Cyanotype

Cyanotype is a photographic copying process using light-sensitive iron salts to produce a distinctive blue image. Paper or another suitable absorbent support is coated with a light-sensitive solution. An object or a negative is placed against the support before exposure to ultraviolet light. Rinsing in water follows exposure as part of making the print.

Photograms and photographic prints

When a plant is placed directly on the paper, an image can be made without a camera. This is called a photogram. When a photographic negative is used, the print reproduces its subject. Not every cyanotype is therefore an impression of a plant, although botanical images are familiar examples. The process has also been used to copy architectural and engineering drawings, associated with the term blueprint.

What should be examined?

A blue image alone does not establish cyanotype technique or age. Examine the entire sheet, image surface, inscriptions and documented history. As a practical example, photograph both sides of a loose botanical illustration before separating it from an album. Record the pages and text associated with it.

Rinsing during manufacture is not advice to wash an old photograph. Seek specialist guidance for damage or unidentified photographic materials. See also preserving old photographs.

Next step

Browse prints and graphic art for current works. When planning estate clearance with OBA, identify albums and loose photographs as a separate group before sorting or a possible sale.