Colorants

The colorant purple ( dibromoindigo ) and its coloring on a piece of fabric

The chromaticity diagram according to CIE

Colorant is the generic term for all color- giving substances. Inorganic and organic colorants are differentiated according to their chemical composition .

A further distinction can be made in both groups

according to solubility: in pigments and dyes ,
according to the origin: in natural and synthetic colorants,
according to the color: in white, colored, black, effect and luminous colorants and
from a chemical point of view in z. B. elements, oxides, sulfides, chromates, polycyclic, ionic and nonionic colorants.

Classification according to solubility

Inorganic colorants are almost always insoluble and classified as pigments. Organic colorants are available in insoluble (pigments) and soluble form (dyes), the distinction being based on the respective application medium. Some substances can be present as pigment or dye, depending on the medium or chemical group. For example, real indigo is a pigment used to dye jeans on the “dyed product”, as it is insoluble in the cotton fiber and the superficial layer leads to poor rub resistance. In order to dye with indigo, it is vetted . During the vatting process, the indigo is reduced to a soluble " leuco form " and in this state it is soluble in water, making it a dye.

Pigments

Pigments are insoluble in the application medium and are preferably used for emulsion paints , varnishes , plastics , printing inks and artist paints . Inorganic white pigments, such as titanium dioxide , which is preferred today, are used as fillers in papermaking . Highly fast pigments are preferred in order to prevent migration . Not all pigments are completely stable to migration in every colored system. Because they are present as particles, pigments usually have a higher level of fastness than dyes.

Dyes

Dyes are soluble in the application medium, ie in water or organic solvents. The use of the solvents used is determined by the application and the substrates . Typical applications are the coloring of textiles or textile fibers, used as coloring substances in writing utensils and inkjet inks or for the simpler coloring of paper and plastics.

Classification according to origin

Colorants are divided according to their origin or the way they are made.

Synthetic colorants are made using methods of chemistry, for commercial quantities industrially.
Natural colorants are obtained directly from plants, parts of animals, soil or rocks. These include the inorganic white minerals , colored earth pigments , natural mineral pigments and the coloring organic substances such as saffron , indigo or the real purple .

Special colorants

Special colorants are colorants with special physical properties that change their hue under the influence of physical and chemical parameters.

Temperature dependent: colorants with thermochromism

UV light: fluorescent colors

Dyes reacting under the influence of light: photochromic dyes

Indicator colors : are influenced by acid-base reactions or redox processes and help to identify chemical substance classes

Pressure sensitive colorants

Coloring additives in pyrotechnics are mostly based on the spectral lines of the elements, see flare

literature

Ingo Klöckl: Chemistry of colorants in painting . de Gruyter, Berlin 2015, ISBN 978-3-11-037453-7 .
Hermann Kühn: Color, colorants: Pigments and binders in painting . In: Real Lexicon on German Art History . Vol. 7, 1974, Col. 1-54.
Emil (Ernst) Ploß: A book of old colors. Technology of textile colors in the Middle Ages with an outlook on solid colors. Heidelberg and Berlin 1962; Reprint Munich 1967; 6th edition, with two preceding articles on the history of the colors red and blue by Margarete Bruns, Munich 1989, ISBN 978-3-89164-060-9 .
Heinz Roosen-Runge: Color, coloring agent of the occidental medieval illumination . In: Real Lexicon on German Art History . Vol. 6, 1974, col. 1463-1492.
Kurt Wehlte : Materials and techniques of painting . Otto Maier Verlag, Ravensburg 1967, ISBN 3-473-48359-1 (earlier: ISBN 3-473-61157-3 ).

Web links

Individual evidence

↑ DIN 55943 . In: German Institute for Standardization e. V. (Ed.): Colorants 1 . 7th edition. DIN-Taschenbuch 49.Berlin, Vienna, Zurich 2012, ISBN 978-3-410-23202-5 , pp. 509 .
↑ DIN 53160-1 . In: German Institute for Standardization e. V. (Ed.): Colorants 1 . 7th edition. DIN-Taschenbuch 49.Berlin, Vienna, Zurich 2012, ISBN 978-3-410-23202-5 , pp. 143 .
↑ ^a ^b DIN 55944 . In: German Institute for Standardization e. V. (Ed.): Colorants 1 . 7th edition. DIN-Taschenbuch 49.Berlin, Vienna, Zurich 2012, ISBN 978-3-410-23202-5 , pp. 524-525 .

[1] DIN 55943 . In: German Institute for Standardization e. V. (Ed.): Colorants 1 . 7th edition. DIN-Taschenbuch 49.Berlin, Vienna, Zurich 2012, ISBN 978-3-410-23202-5 , pp. 509 .

[2] DIN 53160-1 . In: German Institute for Standardization e. V. (Ed.): Colorants 1 . 7th edition. DIN-Taschenbuch 49.Berlin, Vienna, Zurich 2012, ISBN 978-3-410-23202-5 , pp. 143 .

[:0-3] DIN 55944 . In: German Institute for Standardization e. V. (Ed.): Colorants 1 . 7th edition. DIN-Taschenbuch 49.Berlin, Vienna, Zurich 2012, ISBN 978-3-410-23202-5 , pp. 524-525 .