As I have recently been working on an article for “The Journal for Weavers, Spinners & Dyers” on using natural dyes on vegetable fibres, I thought I’d write a few words on the subject here.
There seems to be a fairly common belief that dyeing cotton and other cellulose fibres with natural dyes is often less successful than dyeing animal fibres, such as wool. This may be because some dyers use the same mordanting methods for all fibres, rather than selecting methods appropriate to each fibre type, and this can lead to disappointing results. However, using natural dyes on cellulose fibres has become simpler and less labour-intensive since aluminium acetate is now more widely available in the UK. Before the arrival of alum acetate, the alum-mordanting method generally used for best results when dyeing cotton or linen has probably been the 3-step tannin/alum/alum (or alum/tannin/alum) method, which takes several days to complete. This involves treating the fibres in sequence with both tannin and alum sulphate, the latter plus washing soda. Some dyers favour completing the tannin process first, followed by two treatments with alum and washing soda, while others prefer to carry out the tannin process between the two alum treatments. I don’t think it really matters which sequence one chooses. Some dyers may opt to use only the alum sulphate plus washing soda step and to omit the tannin process completely, although in my experience this tends to give less satisfactory results, unless the cellulose fibres being treated have a natural tannin content, as may be the case with raffia. (See my earlier post: “A Natural Dyeing Project in Uganda”)
Detailed recipes for mordanting vegetable fibres are given in my books, so I won’t repeat them here. However, I would suggest that dyers who haven’t yet tried alum acetate as a mordant for cellulose fibres might find it worth while experimenting with the following mordanting recipe:
Use 5% alum acetate (or 2.5 tsps per 100gms/4ozs dry weight of fibres). Dissolve the alum acetate in boiling water and add this to cool water in the pot, stirring well. Then add the wetted fibres, plus more water if necessary to allow them to move freely in the solution, heat to simmering point and hold at this temperature for one hour. Then turn off the heat, leave the fibres to cool, preferably overnight, and then remove them and rinse them well. (Note: alum acetate is available from some of the suppliers listed on my blog under “Useful Websites”)
I have found this mordanting method gives good results on cotton and other vegetable fibres. It is also suitable for silk, but not for other animal fibres, and is widely used in Japan as a mordant for silk. I used it to mordant fine silk fibres when dyeing silk for handweaver Maggie Stearn and found it most successful. (See my earlier post: “Maggie Stearn – Handweaver”)