The images in the galleries below are calotypes which are negatives on paper made using nineteenth century variants of the same underlying chemical process. Although the term calotype refers to a specific process discovered by Sir William Henry Fox Talbot, I use the term for all the negatives I make to distinguish them from the modern usage of the term “paper negatives” which is now generally understood to mean exposing factory-made gelatin-silver photographic paper in a camera.
The calotype process involves coating paper with a salt solution, typically potassium iodide, followed by treating the paper with silver nitrate to form silver iodide in the paper fibres. This primrose-yellow alkali halide is light sensitive. Beyond that, what distinguishes the different variants of the calotype process are the order in which the chemicals are applied, the use of the paper either wet or dry, the use of other additives (principally organics like whey, isinglass or gelatin) and the use of wax either pre- or post-development.
The main process I use is Pélegry’s process. In 1879 Arsène Pélegry published La photographie des Peintres, des Voyageurs et des Touristes in which he described what is probably the ultimate version of the process, building upon all that went before.
The Pélegry process is amongst the most complex of the paper negative processes. It involves the making of whey from milk which is then mixed with potassium iodide and a little potassium bromide. The sheets of paper are soaked in this and dried. Then, in one continuous process under red light only, the dry sheets of iodised paper are treated to five baths: first silver nitrate, next a pure water bath to remove the excess silver, then salt water to remove all the remaining silver nitrate, another wash and finally they are soaked in a preservative solution of dextrin and tannin before being hung to dry.
After the paper is exposed in the camera all of the calotype processes share a similar development method. The developer is gallic acid (originally extracted from gall nuts) with a drop of aceto-nitrate (a mixture of glacial acetic acid and silver nitrate). The paper negative is then fixed in sodium thiosulphate (hypo). The biggest problem encountered when trying to make calotypes has always been the choice of paper. I settled on handmade paper from Ruscombe Paper Mill in France. The mill was founded in England in 1989 by master papermaker Chris Bingham who moved the business to France in 1995 and ran it until his retirement in 2015. The mill continues production under Chris’s French management team. I use their 100 percent linen paper called Chateau Vellum and had them make me a batch at 70 gsm, a lighter weight than their stock offering. They have since introduced a new 100 percent cotton paper specifically for calotypes, called Timothy 2.0 Calotype, which I am currently testing.
It takes about nine hours to produce 40 sheets of 8”x10” Pélegry paper ready for use. Each sheet costs about €10 to make, currently about 50 percent more expensive than cut sheet film of the same size. Developing each image takes up to three and a half hours. Each negatives sits between 1 to 2 hours in the developer, requires 30 minutes for the fixing stage and a final one-hour wash.
The cameras I use for my work are View cameras; both production (Chamonix 8x10”) and some I have made myself (10x12”, 16x20”) using film-holders in which I sandwich the calotype paper between two sheets of glass.