Evaluation of extraction and dye methodologies of European madder (Rubia tinctorum)

Attention is being focussed on the use of natural dyes, in part due to environmental concerns. Natural dyes have been dismissed as being unpredictable and highly variable, although these dyes have not been tested to determine if this belief is valid. The purpose of this study was to assess and promote the use of natural colorants within the context of sustainable development. Commercial use of dye from renewable resources is hampered by the lack of knowledge concerning such colorants. Adoption of the use of naturally sources colorants is further hampered by the claims concerning their inconsistency and unpredictability. Eleven methods for extracting and dyeing with European Madder (Rubia tinctorum) were selected, converted to metric and standardised. The methods were repeated ten times, with five specimens per replication. The specimens were measured with a Hunterlab Tristimulus Colorimeter in CIELAB. The data from each method was then used to calculate the mean colour difference for each method. The ATTCC test method (173–1998) CMC: Calculations of small color differences for acceptability was used to calculate ΔE cmc for each measurement. The tolerance limit where set at ΔE_cmc ≤1.2 at a 95% confidence level. For each method, there was a null hypothesis that there would be no statistical difference between the colour of each of the specimens within that method. It was found that six of the eleven methods produced results that failed to reject the null hypotheses: which means the six methods produced consistent results. This, in turn, means with standardised Practices natural colorants can be successfully utilised for the dyeing of textile and like materials.