What are the different types, grades and qualities of silk yarn?

Thai silk has explicitly defined types, grades and qualities.

Thai Agricultural Standard TAS 8000-2005 – Thai Silk Yarn defines the following types of silk yarn:

  • Mai 1 or Mai Noi or Mai Kreu is the silk yarn reeled from the inner layers of the cocoon.
  • Mai 2 or Mai Sao Loei is the silk yarn reeled from a combination of the inner and outer layers of the cocoon.
  • Mai 3 or Mai Leub or Mai Laeng is the silk yarn reeled from the outer layer of the cocoon with the addition of the floss from the innermost layer.

The standard further defines the qualities of the types of yarns:

  • Mai 1 silk yarn is even in structure, size and colour, round, clean and free from adulterated materials. This grade is sub-divided based on testable characteristics into three quality levels: Premium grade, First level grade and Second level grade. The sericin level is ≤ 30%.
  • Mai 2 silk yarn is not even in structure, but is even in size and colour, round, clean and free from adulterated materials. This grade is sub-divided based on testable characteristics into two quality levels: First level grade and Second level grade. The sericin level is ≤ 30%.
  • Mai 3 silk yarn may contain some knots. It is round, even in size and colour, clean and free from adulterated materials. This grade is sub-divided based on testable characteristics into two quality levels: First level grade and Second level grade. The sericin level is ≤ 40%.

The standard also defines the acceptable tolerances of the yarn for the quality specifications above as follows:

  • Premium Grade – Not more than 5% deviation from the criteria set for Premium Grade quality, and at least meeting those of First level grade.
  • First Level Grade – Not more than 10% deviation from the criteria set for First Level Grade quality, and at least meeting those of Second level grade.
  • Second Level Grade – Not more than 10% deviation from the criteria set for Second Level Grade quality.

The highest possible quality Thai silk is type Mai 1 of Premium Grade quality.

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