Rowen here, filling in a bit (yes, I borrowed the sign-on.)
More specifically, what fibers were Gwernin's people using to make cloth & clothing? And where were they getting them? Archaeological evidence for 6th c Britain gives us two main fibers, wool and linen, and very, very rare bits of silk. Just now I'm going to talk a bit about wool.
Woolen fabric, for the most part, would have been locally produced, and a great deal of it worn in "sheeps'-color", i.e. the shades of the natural fleeces. This does not mean that folk would have all been wearing the same light grey-brown; sheep that have not been specially bred for *white* fleeces can produce a wide range of cream, charcoal, pale grey, russet, or rich brown wool. Wealthy folk, however, would have had specially-dyed, possibly imported, fabrics for their better garments. (Wealthier folk would also have had more than one or two sets of clothing, as well, but the idea of a new outfit for every occasion is quite a modern one!)
In addition to dyed or natural colors, garments could have been – and were – decorated with stitchery or embroidery, contrasting bands of fabric or tablet-weaving at the neck and sleeves, or enhanced by the pattern of the weaving: a broken twill or herringbone, or diamond-twill pattern took more time and skill on the part of the weaver than a simple tabby (basic over/under) weave. Deep, rich colors were more time-intensive to dye, and might call for (expensive) imported ingredients. The easiest and most common local dyes produced a range of yellow/gold, brown, and greenish shades, but some herbs and lichens could produce astonishing purple, cerise and orange tones.
Modern taste often leans toward the irregular weave or dye-lot as looking “more hand-made,” but in a world where every single thread of every single piece of fabric – a queen’s coronation gown, an infant’s swaddling bands, sails for ships or sheets for beds – had first to be spun on a drop-spindle before it could be woven, the smoother thread and the even weave or dye-job were a sign of greater skill, and produced an object of higher status.
Next time: some thoughts on linen.