Colour fastness to acid-felting: Mild

This part of ISO 105 specifies a method for determining the resistance of the colour of textiles to the action of dilute and hot mineral acids, as used under mild felting conditions in the hat-making and felt industries.
A specimen of the textile (textiles in all kinds and in all forms) in contact with adjacent fabrics is milled in acid solution, rinsed and dried (action of dilute and hot mineral acids). The change in colour of the specimen and the staining of the adjacent fabrics are assessed with the grey scales.
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http://www.dfmg.com.tw/member/standard/bs/BS-E14.HTM