Cyanotype is an old monochrome photographic printing process that gives a cyan-blue print. A photograph of a sign in grayscale The same photograph in black and white Monochrome comes from the two Greek words mono (μωνο, meaning one), and chroma (χρωμα, meaning surface or the color of the skin). A monochromatic object has a single color. ... This page list various photographic processes. ... Cyan (from Greek κυανοs, meaning blue) may be used as the name of any of a number of a range of colors in the blue/green part of the spectrum. ...

The English scientist and astronomer Sir John Herschel discovered this procedure in 1842. Though Herschel is perhaps the inventor of the cyanotype process, it was Anna Atkins, a British scientist, who brought the process into the realm of photography. She created a limited series of cyanotype books that documented ferns and other plant life. By using this process, Anna Atkins is regarded as the first woman photographer. John Herschel Sir John Frederick William Herschel (7 March 1792 – 11 May 1871) was an English mathematician and astronomer. ... 1842 was a common year starting on Saturday (see link for calendar). ... A cyanotype photogram made by Atkins which was part of her 1843 book, British Algae: Cyanotype Impressions Anna Atkins (née Children) (1799-1871), a British botanist, is credited with creating the first ever book of exclusively photographic images, titled British Algae: Cyanotype Impressions, a collection of cyanotype photograms of...

The process uses two chemicals:

• Ammonium iron(III) citrate
• Potassium ferricyanide

They result in a photo-sensitive solution when dissolved in water, which is used to coat a material (usually paper). A positive image can be produced by exposing it to a source of ultraviolet light (such as sunlight) with a negative. The UV light reduces the iron(III) to iron(II). This is followed by a complex reaction of the iron(II) complex with ferricyanide. The result is an insoluble, blue dye (ferric ferrocyanide) known as Prussian blue. Ammonium ferric citrate (Cas No:1185-57-5, Einecs No. ... Potassium ferricyanide (K3[Fe(CN)6]) also known as red prussiate, Prussian red or potassium hexacyanoferrate(III), is a coordination compound that is stable at room temperature and pressure and forms ruby red crystals and powder. ... UV redirects here. ... The most fundamental reactions in chemistry are the redox processes. ... A sample of Prussian blue Prussian blue (German: Preußisch Blau, Berliner Blau) is a dark blue pigment used in paints and formerly in blueprints. ...

The developing of the picture takes place by flushing it with flowing water. The water-soluble iron(III) salts are washed away, while the non-water-soluble Prussian blue remains in the paper. This is what gives the picture its typical blue color. The process was popular in engineering circles well into the 20th century. The simple and low-cost process enabled them to produce large-scale copies of their work, referred to as blueprints. A piece of photographic film that has been exposed to light in a controlled manner must be developed before it can be used. ... Modern blueprint of the French galleon La Belle. ...

The Process

In a typical procedure, equal volumes of an 8% (w/v) solution of potassium ferricyanide and a 20% solution of ferric ammonium citrate are mixed. This mildly photosensitive solution is then applied to a receptive surface (such as paper) and allowed to dry in a dark place. Cyanotypes can be printed on any surface capable of soaking up the iron solution. Although watercolor paper is a preferred medium, cotton, wool and even gelatin sizing on nonporous surfaces have been used. In biology percentage solutions are often preferred to molar ones. ... Photosensitivity is the amount to which an object reacts upon receiving photons of light. ... Watercolor is a painting technique making use of water-soluble pigments that are either transparent or opaque and are formulated with gum to bond the pigment to the paper. ... Cotton ready for harvest. ... Long and short hair wool at the South Central Family Farm Research Center in Boonesville, Arizona Wool is the fiber derived from the fur of animals of the Caprinae family, principally sheep, but the hair of certain species of other mammals such as goats, alpacas, llamas and rabbits may also... Gelatin (also gelatine, from French gélatine) is a translucent brittle solid substance, colorless or slightly yellow, nearly tasteless and odorless. ... This article or section does not cite any references or sources. ... A porous medium or a porous material is a solid (often called frame or matrix) permeated by an interconnected network of pores (voids) filled with a fluid (liquid or gas). ...

Upon exposure to ultraviolet light (such as that in sunlight), the iron in the exposed areas will reduce, turning the paper a steel-grey-blue color. The extent of color change is dependent on the amount of UV light, but acceptable results are usually obtained after 10-20 minute exposures on a bright, sunny day. Prints can be made with large format negatives and lithography film, or everyday objects can be used to make photograms. Color, positive picture (A) and negative (B), monochrome positive picture (C) and negative (D) In photography, a negative may refer to 3 different things, although they are all related. ... Lithography stone and mirror-image print of a map of Munich. ... A colour photogram of lemons and tomato stems. ...

After exposure, the yellow, unreacted iron solution is rinsed off with running water. Although the blue color darkens upon drying, the effect can be accelerated by soaking the print in a 6% (v/v) solution of 3% (household) hydrogen peroxide. Hydrogen peroxide (H2O2) is a very pale blue liquid which appears colourless in a dilute solution, slightly more viscous than water. ...

Long-term preservation

In contrast to most historical and present-day processes, cyanotype prints do not like basic environments. So it is not a good idea to store or present the print in chemically buffered museum board. This will cause the image to fade. Another unusual characteristic of the cyanotype is its regenerative behaviour: prints that have faded due to prolonged exposure to light can often be significantly restored to their original tone by simply temporarily storing them in a dark environment. Acids and bases: Acid-base reaction pH Self-ionization of water Buffer solutions Systematic naming Acid-base extraction Acidity function Proton affinity Acids: Strong acids Weak acids Superacids Lewis acids Mineral acids Organic acids Bases: Strong bases Weak bases Superbases Lewis bases Organic bases edit In chemistry, a base is...

References

• Atkins, Anna, with text by Lynn J. Schaff. Sun Gardens: Victorian Photograms. New York; Aperture, 1985.
• Blacklow, Laura. (2000) New Dimensions in Photo Processes: a step by step manual. 3rd ed.
• Ware, M. (1999) Cyanotype: the history, science and art of photographic printing in Prussian blue. Science Museum, UK

External links

• An article on toning a digital image in Photoshop.
• Mike Ware's New Cyanotype - a new version of the cyanotype that address some of the classical cyanotypes short comings
• Cyanotypes.com - a free information centre with articles and galleries on the cyanotype process
• The Cyanotype process
• Photoshop action to give a cyanotype look to a digital photo