Leather Test Methods for Colorfastness and Color Measurement

Published: 21st January 2010
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The discolored results of numerous machine washings and the Early fading of manufacturing textiles are indications of a lack of quality. This is why color fastness tests are gaining international significance.



There are a quantity of test methods habitually used for colour fastness and for dyes. The more significant are:



- Grey Scale for Assessing Change in Colour: This Grey Scale is for assessing changes in colour of leather in colour fastness tests, for example, wash fastness, perspiration fastness, etc. The scale consists of nine pairs of grey colour chips every one representing a visual difference and contrast.



- Grey Scale for Assessing Staining: This Grey Scale is for assessing the degree of staining caused by a dyed leather in colour fastness tests. For example, the staining of wool and cotton fabrics in the wash fastness, perspiration fastness, etc. The scale consists of nine pairs of grey colour chips each representing a visual difference and contrast.



- Colour Fastness of Leather to Light: This method is intended for determining the resistance of the colour of leather to the action of a standard artificial light source. The Xenon lamp has an emission wavelength profile close to daylight. The side to be tested of the leather sample is exposed to light from a Xenon Lamp, under controlled conditions, along with eight blue dyed wool standards (blue scale). The light fastness is assessed by comparing the fading of the leather with the fading of the blue standards. The fading is typically made in 2 exposure times to better assist the evaluation.



- Colour Fastness of Leather to Mild Washing: Fastness of the colour of leather to hand washing is the resistance to washing under mild domestic laundering in water. In washing leather, not only changes in colour can

Occur in the leather, but coloured substances may bleed from it and may stain adjacent textile materials.



- Colour Fastness of Leather to Machine Washing: Fastness of the colour of leather to machine washing is the resistance to washing under domestic machine laundering in water. In washing leather, not only changes in colour can occur in the leather, but coloured substances may bleed from it and may stain adjacent textile materials.



- Colour Fastness of Small Samples to Dry Cleaning Solutions: This method is intended only for determining the resistance of the colour and the finish of leather to dry cleaning solutions. It does not cover the suitability of composites or complete leather garments to dry cleaning processes.



- Colour Fastness of Leather to Migration into Plasticized PVC: The colour fastness in respect of migration into plasticised poly(vinyl chloride) - PVC - is the transfer of colour from leather to white plasticised PVC at 50 C. The side of the leather sample to be tested is placed on a white pigmented sheet of

Plasticised PVC and the composite specimen is exposed to heat under pressure in an appropriate apparatus for16 h at 50 C.



- Colour Fastness of Leather to Perspiration: By fastness of colour of leather to perspiration is meant its resistance to the prolonged action of an artifical perspiration solution.



Another way of test is Chrome-free leather. This leather has gradually gained commercial importance, particularly for automobile upholstery applications. In many respects, however, chrome-free leather is inferior to chrome-tanned leather. UV and heat are known to be more detrimental to chrome-free leather than to chrome-tanned leather, especially in regard to the colorfastness of dyestuff and mechanical properties. Temperature, UV radiation, and humidity are key environmental factors that affect leather properties. The role of humidity and its interaction with UV radiation and temperature on leather properties, however, are not clear to the leather industry, and this information is needed for formulation of antioxidants that will protect chrome-free leather from UV and heat damage.



Daniel Garcia is manager of Ibertest Internacional - Materials Testing


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