Sericulture

Sericulture is the process of raising silk moths and then harvesting their cocoons in order to obtain silk fiber. Many species of moth spin cocoons that can be used for silk, but the two most common are Bombyx mori, whose cocoons make bombyx silk, and the tussah moth, which produces tussah silk. Bombyx eggs need to hibernate, so the bombyx moth normally produces only one crop of eggs a year (although there is now a chemical process to induce a second hatching). The tussah moth, on the other hand, can produce up to seven "crops" of eggs a year.

Each silk-producing moth eats a different kind of leaf, which explains why silk can have different characteristics. For example, bombyx moths eat leaves from the white mulberry tree, so their cocoons, and therefore their silk, tend to be very light colored-almost white. Tussah moths eat oak leaves, which contain tannin, so their cocoons have more color.

Most tussah silk is gold, although it can also be green or tan. But tussah silk for handspinning is also available bleached, which can make look very much like the more expensive bombyx. Tussah, however, does not feel quite the same as bombyx, because it's slightly coarser.

1. The eggs are kept in hibernation until the mulberry leaves sprout.
2. Then they Are allowed to hatch, and the larvae immediately begin feeding voraciously on the leaves.
3. They shed their SKIN four times during this stage, eating increasing amounts of leaves as they grow. It has been estimated that the total weight of leaves needed for just 1/10 of an ounce of eggs is about 45 pounds.
4. After the last shedding the larvae will increase their feeding almost exponentially. It may take up to 180 pounds of leaves for this same amount of eggs-and larvae-to make cocoons which will eventually produce about a pound of usable silk fiber.
5. After four to five weeks of doing nothing but eating, the larvae spin their cocoons from fiber (made from all the leaves they have been ingesting) mixed with a kind of sticky saliva that holds the fibers together and also attaches the cocoons to a leaf or some other part of their housing. It takes about three days for the cocoons to be spun.
6. The cocoon stage lasts about 10 days, at the end of which the adult moths normally hatch, mate, and lay their eggs.
   
7. But if the cocoons are to be used for silk, the moths are killed before they emerge so that the integrity of the cocoon is not disturbed.
   
8. The cocoon was originally spun with one continuous length of filament, and if the moth breaks through the filament will be broken, which would make the next stage of the process more difficult and produce a lower grade of fiber.
9. The reeling of silk is actually not a complicated process-in theory. The cocoons are put into a container of hot water and allowed to float freely until the gum which holds the silk fibers together is softened.
   
10. Then the beginning of the filament is located and, held together with the filaments from many other cocoons, attached to a reel, which is turned slowly as the silk filament unwinds from the cocoons.
    
11. Once all the silk fiber has been reeled it is tied together and degummed, dyed, or otherwise processed into fiber for spinning, either by hand or machine, into thread.
12. It is also possible for the cocoons to be saved and processed differently at a later date. For example, handspinners can obtain silk cap, the fiber from several cocoons which have not been reeled but instead have been degummed and stretched.
    
    
    It takes about 1,400 cocoons to make just one pound of silk-which is probably one of the reasons why silk is so expensive. There are alternatives being developed, including fibers from soy and from corn which are also called "silk." These have the advantage of being cheaper to produce, and may be a good choice for people who are bothered by the destruction of the moths. How successful they will be in replacing the original remains to be seen. Silk was the first luxury fiber, and many people still prefer it for that reason.