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History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c20.s1: Mordants

History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c20.s1

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English

Mordants

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Dyes which have little or no affinity for certain substances may yet be fixed on them if a mordant is first applied. Mordants are substances found to be capable of penetrating and adhering to fibres. Since wool and silk have both acidic basic properties, they are easily dyed. But dyeing cotton is difficult as it requires the prior use of mordants. The dye added after mordanting forms an insoluble product in the cotton fibres.

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The discovery of a fragment of a maddar-dyed fabric at Mohenjo-daro is a strong evidence to prove that the mordant process of dyeing cotton cloth was known in India 5,000 years ago. The hundreds of references in our ancient texts about dyed cotton fabrics in different colours with different floral and geometrical designs suggest that dyers of ancient India knew the use of mordants and selection thereof for different types of textiles.

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Early in the 6th century A.D., Varāhamihira has alluded in Bṛhat Saṃhitā to the preparation of fast dyes for textile fabrics by the treatment of natural dyes like mañjiṣṭhā with alum and other chemicals (like sulphate of iron, kāsīsa in Sanskrit) as also with cowdung⁵. Tuvarī (alum) is described as colour-binding substance of maddar. It is well-known that alum and sulphate of iron are even now largely used as mordants.

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Tuvarī or alum is described as a fragrant earth produced in the mountains of Surat in Saurastra and which dyes cloth and fixes the colour of maddar. It is called saurāṣṭrī also and when applied to white cloth it serves as a mordant for dyes. A variety of it is slightly yellow and is called pītikā and another variety sphuṭikā is soft and acidic⁶. The two varieties of tuvari are also called phullikā and khaṭikā⁷. In Amarakośa of 600 A.D., kāṅkṣī, tuvarī and saurāṣṭraja are mentioned as synonyms. Since a large number of dye-stuffs and dyed textiles are mentioned in ancient texts, it becomes evident that dyers were using basic mordants like iron sulphate and aluminium sulphates for acid dyes and that for basic dyes, acid mordants like tannic acid were used.

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Since all dyes are not soluble in water, they have to be rendered water soluble by reduction or they have to be synthesised on the fibres (usually cotton) by means of methods like diazotization. Indigo or nīlī which have been very popular ever since the pre-Christian era and was an article of export to Egypt and other countries, is also an insoluble dye (vat dye) and our ancients knew the technique of making it soluble by reduction with which the dye could be impregnated in the cotton fibres by exposing to air or by oxidization. Besides alum, iron sulphate, etc., rind of lemon, flower of cotton, lime, lemon, green dried mangoes, myrobalans etc. were also used as fixing agents or mordants. Mordanting effect of each varied and each one influenced that final colour obtained. In some dyes, alum produced yellow colour, in other it yielded orange blue (Jaggi, I.p. 165)

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