Buckthorn bark (Rhamnus spp.) is an extremely useful dye which can be used very successfully without a mordant and gives colours ranging from mustard yellows to true madder-type reds. (The bark of alder buckthorn (Frangula alnus) can be used in the same way as buckthorn bark and gives similar colours.)
For reds, buckthorn bark is best processed using the alkaline extraction method, which means soaking the bark in a solution of water and an alkali, such as washing soda or wood ash water. The exact proportions of water to alkali don’t really matter as long as the solution has a pH reading of 10 to 11. As the solution begins to ferment it will become more acidic, so more alkali may need to be added to maintain the degree of alkalinity necessary for reds and pinks. If fibres are added at different stages, a range of shades can be obtained, with colours becoming more orange and less pink in tone as the alkalinity decreases. No heat should be applied to solutions with high alkalinity and the colours develop gradually on the fibres in a cool solution.
The fibres can be added together with the buckthorn bark and left to soak with the dyestuff until a suitable depth of colour has been reached. Alternatively, the dye solution can be poured off once the colour has developed and the fibres can be added to this dye solution. Whichever method is selected, no heat should be applied.
This photo shows some of the colours achieved from buckthorn bark using the alkaline extraction method described above. (No mordant)
This photo shows some colours from the exhaust dye bath. (No mordant)
The alkaline extraction method is a very useful way of extracting and applying colour and can be used with a variety of dyes. It is one of the techniques I shall be featuring in my new book “A Heritage of Colour”, which is currently scheduled for publication in February 2014 and which will include details for using over 50 plants, including buckthorn. I will give more details about this new book in a later post.