A mordant or dye fixative is a substance used to set (i.e. bind) dyes on fabrics. It does this 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. Although mordants are still used, especially by small batch dyers, it has been largely displaced in industry by directs.[2]
A French Indienne, a printed or painted textile in the manner of Indian productions, which used mordants to fix the dyes
The term mordant comes from the Latin 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 polyvalentmetalion, and one example is chromium (III).[3] The resulting coordination complex of dye and ion is colloidal and can be either acidic or alkaline.
Iodine is often referred to as a mordant in Gram stains, but is in fact a trapping agent.[3]
Dyeing methods
Dye rot from iron mordant
The three methods used for mordanting are:
Pre-mordanting (onchrome): The substrate is treated with the mordant and then the dye. The complex between the mordant and dye is formed on the fibre.
Meta-mordanting (metachrome): The mordant is added in the dye bath itself. The process is simpler than pre- or post-mordanting, but is applicable to only a few dyes. Mordant red 19 shown above is applied in this manner
Post-mordanting (afterchrome): The dyed material is treated with a mordant. The complex between the mordant and dye is formed on the fibre.
The type of mordant used affects the shade obtained after dyeing and also affects the fastness property of the dye. The application of mordant, either pre-mordant, meta-mordant or post-mordant methods, is influenced by:
The action of the mordant on the substrate: if the mordant and dye methods are harsh (for example, an acidic mordant with an acidic dye), pre-mordanting or post-mordanting limits the potential for damage to the substrate.
The stability of the mordant or dye lake or both: 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.[5]
Residual iron mordant can damage or fade fabric, producing "dye rot".[6]
Dye lake
The dye lake is an insoluble complex formed upon combining the dye and mordant, which then attaches to the substrate. Mordants increase the fastness of the dye since the higher molecular weight dye is now bonded to the fibre.[3]
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
Unlike cotton, wool is highly receptive toward mordants. Due to its amphoteric nature wool can absorb acids and bases with equal efficiency. 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.
The discovery of Congo red in 1883, followed by many other synthetic azo dyes, heralded the demise of mordant dyes.
Silk
Like wool, silk is also amphoteric and can absorb both acids and bases. However, wool has thio groups (-SH) from the cystineamino 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 effectively as mordant.
^ abcLlewellyn, Bryan D. (May 2005). . Archived from the original on May 20, 2016.
^Von Wagner, Rudolf (1897). Manual of chemical technology. New York: D. Appleton & Co. p. 499.
^Phipps, Elena (2010). Cochineal Red The Art History of a Color, p34. Yale University Press, New Haven and London. ISBN978-0-300-15513-6.
^. Archived from the original on 2012-12-21. Retrieved 2012-01-29.
Further reading
Buchanan, Rita (1999). A Weaver's Garden: Growing Plants for Natural Dyes and Fibers. Courier Corporation. ISBN9780486407128.
Barber, E. J. W. (1991). Prehistoric Textiles: The Development of Cloth in the Neolithic and Bronze Ages with Special Reference to the Aegean. Princeton University Press. ISBN069100224X.
External links
Griffin Dyeworks: Understanding mordants and modifiers
May 26, 2023
mordant, this, article, about, substance, used, dyes, musical, ornament, mordent, other, uses, disambiguation, mordant, fixative, substance, used, bind, dyes, fabrics, does, this, forming, coordination, complex, with, which, then, attaches, fabric, tissue, use. This article is about the substance used to set dyes For the musical ornament see Mordent For other uses see Mordant disambiguation A mordant or dye fixative is a substance used to set i e bind dyes on fabrics It does this 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 Although mordants are still used especially by small batch dyers it has been largely displaced in industry by directs 2 Mordant red 19 is a typical mordant dye Like many mordant dyes it features the azo group RN NR and various sites for chelating to metal cations A French Indienne a printed or painted textile in the manner of Indian productions which used mordants to fix the dyes The term mordant comes from the Latin 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 and one example is chromium III 3 The resulting coordination complex of dye and ion is colloidal and can be either acidic or alkaline Contents 1 Common dye mordants 2 Dyeing methods 2 1 Dye lake 2 2 Wool 2 3 Silk 2 4 Animal and plant tissues 3 References 4 Further reading 5 External linksCommon dye mordants EditMordants include tannic acid oxalic acid 4 alum chrome alum sodium chloride and certain salts of aluminium chromium copper iron iodine potassium sodium tungsten and tin Iodine is often referred to as a mordant in Gram stains but is in fact a trapping agent 3 Dyeing methods Edit Dye rot from iron mordant The three methods used for mordanting are Pre mordanting onchrome The substrate is treated with the mordant and then the dye The complex between the mordant and dye is formed on the fibre Meta mordanting metachrome The mordant is added in the dye bath itself The process is simpler than pre or post mordanting but is applicable to only a few dyes Mordant red 19 shown above is applied in this manner Post mordanting afterchrome The dyed material is treated with a mordant The complex between the mordant and dye is formed on the fibre The type of mordant used affects the shade obtained after dyeing and also affects the fastness property of the dye The application of mordant either pre mordant meta mordant or post mordant methods is influenced by The action of the mordant on the substrate if the mordant and dye methods are harsh for example an acidic mordant with an acidic dye pre mordanting or post mordanting limits the potential for damage to the substrate The stability of the mordant or dye lake or both 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 5 Residual iron mordant can damage or fade fabric producing dye rot 6 Dye lake Edit The dye lake is an insoluble complex formed upon combining the dye and mordant which then attaches to the substrate Mordants increase the fastness of the dye since the higher molecular weight dye is now bonded to the fibre 3 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 Edit Unlike cotton wool is highly receptive toward mordants Due to its amphoteric nature wool can absorb acids and bases with equal efficiency 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 The discovery of Congo red in 1883 followed by many other synthetic azo dyes heralded the demise of mordant dyes Silk Edit Like wool silk is also amphoteric and can absorb both acids and 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 effectively as mordant Animal and plant tissues Edit In histology mordants are indispensable in fixing 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 amp E stain References Edit IUPAC Compendium of Chemical Terminology 2nd ed the Gold Book 1997 Online corrected version 2006 mordant doi 10 1351 goldbook M04029 Hunger Klaus Mischke Peter Rieper Wolfgang Zhang Shufen March 8 2019 Azo Dyes 5 Developing Dyes Ullmann s Encyclopedia of Industrial Chemistry Weinheim Germany Wiley VCH Verlag GmbH amp Co KGaA pp 1 19 doi 10 1002 14356007 o03 o09 pub2 ISBN 9783527306732 OCLC 46878292 a b c Llewellyn Bryan D May 2005 Stain Theory How mordants work Archived from the original on May 20 2016 Von Wagner Rudolf 1897 Manual of chemical technology New York D Appleton amp Co p 499 Phipps Elena 2010 Cochineal Red The Art History of a Color p34 Yale University Press New Haven and London ISBN 978 0 300 15513 6 Quilt History informational site about antique quilts and vintage textiles including article and an interactive chat group Archived from the original on 2012 12 21 Retrieved 2012 01 29 Further reading EditBuchanan Rita 1999 A Weaver s Garden Growing Plants for Natural Dyes and Fibers Courier Corporation ISBN 9780486407128 Barber E J W 1991 Prehistoric Textiles The Development of Cloth in the Neolithic and Bronze Ages with Special Reference to the Aegean Princeton University Press ISBN 069100224X External links EditGriffin Dyeworks Understanding mordants and modifiers Retrieved from https en wikipedia org w index php title Mordant amp oldid 1146329320, wikipedia, wiki, book, books, library,
