Silk is produced by unraveling silkworm cocoons, after they have been heated in water to loosen the sticky sericin that holds the cocoon together. Equipment for this is known in Italy during the medieval period. The individual filaments would be plied together, with the fineness of the thread depending on how many were joined.
It seems there was no silk cloth weaving industry in England at this time though there may have been some tablet weaving of narrow wares there. Most silk was imported as cloth from Italy and points east, via Italy and other Mediterranean countries.
A number of Tabby woven silk cloths were uncovered in London, many of which were used for facings or linings. The ones used as facings were often un-dyed, and were a light brownish colour. Because these examples were cut into small pieces it is difficult to determine how wide the original cloth was. However, regulations on the weavers in Italy stipulate that taffeta, a tabby woven textile, was to be woven a specific number of "braccia" wide (resulting in 109-118 cm wide cloth). Many of the tabbies are reasonably well balanced with a warp and weft count between 30 and 40 per cm. Taffetas could be woven with warp and weft of a different colour, since silk was often dyed before it was woven.