WHY DO BLACK APPER ON CLOTH WHEN IT IS KEPT WET FOR MANY DAYS ?

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Mould can  easily grow on clothes and fabric leaving black spots if we have too much moisture in our home atmosphere. clothes made of cotton or other organic materials make great food sources for mould and mildew to live on. Such spots may appear in a unnoticed shirt in our washer which is due to moist, humid temperatures in the washer.  mould spores occur naturally in the atmosphere and settle and grow wherever conditions are suitable for them. Moulds grow not only in unnoticed moist fabrics but also can grow on the surface of any kind of materials like books, shoes, bags, curtains, rugs, carpets, mattresses, wood furniture, bathroom tiles, walls and ceilings. 

  Natural fibres are particularly prone to microbial attack as they are readily digestible by bacteria and fungi, while the synthetic fibres are not completely immune. Because they may also contain some additives, that may be a nutrient for microbes. wool is more likely to be attacked by bacteria than cotton while cotton is more likely to be attacked than wool by fungi.

Many different finishes applied on textiles and dirt as well as grease human sweat and dead skin from the human are excellent sources of nutrients for microbes, making textiles susceptible to microbial attack. the most common bacteria that grow on non-dried wet clothes are Stahulococcus aurues, S. Epidermidis,  corynebacterium, Escherichia coli and Proteus Vulgaris and the cloth damaging fungi are Aspergillus niger, A. furnigatus, Stacybotrys  Chartarum,Curvularia lunota, and certain species of Cladosporium, Penicillium and Alternaria. 

     The unpleasant odour results when, among other things, human perspiration is converted by bacteria into foul smelling substances such as aldehyeds, amines, ammonia, Sulphides, mercaptans, aromatics, lactones and fatty acids. while washing such infected clothes, brushing off the mould won't be enough. we have to apply bleach to remove the mould stains. In such case we must just make sure beforehand that the said fabrics can withstand bleaching - silks woollen and items should never be bleached  non-chlorine bleaches usually work fine with all other fabrics. It is also need to wash the clothes with a good  detergent. if they are not washable we must get them dry-cleaned. as much as possible, after normal washing, clothes should be allowed to dry naturally in the sun. so the only thing to avoid black spotting is to avoid putting the soiled or still wet clothes in the closets.

source:- The Hindu