The Cyanotype is one of several pre-silver gelatin contact printing processes utilizing light sensitive salts to create an image. The process was developed by Sir John Herschel (1842) who discovered an iron salt conversion to metalic iron when exposed to ultra-violet light. This is the same chemical conversion seen in Kallitypes and VanDyke browns.
An emulsion of iron salt and potassium ferricyanide is brushed onto paper, allowed to dry, then placed in a contact printing frame with a negative before exposure to natural sunlight. The resulting image is then developed in a water bath to produce the rich prussian blue tones. Other colors can be achieved with bleaching, toning and altering chemical ratios within the emulsion.
Most of these images are reinterpretations of original silver gelatin prints. They were scanned to digital, then printed as negatives on clear acetate. The final images were contact printed using the cyanotype process on handmade paper, a cotton/abaca blend with an external gelatin sizing. Some are mounted and framed with the brush marks showing; some are matted to hide the over-brushing. Consequently, each has a different aesthetic feel. You can also use the cyanotype process to make pictograms, utilizing opaque objects rather than clear acetate negatives.