Jack 'n' Jill and their jaded jeans

Tag : indigo jeans

By: Naresh M. Saraf and Deepak V. Alat


Jack 'n' Jill, after returning from the hill, have grown intoadolescent teens. Like any other member of the community, they hadtaken up to jeans as a symbol of youth.


Things went well for quite some time, as they started with basicdenim. Then the new fashion came, where pre-bleached, faded denimswere in vogue. So they bought new pairs. Jack went to town insearch of a job while Jill went to the beach with her friends toenjoy her freedom. After one week, when both returned to theirvillage and, to their dismay, both their bleached jeans had turnedyellow!


Jill tried to wash them, though she is not supposed to wash jeansat least for one lunar month, but the dirty yellow tinge remained.She discussed the problem with her friends, teachers and learnedmen and women in village but could not find satisfactory answer.


A visiting consultant told her it was phenolic yellowing, which hehad heard about from some other consultant.


Finally she approached a professor of textile chemistry. He askedthe background details and concluded that this is nothing but OzoneFading!


He narrated his experience and findings, which were fascinating andenlightening to both Jack 'n' Jill.

Indigo dyeing is carried out on continuous ranges, either in sheetform or in rope form.


Unlike conventional dyeing, this kind of yarn dyeing is inring-dyed form, where dyestuff is not allowed to diffuse inside.


The ring-dyed yarn leads to a faded look on usage, because of lossof colour due to abrasion or wear a tear. Fading can also beenhanced artificially in garment form, by either mechanical,chemical or enzymatic assistants.

Unfortunately these fashion garments are prone to yellowing as aresult of decomposition of indigo (Isatin and Anthranilinic acid)due to environmental influences. This yellowing is an irreversiblephenomenon. The destruction of indigo is due to NOx and oxidants,particularly atmospheric ozone, which is, major cause of yellowing.Ozone is present naturally in air near the seashore, where thereare fewer pollutants. Apart from giving a feeling of freshness tothe holidaymakers, ozone also silently fades the denims. Inindustrial cities, chemical smog along with ozone is the mainculprit in the yellowing of denims.


Two types of smog have been reported in literature. 'London smog'is caused by soot particles am sulphur dioxide. These particlesabsorb part of sunlight, making a visible' smog. Sulphur dioxide inthis smog is capable of destroying indigo. The second type of smogis called 'LA smog' and is invisible. It consists of nitrogenoxides from automobile exhausts. This is also called a'photochemical smog' and is present usually in the summer monthsand in populated areas with heavy automobile pollution.


Due to the depleting layer of natural ozone, the sun's UVradiation, mainly shorter wavelengths, increasingly reaches theearth's surface in the summer months. The UV light reacts withnitrogen oxides as we as oxygen in the air to form an ozonemolecule, which is unstable. The ozone thus formed destroys indigo.Since ozone generation is continuous process, yellowing continues.


Based on the molecular weight of Ozone and Indigo, theoreticallyapprox 1 gm ozone can destroy 10.9 gm of Indigo. Apart from ozone,nitrogen oxides present in air also destroy indigo.