Various plant pigments
Hundreds of plants can be used to extract pigments and dyes, forming the most vibrant colours you can imagine. Below are some general guidelines and useful resources on harvesting, extraction and binding.
Natural dyer Lucila Kenny: 'For centuries, plants have been picked, raised and processed for nourishment, embellishment and healing. It seems that in every part of the world where humans have lived, we can find a body of knowledge based on the powers of herbs, roots and flowers. This unique relationship between plants and people still remains in our ancestral memory waiting to be rediscovered. Such a quest will take us from the world of materials to a symbolic realm, where chemistry becomes alchemy, and colours manifest their powerful connection to the earth.'
Like all plants, painting plants can be cultivated as long as the correct growing conditions are present, an important aspect is the composition of the soil. Potting soil can be used for the first year, but it’s preferable to use a specific soil composition after that. For example, half sand, half garden soil, or half clay half garden soil. The direct surroundings determine the humidity and the amount of sun and shadow. In nature, different plants occur together in one area and plants that can’t grow well in each other’s presence, don’t grow there. When cultivating plants this is something to consider.
Harvesting: the pigments aren’t readily available inside the plants. At first only preceding substances exist and only later a specific pigment, of which the production changes at different periods during the seasons. The hue of the colour is influenced by the time of harvest. Roughly, roots and bark are best harvested during autumn; when the whole plant is used it should be harvested shortly before or during bloom, leaves are best harvested before bloom. This can of course differ per plant.
The production of natural paint or ink is done in two steps: first, the dyestuff, consisting of colourants or pigments has to be extracted from the plant, after that a binder can be added, depending on the desired application.
Extraction: There can be big differences between plants in the method of extracting the dyestuff. On the one hand, this is because dyestuff from different parts of the plant are used; on the other hand, the chemical background of the dyestuff plays a role. An example is the red/purple colourant that is harvested from the plant Alkanna tinctoria, this colourant (alkannin) is a napthoquinone. Colourants in this chemical group are often not or slightly soluble in water; when extracting this colourant from the plant, it’s better to use oils.
Take caution: poisonous painting plants exist as well. Always process dyestuff separately from places where food is prepared.
For colourants soluble in water we can form a general recipe. Note, the method can differ per plant.
1. The part of the plant that contains the colourant can be harvested fresh or dried after harvest for later use.
2. The surface area of the material can be enlarged by grinding or cutting the material. This makes extracting the colourants easier.
3. Next, the material needs to soak for a few hours or a night and optionally, cook.
4. The fluid is stained to separate the ‘pulp’ and the water now containing the colourant.
5. This fluid can be boiled down in a bain-marie to a higher concentration of the colourant. By boiling it down to a dry mass, the colourant can be preserved better.
The obtained colourant can be used for experimentation. Some colours become more saturated by using natural substances like courgette, cucumber or pumpkin juices. The brightness of the colour can be influenced by changing the acidity using for example vinegar, lemon juice or soap.
Some pigments aren’t soluble in water. Other methods are needed for the extraction of these colourants.
Binders: Colourants solved in water can be used as ink without any additives. Though often a binder is desirable when using dry pigments or dried colourants, for example. A binder can also help get the right viscosity for silkscreen or lithography.
Information submitted by the maker and edited by the Future Materials Bank.
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