I’ve been trying out two more extracts, rhubarb root & cutch waste. Rhubarb root is a useful & versatile dye, so I was pleased to see that it is available in extract form from Pure Tinctoria. Among the other extracts on their list I came across “Cutch Waste”, which intrigued me. Cutch, rather than cutch waste, gives rich browns on all fibres &, like rhubarb root, can be used without a mordant. Cutch is one of the few dyes that has been available in extract form for very many years. In fact, I have never come across cutch in any other form. It is produced by simmering the heartwood of Acacia catechu (native to India & SE Asia) in water, then reducing & evaporating the liquid until it becomes very thick. It is then poured onto matting & left to dry & harden into a solid mass, which is cut into chunks, then powdered. Just where the cutch waste comes from, I’m afraid I don’t know. Another puzzle to be solved!
I first came across rhubarb root as a dye some years ago in an article in the Weaver’s Journal. The article was about Tibetan carpet weavers working in Nepal, for whom rhubarb is a vital dye plant. The leaves contain oxalic acid, which they use as a kind of mordant or base for other colours. They also add rhubarb leaves to organic indigo dye vats to assist fermentation. The rhubarb root is used for yellows, rusts & as an addition to brighten madder dye baths. The article suggested alum might be difficult to obtain in Nepal, unless from plant sources such as the leaves of plants that absorb aluminium from the ground, & therefore most dyes were used without a mordant. So I experimented widely with rhubarb root on unmordanted fibres, as it is so useful to have a source of yellow that doesn’t require a mordant, especially in order to obtain a green when overdyed with indigo. However, I have to say that, although rhubarb root dyes wool & silk excellently, it is less effective on cellulose fibres.
I tested both these extracts on wool without a mordant & with an alum mordant. Both fixed well without a mordant. The rhubarb root produces a clearer yellow without a mordant & a more mustard shade on an alum mordant. The cutch waste shade is an attractive soft greyish green, (more green than grey, however) very useful as a contrast to more vivid colours. Unfortunately, the photo doesn’t really do justice to the colours.
Rather foolishly, I didn’t try out any colour modifiers with these extracts. I don’t know why, as I usually do a full set of tests. Rhubarb root in its plant form reacts well to modifiers. It gives moss green with iron, a brownish (taupe?) shade with copper & shades ranging from red-brown to red with an alkali such as washing soda. Truly a versatile dye. (More details on using modifiers in the entry about dahlias.) So now I must do these tests with the rhubarb root extract, to see if it reacts in the same way.
In my experience, not all extract dyes respond as well to colour modifiers as their plant counterparts. I think this is because some extracts are treated during the production process to reduce their sensitivity to changes in pH values & thus make the colours more stable if washed, or otherwise treated, in a non-neutral medium. I routinely wash naturally dyed fibres in dishwashing liquid & I have yet to find a dishwashing liquid that is not pH neutral when in solution. Some extracts are also probably treated during manufacture to remove some of the less desirable pigments. This would explain why madder extracts vary so much from one production company to another. The more recent Earthues madder extract gives a wonderful clear rich red, while their earlier madder extract was much more orange in tone. Some other madder extracts also produce more orange/coral tones, which can be made pinker/redder in tone by using a washing soda after-soak – but NO heat particularly if dyeing wool.
More about extracts when I’ve done some more tests.