Calcium carbonate is also referred to as chalk, this dense, white powdery mineral is a common addition to the madder dye bath to deepen shades and is one of the principle minerals that create hard water. It may also be used with weld extract to bring out the bright, rich yellow shades.
- 250g is enough for many dye baths and when used as a post-bath for aluminum acetate mordanting.
The recommended amount of chalk is 5% of the weight of fiber, or 1 rounded teaspoon for 100 grams of fiber.
For calcium carbonate bath:
- The above 100 grams/4 ounces of mordanted fiber
- 5 grams/.17 ounces./1 rounded teaspoon calcium carbonate
Mix the chalk with boiling hot water and add to a bucket or container large enough to hold your goods. Add yarn or fiber and leave for 5-30 minutes. Remove, rinse lightly and proceed to dyeing. Chalk can shift dye colors due to it’s higher pH, so we like to rinse it prior to use.
You may leave the fibers in the mordant solution overnight, then extract excess water and proceed to dyeing. Some dyers feel this increases the depth of shade of the finished piece. You may store damp mordanted fibers in a plastic bag and refrigerate up to 7 days, and cure or age, as this also seems to increase the depth of shade in the dyed fibers. You may also dry and store mordanted fibers for future use; we recommend using cellulose mordanted fibers within 6 months of mordanting. Label and store your mordanted fiber and keep it away from dust or dye powders, as it is vulnerable to staining.