Salt printing is the oldest method for contact printing photographs on paper.
The paper, coated with sodium chloride (salt) solution combined with silver nitrate, is UV sensitive which means the print is made by exposing it to the sun. This process, developed by William Henry Fox Talbot, a British chemist, during the 1830’s, is a positive/negative process he called Calotype (beautiful picture in Greek).
If you are interested in giving it a go, there are two basic ways to utilize this technique:
1. You can get the ingredients and mix the silver and salt solutions yourself (meaning, dissolve the correct amounts of salt and silver nitrate in distilled water) or get a pre-mixed kit.
Both are great ways to begin your experiments; you can choose and follow one of the many salted paper recipes available online but if you’d rather start with a pre-mixed kit and want to save a buck, at Bostick & Sullivan they offer a reasonably priced Salted Paper Printing kit.
After my first time printing salted papers, something chose to occupy my lungs for 2 days. In order to minimize contact with the chemicals I strongly recommend that you choose the Bostick & Sullivan kit, especially if you don’t have a proper area (i.e. some sort of darkroom / laboratory) in your home for working with toxic chemicals and assuming you love the people who share your home with you.
Working with the kit still requires you to take all the safety measures needed but at least you steer clear of mixing the solutions.
The following assumes you are using the Bostick & Sullivan kit but you can still follow these steps even if you are using any other kit or mixing your own solutions.
What you need:
• Chemicals: ammonium chloride, sodium citrate, silver nitrate or Bostick & Sullivan Salted Paper Printing kit.
• Distilled water ($1.19 per gallon).
• Inexpensive brushes such as Gesso brushes ($0.99 – $5.99).
• Uncoated acid-free papers. Most papers will work just fine however papers that are more porous will require more solution and possibly more exposure time. So be creative and experiment with different papers. In order to save $$ start with papers you already have at home. Also try the low-priced printmaking papers (cut them to size by tearing to keep the rough edges) and watercolor paper pads. ($ inexpensive)
• A piece of cardboard, a sheet of glass (you can use glass from an old frame, just make sure it is not UV coated), binder clips, artist tape and removable clear tape. (These items are going to replace the quite expensive printing frame.)
• Paper negatives. You can use your standard negative but since salt printing is a contact printing technique, your final print can only be the same size as your negative. Paper negatives can be any size you make them. Making paper negatives is an easy process and you don’t even need to be a film shooter to make one (see Making paper negatives) .
• 2 shot glasses. Label one of them Salt and the other one Silver. ($ 0 you already have them at home)
• 2 trays (feel free to use aluminum foil baking trays) ($1.49)
• Fixer (included in the kit or dissolve sodium thiosulfate with distilled water)
• The sun (free!)
• Gold toner
• Potassium Dichromate solution for contrast (included in the kit)
Making paper negatives:
Since I suggest using paper negatives for this process here is a quick explanation of how you can easily create them.
There are basically 3 methods of making a paper negative:
1. Place a piece of photographic paper in a pinhole camera and expose it. You will need to develop the paper negative in a darkroom.
2. In the darkroom, place your negative in the enlarger and project your image onto a photographic paper (RC paper will be easier to work with but fiber paper will work as well). Next, develop and fix your photo as usual. When its completely dry contact print it under the enlarger’s light onto another photographic paper, develop and fix as usual. And since you contact printed from a positive photo, you now have created a paper negative.
3. This is the easiest way of making a paper negative and it is done on your PC.
Simply open your chosen photo (preferably a black & white photo\) in your photo editor and convert it to a negative image (In Photoshop: Image /Adjustments/invert in Paintshop Pro: Image/negative image) and print a mirror image of your negative image at any size you wish on standard printer paper. You now have a paper negative.
Coating the paper:
1. (It is a good idea to do the following two steps on the night before you are going to do the actual printing.) Cover your work area with old newspapers. Use the dropper to squeeze the recommended drop count of the salted paper sensitizer into the shot glass and pour it onto the center of the paper you are printing on. Wet your brush with distilled water and use it to spread the solution evenly until it has been absorbed by the paper. If you are adding the optional Potassium Dichromate solution for contrast you should add a drop or two to the salted paper solution before applying it to the paper.
Let the paper completely dry.
2. (It is recommended that you use rubber gloves, eye protection and open all windows before the next step.) Cover your dry paper with the recommended amount of the Silver Nitrate Solution, let the paper completely dry and store it in an area that does not receive any sun light.
Exposing to the sun:
3. (Some people like to use some sort of UV printers but I think it is quite a shame to eliminate the sun which is one of the warmest elements of the process)
Place the paper on a piece of a cardboard and secure it with artist tape so it doesn’t move during exposure. Position the paper negative face down on top of the coated paper and tape it down with a clear removable tape. Place a sheet of glass on top to hold everything tightly together and fasten the glass to the cardboard with binder clips.
4. Set the negative/paper sandwich in the sun. Exposure time will vary according to the strength of the sun, the type of paper, the position of the paper/negative combo (it will take longer if you lay it flat) etc. You can carefully remove the clear tape at one corner and lift the negative to inspect the progress. With experience you will be able to better judge how much exposure time is needed but generally speaking it is better to “overexpose” in the sun as the print will turn lighter in the fixer.
Washing and fixing
5. Carefully remove the print and place it in a tray of water. Agitate the tray and replace the water until the milky residue is gone and the water stays clear.
(If you decide to tone your print you can do it before fixing or after the final wash when the print is still wet) Now transfer your print to the tray with the fixing solution. Agitate the tray and leave the print in the fixer for a few minutes. Replace the print back in the washer tray, set a slow stream of running water and wash the print for about 20 minutes.
And finally hang the print or place it on paper towels until entirely dry.