Understanding silk


When you see a label on a garment “100% silk”, what does it tell you?  Other than content, not much about silk grade and type.  If you see something like “Mulberry silk”, is that more information?  Yes, but that only talks about type of silk.  What about “bourette”? This is definitely silk grade, but not type.

The most detailed information about silk yarn will be like this:  Mulberry spun silk 16/2.  Or Tussah spun silk 10/2.  If you’re not a knitter or a weaver, you can ignore the numbers after the yarn grade and type – they deal with the thickness and ply of the yarn.

Now, let’s talk about type.  The most common type of silk is Mulberry, named after the bush that silk warms eat.  Mulberry silk is cultivated, and can be made in three grades:  reeled, spun, and bourette.



The highest grade of the Mulberry silk is reeled silk, coming from the inner part of the cocoon.  This yarn can be twisted or not, but since it consists of long, unbroken, individual cocoon threads, it has the most shine.  It is also very smooth.  If you have a silk scarf that unties itself almost instantly, chances are it is made of reeled silk.



The second best grade of the Mulberry silk is spun silk. It is made of longer threads left after reeled silk is made and of the outer, rougher layers of the cocoon.  Those longer threads are spun and twisted, making a continuous thread.  It also has shine and smoothness, but unlike the reeled silk, it is willing to give a grip to a scarf or a baby wrap.



The final grade of Mulberry is bourette silk.  It is also known as silk noil or tsumugi silk.   It is made of all what’s left after making spun silk.  Result: not very shiny, often rough and nubby thread. But it has the most grip of all the three grades of the Mulberry silk, and it is still silk:  retaining heat in cold weather, cooling in hot weather, not getting soggy, and lightweight.  So, that’s it for the Mulberry grades.


The second most common silk is Tussah.  Named after the silk moth, it is often labeled as “wild silk”, as the cocoons are collected from the wild and not cultivated in workshops.  If the cocoons are gathered after the moth left, then they will be converted into spun silk and bourette silk: after all, the cocoon thread is now broken into many pieces, with the hole that moth made to get out.    I generally find  Tussah spun silk shinier than Mulberry reeled silk or Mulberry spun silk; it is also more slippery, making weaving with it a bit tricky.

If the Tussah silk is referred as “having texture”, the yarn could be of bourette grade.  It is also possible to get reeled Tussah, if the cocoons are processed before moth emerges.  But all in all, Tussah is silk – a strong, light and lovely yarn, like Mulberry silk.

There are other silk varieties, but they are of a novelty and not as widespread as Mulberry or Tussah.

And if you have any questions or comments, feel free to comment here or on my Facebook page.


4 thoughts on “Understanding silk

  1. Great article, thanks!
    If speaking of “animal friendly silk” would you refer to tussah silk if the cocoons were collected after the worm transformed into moth? Are there other varieties of silk where the cocoons are collected only after the worms leaves it, like Eri Silk for example?


    1. Hi Regina, thank you for your comment. I did not look deeply into available animal-friendly silks, but, as you pointed, tussah silk cocoons collected after the silk worms pupated, are animal friendly. All I have to say that reeled silk is not animal-friendly as the technique to make it requires an intact cocoon.


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