The Light Fading Mechanism of Dyes Derived from Rhubarb Extract

The effect of relative humidity and mordanting on the fading kinetics and colour change of dyes derived from rhubarb extract on wool and silk has been investigated. Wool samples showed negligible change in colour even after 100 h of exposure, whereas silk samples became significantly darker. Relative humidity in the range of 10 – 45 % and mordanting did not appear to affect the rate of fading on both the fibres. However, the rate and extent of change of colour (deltaE) on exposure was different for different mordants. The high resistance of the dye to light fading indicates that the dye is present in a highly aggregated form in silk and wool