Photos. Henrietta MillerWool yarn, which I sourced from charity shops, dyed with Weld and Indigo. The colours really were this strong. Although Indigo is a substantive dye, I pre mordanted all of the wool with alum, as I did a large batch, suitable for any of the dyes. It seems that dyeing fabric and yarn is a summer activity and that crocheting and knitting is something which I mostly do in the autumn and winter months.