This experiment has been a long one. It started a month ago when I bought these crushed walnut shells from Riihivilla Web Shop. Leena has a wonderful online shop and a very informative blog about natural dyeing (also in English). The instructions said to soak the walnuts for a month before dyeing, apparently it takes a long time for walnut shells to release colour. So I did soak them for a month and quite soon the walnuts started to ferment ( I think). I wouldn’t recommend doing what I first did; I put the walnuts into a plastic container and closed it with a lid. It’s a good thing I did check on them every once in a while because pretty soon the whole thing would have exploded. So no air-thigh containers. I learned that just in time. Also after a month the smell is pretty strong.
After a month of soaking the shells, I sifted the walnut crust away and dyed 100 g of unmordanted labswool yarn. Apparently walnut contains tannin which is nature’s own mordant and using alum as mordant would not make the colour stronger, in fact just the opposite. I kind of forgot to boil the walnut shells before dyeing the yarn and that’s why my first try was lighter than my second try where I added the walnut shells to the dye and boiled the dye for one hour.
To dye the third skein (bottom right) I used the dye again and the result was the same as the first colour. I read that if you add an iron after bath you could get the colour even stronger. I have to try that sometime.