The process I use in my images is called the “Cyanotype Process”. It originates from the beginnings of photography and was invented by Sir John Herschel, an astronomer and scientist, in 1842. He was just trying to find a way to copy his notes but the process was used one year later already by Anna Atkins in the first photographically illustrated book ever, a book about ferns.
The process itself was the first successful non-silver photographic printing process and uses iron salts instead of silver which provides a beautiful Prussian Blue colour. The cyanotype process results in permanent images in an elegant assortment of blue values, but can be toned to warmer colours, almost like sepia.
The cyanotype is exposed by ‘contact printing’: a paper (or fabric) of your choice is coated with the iron salt containing liquid (the sensitiser solution), and a negative is then sandwiched onto it and secured. This bundle is then exposed in the sun, and afterwards separated, washed and dried.
This means that there are lots of variables in the process that influence the end product and that no two images will be the same. You will end up with a unique image, printed just like 160 years ago.