Silk is a protein fibre produced by silkworms. As a silkworm develops into an adult it feeds on leaves and then spins a cocoon from one continuous silk strand or filament, approximately 914 meters yards long. Inside the cocoon the worm changes into a chrysalis, then into a moth, which then seeks to leave the chrysalis.[1 ] The moth achieves an escape path by secreting a liquid, which dissolves a hole in the cocoon through which the moth can then escape.[2]
Heat is used to soften the hardened filaments so they can be unwound. Single filaments are then combined with a slight twist into one strand, a process known as filature or "silk reeling."
===Processing===
Cocoons are soaked in [[sodium carbonate]] to soften in preparation for reeling (unwinding the filament from the cocoon). Silk fabric is then woven with the natural gum or [[sericin]] still on the yarn, acting as a natural sizing agent. There are several reported cases of allergies to silk, although these have been traced to the remnants of sericin in the finished product. After weaving, the gum is removed by boiling the fabric in alkali. This can result in a 20% reduction of the harvested weight of the silk. Some of this lost weight is added back by saturating the silk fabric in a bath of tin-phosphate-silicate salts. These processes can create a high biological load on the water, and deplete available oxygen for aquatic species if left untreated. Exposure to tin through breathing and skin contact can have acute and long-term effects on worker health if proper equipment is not used.[6]
<br/>Lightweight silk fabrics (fine gauge silk) are prone to wear and are degraded by exposure to sunlight and hot temperatures. They can also be susceptible to abrasion and twisting in laundering.[7]
==Sources==
# http://www.textileexchange.org/node/1096# http://www.naturalfibres2009.org/en/fibres/silk.html# http://www.thehindubusinessline.com/industry-and-economy/agri-biz/govt-may-use-wastelands-for-tasar-silk-cultivation/ article4479274.ece
# Slater, K. (2003), Environmental impact of textiles: production, processes and protection. Cambridge: Woodhead Publishing, p27
# Slater, K. (2003), Environmental impact of textiles: production, processes and protection. Cambridge: Woodhead Publishing, p27
# http://www.lenntech.com/periodic/elements/sn.htm# http://www.treehugger.com/culture/qa-is-silk-green.html# http://www.greenlivingtips.com/articles/waste-decomposition-rates.html# http://hwww.theethicalsilkco.com/eco-friendly-silk/
Other:
http://www.bacsa-silk.org/en/the-prospects-of-the-european-sericulture-within-the-frame-of-the-eu-common-agricultural-policy/
ec.europa.eu/agriculture/quality/schemes/index_en.htm
http://www.cdfd.org.in/wildsilkbase/info_moths.php
greenopedia.com/article/cruelty-free-silk-fact-or-fiction
Silk is a small but exclusive [[protein fiber]] where one have the make distinguishes between cultivated silk (Silk) and wild silk ([[tussah silk]]). Silk consists of a double filament that is incorporated with a low molecular weight protein called sericin. This, together with naturally occurring oils and organic impurities, is removed in hot water at the unwinding of the cocoon. [[Sericin]], which represents 20-25% of raw silk is allergenic, which has caused problems in the use of silk waste as cushioning material. China is currently the largest silk grower.
==Environmental aspects==
Waste water from boiling silk contains a high concentration of nitrogen, organic compounds that may have bad environmental impacts. Silk was earlier sold by weight instead of per unit area and it was allowed to increase the weight by impregnation with metal salts. This " allowed cheating " still occur. The process is very energy and water consuming and provides a high concentration of metal salts in the waste water. There are several reported cases of allergies to silk, although these have been traced to the remnants of sericin in the finished product. There is Öko-Tex 100 certified silk products in the market which can ensure that no residues of sericin is still present.
==Sources==
*[http://www.jrc.es/pub/english.cgi/0/733169 IPPC BAT, Integrated Pollution Prevention and Control, Reference Document on Best Available Techniques for the Textile Industry]
*[[Textile Environmental Handbook]]