What is kallitype?

Kallitype is a contact printing process built on the reaction between iron and silver salts. It produces prints with deep shadows and smooth gradations that can be difficult to achieve with modern silver gelatin printing.

The process dates to 1889 and shares much of its process with platinum and palladium printing, at a fraction of the cost.

What draws me to kallitype is the weight of the image. A good kallitype print has a physical presence. The silver sits in the paper fibers, not on top of them. The tones feel embedded, not applied.

The chemistry involves two main components:

• Sensitizer: ferric oxalate, dissolved in water. This is the light-sensitive element. When exposed to UV light, the ferric iron reduces to ferrous iron.

• Silver nitrate: added to the sensitizer solution. The ferrous iron then reduces the silver nitrate to metallic silver, which forms the visible image.

The mixed solution is coated onto paper, dried in the dark, and exposed to UV light through a negative. This is the same contact printing method as cyanotype. But from there, the process demands more attention.

After exposure, the print goes through a series of chemical baths.

Developer brings out the image and the time can vary. A clearing bath is a solution that removes unexposed iron salts that will stain the highlights yellow over time. Then the print is fixed, washed, and dried.

Each of these steps affects the final result. Temperature, timing, paper choice, humidity. Kallitype is responsive to all of these variables, which is what makes it rewarding and part of what can make it unforgiving.

The natural color of an untoned kallitype is a warm brown, but the print is not archivally stable in that state.

Toning replaces the silver image with a more permanent metal, extending the life of the print significantly. I tone my kallitypes in selenium, which shifts the color toward a cool, neutral tone and gives the print archival permanence. Other toning options such as gold, palladium or platinum each produce a different color and character.

How I use it

I use kallitype as both a finished process and as a foundation for layering. A selenium-toned kallitype can serve as the base layer for a cyanotype printed on top, combining the tonal depth of silver with the blue of Prussian blue.

You can see this layering in pieces like Drapes, and kallitype on its own in works like Ceramics and across my still life work.