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A French Indienne, a printed or painted textile in the manner of Indian productions, which used mordants to fix the dyes.

A mordant is a substance used to set dyes on fabrics or tissue sections by forming a coordination complex with the dye which then attaches to the fabric or tissue.^[1] It may be used for dyeing fabrics, or for intensifying stains in cell or tissue preparations. The term mordant comes from the Latin word, "mordere", to bite. In the past, it was thought that a mordant helped the dye bite onto the fiber so that it would hold fast during washing. A mordant is often a polyvalent metal ion.^[2] The resulting coordination complex of dye and ion is colloidal and can be either acidic or alkaline.

Common dye mordants[link]

Mordants include tannic acid, alum, urine, chrome alum, sodium chloride, and certain salts of aluminium, chromium, copper, iron, iodine, potassium, sodium, and tin.

Iodine is often referred to as a mordant in Gram stains but is in fact a trapping agent.^[3]

Dyeing methods[link]

Dye rot from iron mordant

The three methods used for mordanting are:

• Pre-mordanting (onchrome): The substrate is treated with the mordant and then dyed.
• Meta-mordanting (metachrome): The mordant is added in the dye bath itself.
• Post-mordanting (afterchrome): The dyed material is treated with a mordant.

The type of mordant used changes the shade obtained after dyeing and also affects the fastness property of the dye. The application of mordant, either pre-, meta- or post-mordant methods, is influenced by:

• The action of the mordant on the substrate: if the mordant and dye methods are harsh (e.g. an acidic mordant with an acidic dye), pre- or post- mordanting limits the potential for damage to the substrate.
• The stability of the mordant and/or dye lake: the formation of a stable dye lake means that the mordant can be added in the dye without risk of losing the dye properties (meta-mordanting).

Dye results can also rely on the mordant chosen as the introduction of the mordant into the dye will have a marked effect on the final color. Each dye can have different reactions to each mordant. For example, cochineal scarlet, or Dutch scarlet as it came to be known, used cochineal along with a tin mordant to create a brilliant orange-hued red.^[4] Residual iron mordant can damage or fade fabric, producing "dye rot".^[5]

The dye lake[link]

The dye lake is an insoluble molecule formed when the complex of dye and mordant are combined, which then attaches to the substrate. Mordants increase the fastness of the dye since the larger molecule is now bonded to the fibre.^[2]

The term "lake" is derived from the term lac, the secretions of the Indian wood insect Laccifer lacca (formerly known as the Coccus lacca). This is the same insect from which shellac is obtained.^[6] The type of mordant used can change the colour of both the dye-plus-mordant solution and influence the shade of the final product.

Wool[link]

Unlike cotton, wool is highly receptive toward mordants. Due to its amphoteric nature wool can absorb acids and bases equally effectively. When wool is treated with a metallic salt it hydrolyses the salt into an acidic and basic component. The basic component is absorbed at –COOH group and the acidic component is removed during washing. Wool also has a tendency to absorb fine precipitates from solutions; these cling to the surface of fibres and dye particles attached to these contaminants result in poor rubbing fastness.

Silk[link]

Like wool, silk is also amphoteric and can absorb both acids as well as bases. However, wool has thio groups (-SH) from the cystine amino acid, which act as reducing agent and can reduce hexavalent chromium of potassium dichromate to trivalent form. The trivalent chromium forms the complex with the fibre and dye. Therefore potassium dichromate cannot be used as mordant effectively.

Animal and plant Tissues[link]

In Histology, mordants are indispensable in adhering dyes to tissues for microscopic examination.

Methods for mordant application depend on the desired stain and tissues under study; pre-, meta- and post-mordanting techniques are used as required.

The most commonly used stain used in diagnostic histology of animal tissues is Harris' haematoxylin as part of a haematoxylin and eosin (H&E) stain.

References[link]

v t e Dyeing Techniques Batik Dyeing Kalamkari Katazome Leheria Mordant Reactive dye printing Resist Ring dyeing Rōketsuzome Shibori Tie-dye Tsutsugaki Types of dyes Dyes Natural Acid Reactive Solvent Substantive Sulfur Vat Disperse Traditional textile dyes Black walnut Bloodroot Brazilin Cochineal Cudbear Cutch Dyewoods Fustic Henna Indigo Kermes Logwood Madder Polish cochineal Saffron Turmeric Tyrian purple Weld Woad History Trade and use of saffron Traditional dyes of the Scottish Highlands Craft dyes Dylon Procion Reference Glossary of dyeing terms List of dyes

This biographical article needs additional citations for verification. Please help by adding reliable sources. Contentious material about living persons that is unsourced or poorly sourced must be removed immediately, especially if potentially libelous or harmful. (December 2008)

Han Berger (born June 17, 1950 in Netherlands) is a Dutch football coach^[1] and former football player.

Biography[link]

Han Berger is the youngest head coach ever in the history of professional football in The Netherlands. After suffering a severe knee injury, his playing career ended at the age of 22 and he was appointed youth and assistant coach at his hometown side FC Utrecht. When the then head coach Jan Rab was dismissed in January 1976, Han Berger was appointed head coach of FC Utrecht at the age of 25.

After that he coached the amazing number of 637 games in the Dutch Eredivisie being particularly successful with FC Utrecht and FC Groningen, leading them to a number of spectacular UEFA Cup campaigns. Under his management Cambuur Leeuwarden in 1998 won the 1st division play-offs for promotion to the Eredivisie.

From 1998 till August 2000 Han Berger was in charge of the national youth teams program of the Royal Dutch Football Association (KNVB) and head coach of The Netherlands U/21 and Olympic Team and in 2004 he coached Oita Trinita in the Japanese J1-League who have since been relegated to the J2-League.

The last decade he held the position of director of football at FC Utrecht and De Graafschap in which role he acquired a reputation for implementing successful technical strategies, particularly in the field of youth development.

References[link]

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