Correct dye analysis can be very important in characterising old textiles but is frequently, compiled by natural ageing. Textiles may have either been exposed to light or been buried, thus changing the dye colour. The dye colour. The presence of a mordant is an additional complication. In this investigation, wool and silk fabrics were dyed with alisarin, brasilin and carminic acid. The five metal salts uses as post mordants were potassium aluminium sulphate, stannouschloride, copper sulphate, ferrous sulphate and potassium dichromate. Details of sample preparation are given. The sample were exposed to simulated sunlight or simulated burial. Colour and tensile measurements were carried out and tabulated. The change that occured are dependent on the fibre type and the dyemordant combination used. Light-induced changes are also different from burial-induced changes. The information can be used to predict possible vulnerability to change during exhibition. References -- ICCROM