Silk

The Atlas moth secretes broken strands of silk that are very strong. The discarded cocoons are used as purses in Taiwan. (Image courtesy woodleywonderworks via Flickr)

Unlike the Bombyx mori, the Atlas moth secretes broken strands of silk. The discarded cocoons are sometimes used as purses in Taiwan. (Image courtesy woodleywonderworks via Flickr)

Soft and smooth to the touch, with a luster associated with luxury, silk is also one of the most enduring natural materials out there. It is stronger than steel and more flexible than nylon. With the exception of a few runs and snares, silks dating back to the 3rd and 5th century C.E. still look pretty good for being 1,500 years old.

Silk has long been revered for its complex cultivation, known as sericulture, from the Bombyx mori moth. Newly hatched at just a few millimeters long, Bombyx mori caterpillars (colloquially known as the “silkworm”) feed ravenously on mulberry leaves and, in the span of two-three weeks, grow exponentially to about two inches long. Following this feeding frenzy, they secrete a stream of protein saliva that hardens on exposure to air, and within about 36 hours, the caterpillars are snuggly enveloped in a silky cocoon. Unraveled, a cocoon provides a single silk thread that can be as long as anywhere from 900-3,000 feet. About 2,000-3,000 cocoons are needed to yield one pound of silk.

Woman in silk factory in Vietnam, 2008. (Image courtesy Francesco Paroni Sterbini via Flickr)

A silk factory near Dalat, Vietnam, 2008. (Image courtesy Francesco Paroni Sterbini via Flickr)

The discovery of silk fibers dates back to around 3,000 B.C.E. and is credited to Xi Ling Shi, the wife of the Yellow Emperor – often referred to as the founding father of Chinese culture. According to legend, Xi was sipping tea under the mulberry trees when a cocoon fell into her beverage. She watched in amazement as the silk fiber of the cocoon unraveled and shimmered in her teacup.

Just as wool comes in many forms, from shearling to cashmere, there are many grades and types of silk, according to region. Chinese raw silk, for example, is typically white, while Thai filaments are a vivid turmeric yellow. Silk fabrics are measured by the density of their weave using momme, pronounced “mommy” and abbreviated as mm. Silk under 20 mm is lightweight, 20-28 mm mid-weight, and 28mm and above heavyweight.

Woman holding silk cocoon. (Image courtesy via Francesco Paroni Sterbini Flickr)

A silk cocoon in Vietnam. (Image courtesy via Francesco Paroni Sterbini Flickr)

Here’s a cheat sheet:

Chiffon is one of the lightest silks available. With a measure of 6-8mm, it is sheer and billowy.

China silk, also called habotai, habutai or “washable silk,” can be anywhere from 5-18mm. Most traditional kimonos are made from this material.

Charmeuse is the most common type of silk and recognizable by its double-sided weave: one side of the fabric is flat and matte, while the other side has a shiny luster. Its momme measure ranges from 12-20.

Silk jacquard is a heavyweight fabric, and often used for jackets and coats or curtains and tablecloths.

Tussar silk, also termed shantung, tussah or kosa, is woven from the pale gold cocoons of South Asian wild tussah silk worms that feast on oak and juniper leaves instead of mulberry. If the worm isn’t grown in a controlled sericulture environment, the moth hatches from the cocoon to create many short and coarse fibers, instead of one long silken strand. The cocoons can also be heated in the sun to prevent the moth being expulsed and the silk breaking.

Vegans, Buddhist monks and other animal-lovers look for eri or “peace silk” when purchasing their garments. This type of silk is made by the Samia cynthia ricini or Eri caterpillar, which can burst unharmed from its cocoon. Like wild tussar silk, the fibers are short and coarse, as well as dense, elastic and warm. What can’t the mighty silkworm do?

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