Silk, in particular, has an affinity for plant dyes, and colours beautifully.
Multicoloured yarns for knitting and embroidery can be very expensive to purchase and quite simple to dye. Silk, in particular, has an affinity for plant dyes, and colours beautifully.
Plant vs protein
Silk and wool can be dyed without pre-mordant; however, cotton, linen and other cellulose fibres should be pre-mordanted first for efficient dye take-up.
A simple way of dyeing multicoloured yarns for craft uses is to take a hank of yarn (I usually use silk) and lay it out in a flat food storage box.
Then take small quantities of concentrated dye solutions and carefully apply these to chosen areas, making sure there are distinct colour areas. Where dye solutions meet there will be interesting blends and new colours may form as a result of chance cocktails. When all of the silk has some colour applied, seal the storage box and let time work its magic. Leave it for at least a few days, preferably for a week. If you plan to leave it for longer periods of time, monitor the contents regularly! Once the dye begins to decompose (which can happen quite quickly in warm weather depending on the dyes — eucalyptus dyes can be left for months, whereas ice-flower dyes have a much earlier use-by date), things can get a bit smelly and this is best avoided. It is good practice to freeze the entire box from time to time if you want to leave the dye in contact for an extended period.
Pre-mordanting the skein of silk may help dye take-up and will influence the intensity and shade of colour achieved.
When the depth of colour is to your satisfaction, place the hank or skein in a strainer and gently spray with water using a hose. When the water runs clear, squeeze out excess moisture and hang the skein in the shade to dry.
Immerse the skein of silk or wool entirely in a dye-bath. After processing as desired, and when the skein is dry, tie off areas using the resists described above and immerse in another dye-bath. Continue these processes with successive overdyes as desired. A final rinse in a dilute vinegar-and-water solution will restore soft handle to the fibre.
If the skein is partially pre-mordanted with various substances, the diversity of colour will be even greater.