We are specialists in Persian carpets
When talking about hand-knotted rugs, there are three types of dyes to consider: vegetable (plant and insect dyestuffs), chromic (which may be synthetic or natural-based) and aniline. Aniline dyes are most commonly found in rugs from Turkey, Afghanistan and Morocco. They are junk! Period. The colours will run and fade and I would not consider purchasing a rug made with them. ‘Nuff said.
Now between chromic and vegetable dyes there are several points to consider. A chromic dye may begin with either synthetic or natural dyestuffs. Chromic refers to the mordant, potassium dichromate. A mordant aids in colourfastness (binding the colour to the wool). Most vegetable dyes also use a mordant, only something found in nature, not a laboratory: common examples include iron, salt, vinegar and even urine (yep, that’s right!). Although there exists a widespread belief that pure vegetable dyes are superior to chromic dyes, it is truly not as simple as that. In fact, some natural dyes are much more fugitive in color or even damaging to the wool than the synthetic dyestuff that yields the equivalent shade.
Moreover, it is usually not possible to neatly categorize carpets as natural or chromic (synthetic or otherwise). Weavers typically use materials that are conveniently at hand, which may mean vegetable reds and chrome-synthetic greens used within the same rug. And to further complicate matters, indigo, one of the best known and most commonly used vegetable dyes, is also made in a synthetic counterpart that is chemically identical to the natural plant dyestuff!
But let’s say we can be certain that a rug is pure vegetable dyes (one way we can be certain is the age; another is the resurgence of vegetable dyeing in some weaving regions). Is this a superior carpet to one made with chromic dyes? Vegetable dyed carpets are associated with more traditional techniques of carpet making. They seem more honest and authentic and impress us with the allure of ancient practices kept alive by modern artisans. This is not inconsequential. The romance of vegetable dyes is compelling. And their beauty is undeniable. Vegetable dyes have a softness and subtlety that only the best chromic dyes can match.
However, bear in mind that the colours in vegetable dyed rugs will patina (fancy way of saying they will change and lighten, at least somewhat) over time. They are also much more likely to abrash (show uneven changes in colour saturation). And some vegetable dyes, such as the black typically used in Balouchi and Turkish rugs can be so corrosive to the wool that we find old rugs in excellent overall condition, but with almost no nap in the dark areas of the pattern.
On the other hand, chrome dyes have the advantage of being extremely colourfast (little or no fading will occur, even over centuries) and a chromic dye will generally colour wool more evenly (with less chance of abrash) and provide a richer, more saturated tone. When made from synthetic dyestuffs, chromic dyes can produce colours not readily found in nature. The result can be some outlandish colours that make the rug garish. Sometimes, however, the wild colours possible with chromic dyes are what make for an interesting rug. We have had some Bidjar carpets from the sixties with turquoise and hot pink and plum in them. A rug like that may not be to everyone’s taste, but when placed in the right room (with steel and white leather, for instance, or super MCM with Danish teak), these rugs look spectacular. And some synthetics replicate vegetable dye colours so convincingly, that without chemical analysis it’s near impossible to tell the source of the dyestuff.
In short, when discussing vegetable or chrome dyed rugs there is nothing inherently better about one or the other though there are pros and cons attached to each. When considering the dyes in a rug, I certainly wouldn’t insist on anything beyond the dyes being of good quality, producing pleasing colours and overall balance in the pattern.
And now, if you’ve ever wondered what vegetable dyes might be used in a rug and how colours are achieved, here is a quick overview.
Common Vegetable Dyes
From a relatively limited range of natural colours, dyers use two techniques, depleted dye baths and double-dyeing, to produce a multitude of colours. When a batch of dye is made, the wool that goes in the bath first absorbs the most intense colour. Subsequent dyeing in the same bath produces weaker shades of the same colour.
Vegetable Dyeing Techniques
By combining colors (or double-dyeing) dyers can produce different hues. There are, for instance, very few vegetable sources for green dyes (most green plants simply cannot be turned into good dyes). However, dyeing wool blue, and then dyeing it again with yellow, will produce a green color. If you look closely at a vegetable-dyed rug, you will commonly see that the color is slightly uneven (a green, for instance, that is more bluish in some sections and yellowish in others). This is because of the double-dyeing technique.
So, by employing depleted dyes and by double-dyeing, dyers can produce a surprisingly large palette of colors.