Salt printing (aka Sun printing) was the original photographic printing process. It dates back to 1830’s where it was invented by the father of Photography Henry Fox Talbot, he worked on perfecting salt prints (and the negative form which he called Calotypes) during the 1830’s and eventually patented his process in 1839.
Salt prints get their name from one of the key ingredients; Salt (Sodium Chloride). During the 19th century salt prints were also referred to as ‘sun prints’ because this is a printing out process, where the negative is “contact” printed with the paper under UV light, most commonly the sun.
Developing couldn’t be simpler just wash the print under water to wash the un-developed silver and fix in hypo.
Because this is a printing out process, you need to contact print, you can’t use an enlarger, therefore you need some big negatives. This means if you don’t shoot Large format film, you should look at making digital negatives.
So how do you do it:
the basic recipe is
- 2% sodium chloride solution
- 12% Silver nitrate solution
First coat the paper with the salt solution and wait till it dries, then under safe light conditions coat the paper with the silver nitrate solution, once this dries you are ready to contact print.
DO NOT put a negative on wet paper you will destroy the neg.
Expose the print to direct sunlight and watch the magic happen, wait till it looks a little over exposed. It will lighten when developing. Develop under running water for a few minutes. fix in hypo for 4 minutes, then using a second hypo bath fix for another 4 min (for archivability), then a final 4 min in hypo clear, and wash in water for up to 40 min depending on the thickness of the paper used.
NOTE: Table salt contains Iodine which will fog the print, use rock salt or kosher salt. You can also use sea water, but you need to boil it first to kill any microbes.