Sunday, December 9, 2007

Colour Fastness


Fastness is the fundamental requirement that coloured textiles should
withstand the conditions encountered during processing following colouration
and during following their subsequent useful life.
Light Fastness:
How confident are you that your fabric will perform well exposed to light or will colors fed or the fiber loosed their strength is always a question in front of most of manufactures. For some manufactures the light stability is an oblivious concern.
Degradation to textiles from exposure to light typically includes color change, fading yellowing and loss of tensile strength. If light fastness and weathering do not seem like significant consideration for particular product, this kind of damage causes millions of dollars in product losses every year.
This degradation occurs when light breaks chemical bonds in dyes and fibers. Sunlight is made up of ultra violate light, visible light and infrared radiation. While short wave UV causes most of the physical property damage to fibers, it is generally the longer wave UV and visible light that causes textile fed. This means that both outdoor product, like balloons, tents, and awnings and indoor product like apparel and curtains are vulnerable+. Even products exposed to harsh indoor lightning or sunlight through window glass in bright retail or commercial environment are susceptible.
For manufacturers of the fabric used outdoors, light exposure is one of the several concerns. High temperature and moisture in the form of rain, dew, and humidity can also be damaging. Light, heat and moisture in combination may synergistically contribute to even greater product degradation than anyone of these elements alone.

This method is intended for determining the resistance of the colour of textiles of all kinds and in all forms, and of leather, to the action of daylight.
If there is a possibility o a sample being photochromic, the test of photochromism shall be applied additionally.
A specimen of textile or leather is exposed to daylight under prescribed conditions, including protection from rain, along with eight dyed wool standards. The fastness is assessed by comparing the change in colour of the specimen with that of the standards.
1. Fabric size: 1 x 6 cm
2. Fastness rating: 1 to 8
Blue wool cloth ranging from 1 to 8
i. C.I. Acid Blue 104
ii. C.I. Acid Blue 109
iii. C.I. Acid Blue 83
iv. C.I. Acid Blue 121
v. C.I. Acid Blue 47
vi. C.I. Acid Blue 23
vii. C.I. Solubilised Vat Blue 5
viii. C.I. Solubilised Vat Blue 8

Pattern dyed with 3 dyes should be deceived after dyeing. The patterns of light fastness from 1-8 may be obtained from ISI.
The BS 1006:1978 test of day light exposure specifies that sample should be tested together with standard dyed wool patterns of light fastness. 1-8 respectively cover with opaque sheet of card board or aluminum leaving the other half exposed.
When daylight is used fading is slow and quicker answer is often necessary under commercial purpose. Hence, xenon arc lamp is used. The SED of this lamp bears a close resemblance to a natural light.
Test reports:
Report the numerical rating for light fastness. It is represented by the figure alone (in the case of using the standards denominated 1-8).If this rating is equal to or higher than 4 and the preliminary assessment is equal to or lower than 3, report the later figure in brackets. If the specimen is photochromic, the light fastness shall be followed by bracketed P along with the grey scale rating.

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