Silk Fiber

It's amazing that silkworms have produced the silk fiber used to cloth royalty for centuries. Insects are often regarded as lowly and disgusting, but not this worm!

Properties

Silk fiber is known for its high luster. It shimmers, but it is not slippery and good for drop spindle spinning. Silk is very strong when reeled because the fibroin is spit by the worm in one long strand between 275 and 1640 yards (250 and 1500 meters). There are 1760 yards in a mile.

I got to babysit these 17 Bombyx mori silkworms
that are about halfway through the growth cycle.

It's a strong fiber but weaker when damp. Silk is also weakened by the sun.

It's absorbent gut resistant to mold and rotting. It doesn't have any elasticity, so blend it with wool if you need a little stretch. It's good for lace patterns because it holds the blocking.

Silk is the only type of animal fiber resistant to the wool moth, but it's still vulnerable to the carpet beetle.

It's warm and soft with a nice drape. Most people are surprised at how warm silk can be because we associate it with hot climates, but nights can be very cold in the desert or up in the mountains. You often see silk used to make thermal underwear.

Production

Most silk is produced by sericulture of the mulberry silkworm as described on the Wormspit website. There are three types of fiber available for silk spinning:

Bombyx mori

This domesticated insect only survives in captivity and feeds on mulberry leaves. The mulberry silk is very white. It can be reeled off the cocoon in one long strand, which involves a dead moth, or the moth can emerge so that the strands are cut and have a golden stain, but that can be bleached out.

Tussah

This is a type of semi-domesticated silkworm that feeds on oak. The tussah silk has a more golden color.

Silk noil

These are the knots and neps left after combing and carding. Blend it with other fibers to add texture to yarns. Sometimes it has an odor but that can be washed out.

For the best silk, the cocoons undergo stifling to kill the moth with heat or steam. You end up with a dead moth inside, but the silk is in one continuous long strand that can be reeled. Soak the cocoons in hot water to degum them and find the strand ends. Reel a couple of strands together. You can add some twist by using a croissure as you reel.

If the silkworms are left to mature and hatch as moths, they will break strands to emerge from the cocoon. The silk strands turn brownish at that spot. It is still useable, but not as strong. This type of silk is called peace silk or ahimsa silk. Ahimsa is a Sanskrit word meaning "a reverence for life".

All cocoons must be degummed in hot water to remove the sericin glue holding them together. They can then be reeled or stretched on a little frame to create silk hankies or mawata for spinning silk yarn.

Silk requires 50% more dye than wool to get the same level of color saturation, but it never fades and looks great.

Recommended Reading

These books will tell you about the marvelous wonders of silk and give you some silk patterns.