Preserving and Storing Plant Dyes

If you wish to preserve plant dyes to use out of season (when fresh plant material is not available) you have three main options:

Drying

To dry plant material, tye it in small bunches and hang the bunches in a dark, airy place. Exposure to light (especially direct sunlight) while drying usually results in loss of colour. When the material is dry and crisp, store it in paper bags in a dry place until needed.

Freezing

If you have freezer space, freezing is a better option for preserving some plant material, such as the spent flowers from dahlias. Simply chop the plant material if it is bulky and pack it into plastic bags or containers, then freeze promptly. Use it straight from the freezer.

Extracting

Many dyes can be extracted by boiling the plant in alkaline water. Weld and Golden Rod are good candidates for this method. The extracted dye can then be precipitated from solution, concentrated, and stored in a jar. It thus takes up much less space than dried or frozen plant material.

To make the water alkaline, add Sodium Carbonate or Sodium Hydroxide, so that the pH is about 9. Boil the chopped plant material to extract the dye, then remove it and allow the dye water to cool. As it cools, the dye becomes less soluble. Add some acid (citric or acetic, for example) to the dye water to lower the pH, so that the dye precipitates.

Allow the dye to settle to the bottom of the container, then syphon off the excess water and filter the dye through a cloth. You can either allow the dye to dry (and crush it to a powder before use), or store it as a concentrated paste. When using the powder, I add a small amount of household ammonia and stir to a paste, which helps the dye to dissolve.