The kallitype (from the Greek word kalli meaning beautiful) is a member of the iron-based Siderotype (from the Greek root word “sideros” which means “iron”), which was first named, and explained, by Herschel in 1842. Although the Van Dyke and the kallitype processes are quite similar, being iron based, each has its own unique characteristics and idiosyncrasies. In Van Dyke, ferric ammonium citrate is the active UV light-sensitive component in the sensitizer (I like to explain it to my students as the “light-trigger”), whereas in the kallitype, ferric oxalate performs that role… just as it does in platinum and palladium printing. The kallitype sensitizer of ferric oxalate and silver nitrate is coated onto a quality rag paper stock using a hake brush, or glass-rod, and exposed to UV light until a “stage-whisper” is seen. It is then developed in your choice of chemical developer options in order to allow for a variety of color renditions. The print is then distilled water washed, cleared in EDTA (if you are using a borax / sodium borate developer), toned in your choice of toner, fixed with a simple sodium thiosulfate bath, and washed. The kallitype is a close cousin to platinum / palladium in its reliance on ferric oxalate and a metallic salt (platinum chloroplatinite or palladium chloride) to make an image. Many artists consider the kallitype to be the equal of Pt / Pd and there are some knowledgeable folk who still have difficulty distinguishing between the two when the color and image tonality are made to look alike. This was a major selling point of the process when it was first offered to the public. The problem… they were not even in the same parade when it came to permanence.
By 1842, the techniques that would evolve into the kallitype and Brownprint / Sepiaprint / Van Dyke processes, based on the work of Sir John Herschel’s Argentotype, Chrysotype, and Cyanotype techniques, had chemically evolved into printmaking options for photographic image makers. Although Herschel had accurately described how the kallitype process would eventually work, it was not developed and patented until 1889 by Dr. W. W. J. Nicol.