it best to salt and size paper by immersion (which helps prevent paper curling because both sides are coated), but I generally use a brush or rod for coating the sensitizer.  If you coat the salt solution by brush, be sure to use a separate brush for salt and sensitizer.  Do not use a brush with a metal ferrule.  If you use a rod, a drop or two of 5% Tween-20 will help produce a more even coat with some papers.  Wear gloves when handling the silver nitrate solution.

Salted paper is particularly sensitive to minute impurities, so it is necessary to use clean utensils and carefully guard against contaminating solutions.  You may find it necessary to use distilled water for the initial wash.  Toning is usually accomplished before fixing, but may also be done afterward.  Gold is the traditional toner, but I find I prefer the color produced by a highly dilute solution of Kodak Rapid Selenium Toner (3 ml in 1 liter of water), used after the fix for 1 minute only--it produces a rich, chocolate brown color.

Salted paper is usually fixed in a 10% solution of hypo (100 grams of sodium thiosulfate in 1 liter of water) for 10 minutes.  Two fixes are recommended for optimal print permanence.

Salted paper requires a very high-contrast negative with a density range in the vicinity of 2.0 or higher.

Typical procedure:

1. Coat paper with salt solution (usually with size added), and dry.
2. Coat paper with silver solution, and dry thoroughly in the dark.
3. Expose paper by contact printing with a negative under UV or sunlight.
4. Wash in running water for 2 minutes.  (I use distilled water with 2 minutes continuous agitation, followed by a running water wash.)
5. Tone, if desired.
6. Fix for 10 minutes.
7. Wash for at least 40 minutes.  The wash may be accelerated by the use of a wash aid such as Kodak Hypo Clearing Agent or a 20% solution of sodium sulfite.

from The Photo Miniature #69 Salt Solution Sodium chloride 60 grains Citric acid 120 grains Distilled water 7 ounces Soft gelatine 1/2 ounce Sensitizer Silver nitrate 150 grains Distilled water 4 ounces The salt and acid are first dissolved in the water, and then the gelatine is added, and the whole stirred and gradually heated up to about 40°C (105° F) until complete solution has taken place.  The solution must be strained or filtered through two thicknesses of muslin to free it from small insoluble particles of gelatine. from Coming into Focus Salt Solution Ammonium chloride 10 grams Potassium citrate 10 grams Distilled water to make 500 ml Sensitizer Silver nitrate 12 grams Distilled water to make 100 ml This source recommends sizing independently of salting, but I have combined the two here. from Historic Photographic Processes Salt Solution Water 250 ml Gelatine 2 grams Sodium citrate 5 grams Ammonium chloride 5 grams Sensitizer Distilled water 90 ml Silver nitrate 12 grams Distilled water to make 100 ml If arrowroot-sized paper is used, the sensitizer should contain 4-5% citric acid. from Encyclopedia of Photography Salt Solution Gelatine 100 grains Chrome alum 4 grains Ammonium chloride 50 grains Water to make 10 ounces Sensitizer Silver nitrate 600 grains Citric acid 300 grains Distilled water to make 10 ounces Soak gelatine 30 minutes in 8 ounces of cold water, and dissolve the chrome alum in 2 ounces.  Heat the gelatine mixture in a water bath and stir in the ammonium chloride.  Strain the gelatine solution through fine muslin and gradually add the chrome alum solution.  Store in hot water to keep the solution fluid for coating.  Sponge the salt solution on as quickly and evenly as possible, and go over with a squeezed sponge to remove excess solution. Namias’ Formula Salt Solution Gelatin 25 grams Citric acid 5 grams Ammonia 6 ml Zinc chloride crystals 6 grams Water 1 liter Soak the gelatin in half the water and dissolve with heat up to about 105° F (40°C ); dissolve the acid in the remainder of the water, add the ammonia, then the chloride.  Mix the two solutions and filter.  Tartaric acid may be substituted for citric to obtain darker brown tones. Sensitizer Silver nitrate 12 grams Citric acid 5 grams Glycerin 5 ml Water 100 ml Greater contrast may be obtained by adding small amounts of a 5% solution of potassium bichromate. 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 from Spirits of Salts Salt Solution Sodium chloride (or ammonium) 20 grams Cold tap water 1 liter Sensitizer Solution 1   Distilled water 50 ml Silver nitrate 12 grams Solution 2   Distilled water 50 ml Citric acid 6 grams Combine solutions 1 and 2. Salt Solution with Gelatin Sodium chloride 6 grams Gelatin 2 grams Water to make 300 ml Place gelatine in 100 ml water and let soak for 15 minutes.  Add 200 ml water at 45° C and stir until dissolved.  Then add the salt. from The Keepers of Light Gelatin/Salt Solution Water 280 ml Gelatin 2 grams Sodium citrate 6 grams Ammonium chloride 6 grams Soak gelatin in 100 ml room temperature water for 10 minutes, then add 180 ml water at 43° C (100° F) and dissolve rest of chemicals. Starch/Salt Solution Water 280 ml Argo cornstarch 5 grams Sodium citrate 6 grams Ammonium chloride 6 grams Dissolve starch in 80 ml room temperature water, then add 200 ml boiling water.  Boil 3 minutes and remove from heat.  Add the other chemicals while stirring. Sensitizer Distilled water at 38° C (100° F) 30 ml Silver nitrate 4 grams from Photographic Facts and Formulas Arrowroot/Salt Solution Arrowroot 20 grams Water 750 ml Rub the arrowroot into a cream with a small amount of water.  Boil the remainder of the water and add the arrowroot cream slowly with constant stirring.  Stir until a translucent liquid is formed.  The quantity of arrowroot may be increased to 30 grams for better surface brilliance.  Then add: Ammonium chloride 14 grams Sodium carbonate (crystals) 23 grams Citric acid 7 grams Water 250 ml Boil the salt solution for 5 minutes to eliminate carbon dioxide and add very slowly to the arrowroot liquid with constant stirring.  Use a container twice the size of the solution you are mixing so it does not boil over.  Strain the solution through fine muslin while hot. Gelatin/Salt Solution Gelatin 4.5 grams Ammonium chloride 18 grams Sodium citrate 21.5 grams Salt 7 grams Water 1 liter Sensitizer Silver nitrate 73 grams Citric acid 52 grams Water 500 ml Modified Caseine Formula from Photographic Facts & Formulas Salt Solution Ammonium chloride 4 grams Sodium citrate 40 grams Water to make 500 ml Casein Solution Casein 40 grams Ammonia 50 ml Water to make 500 ml The casein solution can be made from 40 grams of washed low fat cottage cheese curds, with the same amount of ammonia and water.  Either way, you must warm the solution until the curds dissolve.  Mix the salt and casein solutions separately, then combine them while stirring continuously.   Strain the combined solution through a layer of muslin and immerse paper for two minutes.  Hang to dry.  The solution will only keep for a day or two, so size all the paper you will need ASAP. Sensitizer Silver nitrate 14 grams Citric acid 10 grams Water to make 100 ml This was originally a single-solution wherein 70 grams of silver nitrate were added, but it seems to work better as a two solution formula.

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