Friday, July 12, 2013

Fiber Feature - Silk


Silk is the fiber I'll be talking about today.  I've chosen silk because it is a unique fiber that bridges the gap between plant and animal fibers and this is where I find myself in these brief descriptions of fibers.

Silk has been used to produce fabrics for thousands of years. China was one of the earliest commercial producers and the fabrics they produced were in great demand throughout the known world.  Most of you will be familiar with the ancient trade routes that connected China, Southeast Asia, the Middle East, the Mediterranean and the Indian subcontinent, called the "Silk Road."  If you ever get the chance to watch some of the history documentaries about the silk road you will be amazed at how much this fiber has played a role in world politics and trade!  There are still many incredible archeological discoveries being made along the ancient route.

Silks are naturally occurring protein polymers that are produced by many different kinds of insects and spiders. I found a great plain language article about Natural Polymers if you want to read more. Each species of silk producing creatures makes a silk with slightly different characteristics. The silks most commonly used by humans to produce fabrics come from only a couple of kinds of moth caterpillars known as silkworms.  Silkworms eat plants and during the course of their short lives produce and accumulate two natural polymers called fibrion, which forms the core of the silk and sericin which coats the fibrion and makes it sticky.  When the time comes they secrete these stored fluids which harden upon exposure to the air, forming cocoons in which to pupate.  I enjoyed this Youtube video: Sericulture -Life Cycle of  Silkworm.

Cultivated silk, called bombyx silk, comes from the Mulberry Silkworm, Bombyx mori.  It is especially bred to have the whitest and finest silk without the mineral accumulations that wild silkworm silks have. This species feeds only on mulberry leaves which contain no tannins that could ting the silk brown.



The other commonly seen silk is Tussah Silk which comes from wild or simicultivated varieties of silkworms which feed on different plants.  Many of the other plants contain tannins which can give the silk colors ranging from ivory to honey brown.

Silk is incredibly strong "pound for pound silk is stronger and less brittle than steel" says an article in ScienceDaily.  Several other sources concur, although it does lose up to 20% of it's strength when wet.  Silk is also not very elastic so when stretched it may not return to its original un-stretched shape. It is susceptible to damaged from too much sunlight and can be attacked by insects, especially when left dirty.  What this means for handcrafters is, be gentle when laundering silk, dry clean when possible, and don't leave in the sun to dry. Silk can absorb and release moisture making it comfortable on the skin and feels warm against the skin.  This makes it very nice for cold weather garments when wool is undesirable.

The physical structure of silk is such that there are many flat micro structures that reflect light in many different directions, giving silk it's brilliant shine.

There are two different kinds of silk that come from the same cocoon, the outer silk which is rougher and darker, which we know as raw silk. Shibui Heichi is a lovely example of raw silk yarn.  Then there is the fine silk from the inner cocoon.

Of the finer silk there are three grades;

Reeled silk is obtained by unwinding the silk in one long filament from the cocoon after it is boiled to remove the sericin.  (Yes, silkworms are killed in this process, which some take a dim view of. In most major silk producing countries these worms are used as a food source for humans. I'll leave the ethics of silk production aside for this discussion.)

Spun silk is made from either the waste from the reeling process, the inner casing, and/or from cocoons that were pierced by the moth as it was allowed to emerge naturally. One source said that 20% of the moths are allowed to emerge to lay eggs for the next generation.  This silk is cut into standard lengths then carded in preparation for spinning into yarn.

Noil silk is the left over and waste from carding & combing spun silk.  Silk noils are used to add textures and when dyed to add flecks of color to yarns, such as Rowan Summer Tweed & Plymouth Mushishi.  They can also be added to tweeds.

Knitting with silk is a little different from other fibers because of it's smooth, slippery, and fluid quality.  It can get away from you quickly.  If you usually knit on slick needles you may want to try less slippery needles or a size or two smaller than called for to keep your silk well managed. When laundering your silk, follow the yarn label instructions carefully.  If the label says to dry clean only do as it says.  Washing some silks in water can dull the sheen and cause the dye to fade or blotch.  Most hand knitting silk yarns can be hand washed though.  Do be careful as silk will felt so follow the same procedures as wool.

Choose silk when you want lots of drape in your project, it's not the best choice when you need a lot of bounce.  If you need more elasticity/stretch then choose your silk blended with a more resilient fiber like wool.  Some people find that silks catch on every little flaw in their skin, making it unpleasant to touch. If this is a problem for you, a trick that hand spinners use is to rub fresh lemon juice on your fingers while you working with it.  If that still doesn't help try sticking with Tussah silk as it's not as fine and may not catch.  Regularly using your Bar Maids Lo Lo bars will help too.  Be sure to apply while your hands are damp to seal in the most moisture then reapply as needed.

We have a few 100% silk yarns at the moment.  One of the most luscious is Debbie Bliss Luxury Silk DK and Luxury Silk Print then there are Artyarns Beaded Pearl, Beaded Pearl & Sequins, Beaded Silk Light, Silk Pearl, and Regal Silk. We also have many silk blends so check out our Advanced Yarn Search for silk and find some of my favorites like Rowan Kidsilk Haze, Cascade Heritage Silk, Noro Taiyo Sock, Shibui Staccato, Hand Maiden Sea Silk, Shibui Silk Cloud and many others! Silk Search.

I hope I didn't put you to sleep again!  As alway I hope you find this helpful and if you have further questions drop me an email at askTerry at jimmybeanswool dot com.

Terry

4 comments:

  1. Fascinating!! I've loved the series of posts about the various fibers. Well done!

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  2. i loved reading this! it was very interesting!

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  3. It's always great to learn more about the fibers we can knit with! Perhaps you could link your "silk" topic to some pattern suggestions for sweaters and tops.

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  4. Thank you all for you comments! Sophy0075, what a great idea! I'll post some pattern idea tomorrow.

    Terry

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