Blackberries have a deep purple tone ideal for safely dyeing natural fabrics and yarn. Because the berries are edible, they are safe to use around children and pets -- you can even invite children to participate in the dyeing process. Depending on the number of berries you use, you can dye light fabrics pink, lavender or dark purple.
Separate ripe berries and place them into a stainless steel pot. Wear work or gardening gloves to prevent staining your hands and pricking yourself on thorns.
Cover the berries with water. The berry-to-water ratio depends on how dark you want the dye to be. For a light dye, use fewer berries. For a darker dye, use more berries.
Simmer the berries for ½ hour.
Remove the berries and place them in a blender or bowl. Blend the berries into a puree, or mash them with a potato masher.
Pour the mashed berries back into the water and simmer for another ½ hour.
Strain the dye into a bucket through cheesecloth or a strainer basket to remove all pulp and seeds.
Add additional hot water to the bucket if desired.
Make a separate mordant bath: dissolve 1 tbsp. alum for every 1 gallon hot water in a bucket. Alum acts as a mordant to prevent dyed fabric from fading. Allow the dye bath to cool to warm before bathing fabric in it.
Saturate your fabric in plain water.
Submerge fabric in the mordant bath for 30 minutes. Remove and wring out.
Place fabric in the berry dye bath and allow it to sit overnight.
Hang fabric on a clothesline to dry.