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Ecologically Sustainable Mordants

by India Flint
Posted on September 19th 2010

Remember what fun it was as a child, mixing up assorted potions in glass jars, tins and old pots or [if you were really lucky] in actual cauldrons? When I think back to the quality and substance of the vessels I was permitted to play with in the garden as a small person my knees almost go weak with desire. There were a collection of large iron cauldrons I would seriously consider giving my eyeteeth for now, as well as a substantial copper pot and the usual assortment of chipped enamel containers considered unfit for culinary use. Sadly most were discarded or given away in the course of my family’s somewhat peripatetic history. [The one pot I have left that originated from my great-grandmother’s kitchen is now ceremonially used to make beignets on rainy Sunday afternoons.]

Traditionally stainless steel has been the favoured substance when dyers choose pots, being a stable and nonreactive metal. But such clinical purity can greatly limit possibilities in the dye bath; the composition of the vessel used for dyeing is extremely important as it may have a substantial influence on the colour outcomes. Iron pots tend to darken colours and the longer the dye is left in the pot the more likely it is to become black especially if there are tannins present in the brew. Copper pots tend to enhance golds and greens – plants such as Choisya ternata [sometimes called Mexican mock orange] and Solidago candadensis [golden rod] deepen their green tones when steeped in such pots for a few days. Aluminium pots will bring out the yellows in brown onionskins but are likely to send berry and red leaf colours into blues and purples [depending of course on the quality of the water being used whereas cooking St John’s wort [Hypericum perforatum] in aluminium [and again, letting the stew sit for a couple of days] is highly likely to result in a brilliant lime green. So here we have many possibilities without even adding any extra substances to the brew!

Experimenting with pot-as-mordant can be most rewarding. The longer the dye solution is left in contact with the pot, the more radical the colour changes are going to be. An amusing exercise to try begins with the sewing of test strips made up of the usual suspects… for example cotton, silk, wool, hemp and linen. Tear two-inch wide strips of these materials across the width of the fabric and stitch them together along the long edges. Then cut across the finished work so that you end up with test strips made up of little bits of different cloth. Make up a plant dye brew in your selected pot, steep four or five pieces of cloth in the brew for an hour or so and then remove the pot from the heat. The next day take out one of the strips. Wait 24 hours before removing the next one and so on until they are all done with. You should notice some interesting colour differences between the first and the last.

Even more radical colour changes can be induced by using adjunct mordants but avoid purchasing aggressive and very likely toxic metallic salts from a chemical supply company. It’s much more fun to make mordant solutions from food wastes, harvested waters, foil packaging, scrap iron, old coins and acid-rich plants such as rhubarb and oxalis. Vinegars can be brewed from a mix of water and fruit peels. Iron solutions can be brewed by making up jars with rusty nails and screws topped up with various liquids. You might try urine, seawater, rainwater and vinegar [separately] as the substrate to brew with your found metal. Think about investigating water from wells compares with lakes and oceans. I have found that not only do the seas and oceans around the world react differently in the dye bath, even rivers within the same region will pick up different minerals as they find their way across the land.

Aluminium foil left to stew in a jar of vinegar makes a cheap alternative [although probably not pure] to purchased aluminium acetate. Old copper coins and plumbing off-cuts left to soak in urine for a few months will make a good enhancer for green dyes. It is well worth making a friend of the plumber – I have been known to trade chocolate for copper fragments resulting in a most satisfying exchange of commodities. The liquids thus made are by far less harmful than substances like Copper sulphate or Ferrous sulphate [and they are weaker and thus less aggressive to the cloth being dyed] and best of all they’re free. If in any doubt as to the danger of these traditional mordants simply wander in to your local hardware store and read the labels on the packets. The words “toxic”, “corrosive”, “do not dispose near waterways” and “not to be used for purposes other than specified on the packet” are very clear warnings indeed. While the home-made brews are safe by far, remember to ensure that they are kept out of reach of children and pets; never ever store them in containers that might be confused with ingestible substances.

To assess how you might use your potions, set up a collection of white [or clear glass] cups or glasses [acquire them at your local thrift store and keep them especially for this purpose – most importantly don’t eat or drink out of them] on a large piece of paper. The paper is for writing notes on about the contents of the containers. Half fill each container with dye solution. Keep one of them aside as your ‘control’ pot, and add small amounts [a couple of teaspoons worth] of your own-made mordant solutions to each. Write what you have added on the paper next to the vessel. Observe the changes [sometimes there might not be any at all, other times they will be extreme] and make the decisions about what you might add to a dye pot based on your observations. You might even add a small cloth sample [as described above] to each vessel and let it sit for a couple of days to see what happens over time. Alternatively use these small quantities of dye to add colour to threads and yarns for surface stitchery. Just be warned, this journey of discovery can become very addictive indeed…