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RDREP01
POTENTIAL FOR COLOURANTS
FROM PLANT SOURCES
IN ENGLAND & WALES
ST0106
ARABLE CROPS &
HORTICULTURE DIVISION
by
Mary Hancock, ADAS Boxworth
Boxworth, CAMBRIDGE CB2 8NN
October 1997
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RDREP01
CONTENTS
Summary
4
Recommendations
7
1. Definition and types of dyes
8
Colourant types
10
Synthetics
10
Natural dyes
10
Source
15
Dye yields
16
Post-harvest processing and handling
16
2. Legislation
20
Pollution
20
Health hazards
22
Other environmental problems
22
New chemicals
22
Uses of natural dyes
23
3. Textiles
23
4. Food and drink
26
5. Inks and paints
32
6. Other uses
35
7. Markets - type and size
36
8. Market requirements
41
Textiles
41
Food and drink
43
Inks and paints
44
Other uses
45
9. Plant species as dye crops in the UK
46
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RDREP01
10. Acknowledgements
49
11. References
49
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RDREP01
SUMMARY
1.
Dyes and pigments found in plants have been used for centuries for colouring materials.
The dye molecules may function in the plant as colourants and/or in other roles, eg, in
photosynthesis.
2.
The use of natural dyes in the UK and the rest of the Western economies has been replaced
commercially by synthetic dyes, based mainly on aniline and using petroleum or coal tar as the raw
stock. The range of synthetic dyes available is large and the dyestuff business is worth
approximately £2.5 billion per year world wide.
3.
Natural dyes represent an apparently more sustainable source of colourants than their
synthetic counterparts, which are derived from non-renewable resources.
4.
The yield of natural dyes from a plant source is usually low compared with the yields
expected of modern synthesis processes. Their tinctorial strength tends to be less than that of
synthetic dyes which means that a greater weight of plant material would be needed directly for use
or for extraction of the natural dye than of the synthetic dye in order to obtain the same depth of
colour. Thus any large-scale use would require many hectares to be cultivated with the plant
species and the disposal of relatively large volumes