> Actually, I believe cotton dyes quite easily. It is on linen that most (natural) dyes
> don't take.
Trying to dye cotton is as difficult as trying to dye linen, as both are cellulose fibers and they don't take most natural dyes.
They can be colored, but the dye will not be fast and will fade and/or wash out. This is not considered desirable. Also, the color tends to be rather pale, also not a desirable trait within SCA-period.
Both can be readily dyed with indigo, which is a vat dye and does not require a mordant. Any other dyes are much more difficult, if not nearly impossible to reach a saturated intense color. Madder is one of the few, but there are tricks to dyeing cotton and linen with madder, which Europeans didn't know until after the end of SCA-period, but which were used in the Middle East.
Modernly cotton does dye well with FIBER REACTIVE DYES, as do linen, rayon, hemp, ramie, bamboo, and nettle. Procion dyes were the first readily available fiber reactive dye and they were introduced in 1956, well out of SCA-period. Fiber reactive dyes do not require mordants and dye in cold water, and are light fast and color fast (i.e., don't wash out). They often need a base added to make the water alkaline.
I have limited experience dyeing (i took two dyeing classes in university) -- with natural dyes and with the mordants alum, tin, and chrome on a range of fibers/fabrics including cotton. Also with modern chemical indigo, with acid dyes (bubble bubble toil and trouble), and with Procion dyes. I prefer natural dyes, but while they work well on protein fibers -- wool and silk -- they don't work well on cellulose fibers -- linen and cotton.
Urtatim (that's oor-tah-TEEM)
the persona formerly known as Anahita