Salt printing is more than just a photographic technique – it is a true art form that captures the essence of emulsion-based photography while offering a unique and timeless aesthetic. Here in RadLab Studio we are passionate about preserving this historic process and sharing it with print enthusiasts like you. We’ve cranked up the volume with dedicated lab for alternative processes, custom digital negative profiles, delivering exceptional tonal range, great contrast and sometimes unexpected results.
What is Salt Printing?
Photo: Ivelin Penchev
Salt printing is a photographic process that dates back to the early 19th century. Invented by William Henry Fox Talbot, a pioneer in the field of photography, this technique revolutionized image-making at the time. Salt printing is a complex process and involves creating a photographic print by coating paper with a light-sensitive solution containing salt and silver nitrate, resulting in stunningly beautiful images with specific charisma.
The Chemistry Behind Salt Printing
At Radlab Studio, we believe that understanding the chemistry behind every process enhances the appreciation of it as an art form. The key to salt printing lies in the reaction between salt and silver nitrate. When the salt and silver nitrate combine, they form light-sensitive silver chloride, which is embedded in the fibers of the paper. This light-sensitive material captures the image when exposed to ultraviolet (UV) light. The salt printing process embraces its artistic unpredictability, with numerous variables at play, including paper pH, air temperature, humidity, and preparation methods. At RadLab Studio, we prioritize safety and provide protective wear to ensure your well-being as we navigate the captivating realm of chemical substances.
Step-by-Step Salt Printing Guidance
While the salt printing process entails various variables, making it unpredictable, we have developed and refined a method that consistently delivers great results, providing us with a reliable and effective approach to create stunning prints. Here’s a breakdown of how we are making this process using contact printing with UV light:
Step 1: Salting the paper
To initiate the salt printing process, we immerse the paper in a solution containing either sodium chloride (NaCl) or ammonium chloride NH4Cl. This step allows the salt to penetrate the paper fibers, preparing them for the subsequent reaction with silver in the next phase. By effectively infusing the paper with salt, we create the foundation for the chemical interaction that produces the distinctive characteristics of a salt print. The way the print turns out in terms of contrast, tonal range, and color toning can also be influenced by this step. We use a concentration of 20 grams of NH4Cl per liter of water and soak the paper in it for about 3 to 5 minutes. After that, we let the paper air dry.
Step 2: Sensitizes and Paper coating
After the salted paper has dried, it’s time to make it light sensitive by applying a solution of silver nitrate. It’s important to conduct this step in low light conditions, avoiding overhead neon lights or direct sunlight. To begin, prepare the desired concentration of the silver nitrate solution with caution.
There are two formulas we use for sensitizer:
The first formula is a 10% silver nitrate (AgNO3) solution with 5% citric acid added. It is recommended for addressing highlight problems or when immediate printing is not planned. The citric acid acts as a preservative and lowers the pH. To make this formula, mix 10 grams of AgNO3 with 50 ml of warm distilled water. Separately, mix 5 grams of citric acid with the remaining 50 ml of warm distilled water. Stir gently with a non-metallic stirrer and use a dark glass container for storage.
The second formula is a traditional 10% AgNO3 solution without citric acid. It involves adding 10 grams of AgNO3 to 100 ml of warmed distilled water. This formula can be adjusted to different concentrations based on preference, with some authors prefer opting for a 6% concentration and double coating. Silver nitrate has a long shelf life.
Coating the salted paper with the sensitizer involves using a synthetic brush or the floating method. Using a Synthetic Flat Brush provides consistent coating and lessens damage to wet paper fibers. Use distilled water for washing and always clean the brush after each coating. Instead of dipping the brush into a container with AgNO3 solution, count individual drops in a shot glass to avoid contamination. 3ml of the solution is enough for coating 20×30 cm sheet of salted paper. If dipping is necessary, seal the metal ferrule of the brush to prevent contact with the sensitizer. In the traditional floating method, use a tray about the same size as the paper and float the paper on silver nitrate solution. Mark the back of the paper and avoid getting emulsion on the back of the paper. For better results coat in subdued light and consider multiple low concentration.
Step 3: Drying the Coated Paper
The coated paper is carefully dried in a darkroom or low-light environment. It is essential to ensure that the paper is completely dry before moving on to the next step.
Step 4: Contact Printing
A digital negative is placed in contact with the dried, coated paper. This sandwich is then exposed to UV light source like sunlight for about 15 to 60 min depending on the season, where on Earth you are situated and the time of the day. The UV light causes a chemical reaction, resulting in the creation of a latent image. Here in RadLab Studio we are using a UV lamp that gives us constant light density and great results for about 19 minutes.
Step 5: Salt Bath and washing
The purpose of this slightly acidic salt bath is to precipitate excess silver by forming silver chloride. Without this step, problems may arise with toning and gold adhesion. The bath is prepared by adding 10gr citric acid and 30gr NaCl salt in 1 liter distilled water. The print should be immersed in this bath for 5 minutes, agitated slowly. Afterward, the print is moved to fresh water trays for rinsing, repeated two to three times for about 5 min each.
Step 6: Optional Toning Bath
Photo: Natalia Simeonova
In the salt printing process, there are primarily two toning options: gold toning and selenium toning.
Gold Toning: Gold toning involves immersing the salt print in a gold chloride solution. This process imparts a warm, golden hue to the print, enhancing its overall tonal range and adding a pleasing aesthetic. Gold toning can improve the permanence and archival qualities of the print by reducing its susceptibility to fading over time.
Selenium Toning: Selenium toning is another common technique used in salt printing. The print is treated with a dilute solution of sodium or potassium selenite. Selenium toning can significantly change the appearance of the print, resulting in a wide range of brown tones. This process not only alters the color but also improves the print’s archival stability, increasing its resistance to fading and enhancing its longevity.
Step 7: Fixing and final wash
For this step we are using HYPO fixer, that contains Sodium thiosulphate. Soak the print in a fixing tray for 3 minutes and then gently wash it in a tray fresh tap water. Change the water 3 times every 5 minutes.
Step 8: Drying and Finishing
Photo: Vladislav Lepoev
The final step involves carefully drying the print and then preserving it for generations to come.
Whether you’re an experienced photographer or a curious beginner, we are here to guide you through the salt printing process. Unleash your creativity and immerse yourself in the art of salt printing at RadLab Studio. Contact us today and embark on a journey into the fascinating world of alternative photographic processes.