Sometime fibres do not absorb all the available dye colour in the dye bath, so there is enough left for a second batch of fibres. This second batch usually dyes a paler shade. This second bath is called the 'exhaust' dye bath. (Dean, 1999, 47)
One way I have thought about increasing the sustainable use of natural dyes is to exhaust the dye bath through multiple dyeing sessions. This not only means more fibre is dyed with a smaller amount of resources, but also reduces the amount of dye material that is disposed of.
Following my decision to use yarn that was already grey thanks to the natural colour of the fleece, I dipped a couple of mini skeins in my woad vat from a couple of days ago, as it still looked ok. One skein was dipped 4 times, the other 8, and there was a noticeable change from the grey/brown to a grey-blue, particularly on the one that was dipped 8 times.
I had frozen the walnut husks I used a couple of weeks ago as I had read somewhere that the husks could be used again (I can't remember the source or now locate it - terrible behaviour!). I soaked them in water for four days as I had before, then simmered for an hour before draining the husks. The dye liquid was noticeably paler than last time.
Using my usual simmer method, the result on the white fibres was a sandy colour, very different to the original deep brown that I achieved from the first dye bath.
However, as the result was so pale, you could argue that it was not worth using the water/electricity to do this. I did also dip the skeins in the woad vat a few times, but it was definitely dead by this point!
- Burns, R. (2017) Exhaustion 1-4. (Own Collection)
- Dean, J. (1999) Wild Colour. London: Octopus.