Can you believe a little worm (more like a caterpillar, actually) is responsible for one of the
most gorgerous fibers out there? Silkworms make a cocoon after they’ve eaten all they can, and as they’re ready to turn into a moth. This cocoon is our silk fiber. Amazing.
Making a fiber and then fabric from the silkworm cocoon started, it is believed, in China about 2600 BC.
As the silkworm begins to prepare its cocoon, it secretes fibroin and rotates as it goes, creating a continuous fiber of about 800 yards. The finished cocoon is about the size of a peanut shell.
The cocoons are gathered, and then stifled (exposed to heat to kill the worm), then soaked to soften the fiber, and unreeled, or unwound, into one long thread.
The most common silkworm is the Bombys Mori, which feeds only on Mulberry leaves. The fiber from their cocoons is Bombyx silk, and is a brilliant white as Mulberry leaves have no tannins which could color the silk.

- bombyx mori silk fiber before spinning
Tussah silk comes from the wild, where the silkworms eat different types of leaves, which do contain tannins. This silk is more ivory or honey colored.
Silk is not a true fiber, in that it isn’t ‘grown.’ It is a protein fluid created by the silkworm, and looks a lot like a long glass rod under the microscope.
There are three types of silk. Reeled silk is the finest. It’s make of continuous silk threads twisted together, but is reserved mostly for industrial uses. Spun silk is the most common type in hand knitting yarns. The thread is cut, carded, and then spun. Noil silk is made of shorter fibers that are left over after the combing and carding. They tend to be irregular, adding texture to the fiber.
Silk is warm, absorbs moisture and releases heat like wool, and is one of the strongest fibers around. Silk takes up dye readily, producing a lustrous, intense color. But, silk has little elasticity and can stretch, and won’t hold its shape well, so would not hold the elasticity in a ribbing. It’s slippery to work with, too. Consider 100% silk for an amazingly fluid and shimmery shawl.
Again, blends are your friends. Add wool and you get the elasticity and memory, plus a gorgeous drape and shine. What about alpaca and silk?