I only knew one type of Rhubarb; the sour, rich red compote my English aunt introduced us to. Eaten with clotted cream or in a tray bake with delicious crumbs on top. The tart, sour taste that makes your mouth wrinkle compensated with a lot of sugar. In Israel I was able to find it for a while, years ago in a super market chain, but that got discontinued.
Only when I started dyeing fabrics I learned that it was the root that could be used for some really nice dye on all types of textiles. And it was only when I started looking for Rhubarb Root to import as part of my collection of natural dyes, that I understood that there are many, many varieties of Rhubarb, some of them with the most enchanting names like Glaskins' Perpetual and Riverside Giant.
It turns out that the dye is found mostly in the more ornamental varieties of rhubarb that grow in India, Tibet and Nepal, called Reum Emodi. It is known for its’ Ayurvedic medicinal properties; Rheum Emodi leaves are a mild purgative, astringent, tonic, laxative, stomachic. Powdered rhizomes are said to be sprinkled over ulcers for quick healing. It is also reported to be a potent anti- inflammatory drug*.
The dye produced from the dried and ground roots is both a mordant and a dye. It contains oxalic acid which is toxic, and should not be ingested.
Oxalic acid is toxic because of its acidity (my Rhubarb Roots turn our rather alkaline water with a ph of 8, into a very acid 4), and its' chelating properties, meaning it will bind iron, lead, or copper in the blood.
Scary? No, just don’t eat it and boil dyes in a well ventilated open space and do not inhale the fumes. The colours are well worth it.
Rhubarb roots give a wide range of colour by changing acidity after, or during dyeing. I have made some samples to show the results. An acidic after bath shifts colours to yellow. A little soda ash creates wonderful oranges to brick reds. The dye is very lightfast!
Making the dye bath
This is straight forward; measure the dye according to WOF; 2-6% WOF of the rhubarb extract or 20% WOF for regular powdered roots. Heat slowly in a non reactive pot that can hold all the fibres easily, and boil for around 30 minutes to one hour to extract all the dye. Let cool and re-heat with protein fibres to 45 degrees celsius and hold for 90 minutes, stirring softly regularly to distribute dye evenly.
You can use Rhubarb Root for my Low Impact Method but make sure you use gloves. Left overs can be recycled in a regular dye bath or just keep adding bits of water for new paste.
This is Rhubarb straight out of the dye pot, no mordant and no modifier;
This is the same batch but rinsed in water with juice of half a lemon as an acidic modifier; much more yellow tones
And last but not least; the Alkaline modifier.
Imagine what this will do as an under-dye for Indigo?
A little bit of rhubarb will dye a lot of fabric, which makes it a very cost effective dye. One bath can easily dye three batches. 2-6% WOF of the rhubarb extract or 20% WOF for regular powdered roots is sufficient.
It doesn’t need a mordant but for additional shades you can use;
Alum mordant at 15% WOF for protein fibres.
Cellulose mordant with tannin at 5% WOF and then alum at 15%, or aluminium acetate at 8%.
*(Disclaimer: Please never self medicate and always consult a physician)
סוזמנ דקל אקו פרינט וצבעים טביעים