Mordants ancient

L. alumen, alum) The ancient Greeks and Romans used alum as an astringent and as a mordant in dyeing. In 1761 de Morveau proposed the name alumine for the base in alum, and Lavoisier, in 1787, thought this to be the oxide of a still undiscovered metal. 

The yellow dye curcumin, [458-37-7] (Cl Natural Ye//oii> 3 Cl 75300) (41), also known as tumeric, occurs in the roots of the plant Curcuma tinctoria found growing wild in Asia. The dye was well known to the ancient Romans and Greeks who used it to dye wool, cotton, and silk. The dye is an oil-soluble bright yellow material, and is the only natural yellow dye that requires no mordant. It finds use as a colorant for baked goods such as cakes. 

Direct and Mordant Dyes. The ancient dyes (see Fig. 77) may be classified into three main groups direct dyes, mordant dyes, and vat dyes (see... 

Finally, two ancient textiles of the sixteenth and seventeenth century were studied. The presence of molecular ion at m/z 263 and fragment ions at m/z 235 and m/z 247 demonstrate that indigo was used (Figure 15.7). No mordant-related peaks were detected. Lee et al. explain that indigo has so strong an affinity with the fibres that it could be used without mordant. 

The word crystal often meant with the ancients quartz crystal, but it is very evident that with the authors of these notes the term was used in a more comprehensive sense to include other transparent or translucent stones. This use is very evident in the many recipes for imitation of precious stones, where the processes involve a degree of porosity or absorbent power towards colored solutions not possessed either by quartz crystal or by glass, while certain agates, micas, alabasters or other stones possess this property. In case of the above recipe, it is doubtful whether any such mordanting would in a reasonable time roughen the surface of real quartz crystal adequately. The quicksilver here mentioned is evidently the same substance of pearly luster previously referred to. 

The processes start with some stone presumably cut to form before coloring. The stone whether mica or so-called crystal, or other stone, is either submitted after cleaning and mordanting to a color bath, whereby color is absorbed into the texture of the stone, or in some cases submitted only to a superficial stain or varnish. It is evident that some of these stains must have been more or less evanescent, depending upon vegetable dyes, while others may have been relatively permanent. It is not to be taken for granted that all the stones used were transparent or colorless before treatment, as many of the precious or semiprecious stones valued by the ancients were not transparent. 

The Lantern of the Hand at the ring finger is Alum. Properly speaking, Alum is a vitriol being the double sulfate of potassium and aluminum KA1(SC>4)2, but has been such a versatile mineral since ancient times that it s in a class of its own. It has been used for cleaning and deodorizing, as a mordant for dyes, to prepare leather, and as an astringent and styptic to close wounds. 

The roots of Rubia tinctorum have been used for dyeing textiles in many parts of the world since ancient times. Madder was widely cultivated in Western Europe for the dye industry until the beginning of the twentieth century. Rubia tinctorum contains useful anthraquinone mordant dyes. Dried roots of madder contain the hydroxy anthraquinones alizarin, pseudopurpurin, rubiadin, purpurin, purpuroxanthin and some minor anthraquinones. Anthraquinone derivatives are good mordant dyes if they satisfy the following conditions ... 

Chemically related to brazUin are the yellow mordant dyes, luteolin and morin. Both are flavone derivatives whereas the former is obtained from yellow weed or weld (Reseda luteola L.), which grows widely across Europe, the latter comes from dyer s mulberry (Madura tinctoria, syn. Morus tinctorius L.). Alum- and tin-based mordants from luteolin produce a beautiful true yellow on all textile materials. Apart from weld, saffron (Crocus sativus L.) used to be the most important yellow colourant. The ancient Greeks and Romans used the dried stigmas from this species of crocus to obtain crocin, which was absorbed onto textiles with an alum mordant. Like saffron, curcuma (also known as turmeric) serves as a colourant for foodstuffs (e.g. for mustard and curry), and as a somewhat acrid spice in Oriental and South-east Asian cuisine. Curcuma is obtained from the root nodules of, for instance. Curcuma longa L., which is cultivated in plantations in China and the East Indies. 

Kermesic acid an anthraquinone, m.p. 250 °C (d.), which occurs naturally as a bright red insect dye. It is structurally closely related to Carminic acid (see) it possesses the identical structure of a tetrahydroxyla-ted methylanthraquinone carboxylic acid, but there is no C-glycosidic glucose on C2. K.a. makes up 1-2% of kermes, the dried bodies of female scale insects Kermococcus ilicis. Kermes is one of the oldest known dyes and was used in ancient times as a scarlet mordant dye (Venetian scarlet), It was supplanted in the 16th century by cochineal. 

An interesting variation on the chelate formation of alizarin derivatives is the production of Turkey red, a brilliant red dye known from ancient times. Recipes for its production insist not only on aluminum, but on lime, in order to achieve the red-purplish color and the high fastness properties for which it is famed. Its probable structure is shown in Figure 8 10), Some modem mordant dyestuffs derived from alizarin are shown in Table IV. 

Although the chemistry of ancient dyes and mordanting processes was developed empirically, today we understand much of it in terms of modem coordination theory. However, many aspects of color shifts still await investigation. 

The desire of people to colour their clothes resulted in the development of some chemical processes. It was known in ancient times that to render a dye fast the fabric must first be treated with a mordant to bind the dye to the cloth, and that the alums provided excellent mordants. Alums occur naturally quite widely, but they often contain iron salts, which would introduce an unwanted colour in the dyeing process. Although direct evidence is lacking, it would seem likely that even in ancient times alum was purified by a recrystallisation process. 

The employment of natural dyestuffs dates back to antiquity and many of these probably arose from wood or bark. Most gave a dull brown or a yellow color, but the discovery of mordanting in ancient Hindustan and in the Orient resulted in brighter, more permanent colors. The first mordants were aluminum sulfate and iron sulfate. Knowledge of these spread westward to Egypt, Greece, Rome, and Europe. With the subsequent importation of log-wood, brazil wood, and other materials from the New World, the natural dyes became increasingly important until they were replaced by synthetic dyes (29). 

Some examples of mordants are salts of aluminum, copper, iron and chromium in each case it is the metal ion that is the mordanting agent. A comprehensive table showing the effect of mordanting on plant dyestuffs from ancient Israel is in reference [38]. Numerous other chelates are known, and their usefulness spans the various branches of theoretical and applied chemistry and allied fields. 

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