I made some dye samples with red cabbage and unbleached cotton fabric. I used this red cabbage dye solution.
‘Nothing’ means I let the fabric untreated. I even didn’t wash it in water. After rinsing the fabric in water, it turned blue (the water is rather alkaline here). In a soda-water-solution, the fabric became instantly bright green. In a solution of vinegar and water, the fabric turned pink after a while.
However, all these beautiful colours weren’t very lightfast. After some days, all colours were more or less light grey-purple.
On the next dye sample, I tried different mordants, still using the same dye solution. All samples are washed in water after dyeing.
I cooked two samples in a vinegar solution (1 part vinegar to 4 parts water). On the left: unbleached cotton fabric, on the right silk.
The three next samples, I cooked in a salt solution (1 part salt to 16 parts water). On the left: white cotton fabric, in the middle: silk, on the right: unbleached cotton.
I soaked one sample in the same tannin solution as here.
I partly soaked the last sample in iron liquor. Where the fabric turned vibrant blue, I had applied the iron mordant.
After some days exposure to light and air, all cotton turned light grey-purple and the silk brownish purple, apart from the iron mordanted cotton. This sample stayed blue. This led me to experiment some more with red cabbage and iron.