The Univoltine breed is generally associated with a geographical area in Greater Europe. Due to the cold climate, eggs of this species overwinter in winter and are not fertilized until spring, producing silk only once a year.
The second type is called a bivolt and is typically found in China, Japan and Korea.The reproductive process of this species occurs twice a year, made possible by the slightly warmer climate and the resulting two life cycles.
Eggs are laid by female moths and hatch in 9 to 12 days, so the resulting type can have up to eight different life cycles per year.
Silkworm breeding aims to increase the overall improvement of silkworms from a commercial point of view.The main goals are to improve fertility (a breed’s ability to lay eggs), larval health, the amount of cocoon and silk production, and disease resistance.
Health depends on factors such as better pupation rate, fewer dead larvae in the cluster, shorter larval lifespan (shorter larval lifespan reduces the risk of infection), and bluish fifth-instar larvae (which are healthier than reddish-brown). .
The amount of cocoon and silk produced is directly related to pupation rate and larval weight. Healthier larvae have higher pupal rates and larger cocoon weights.The quality of the cocoon and silk depends on several factors, including genetics.
The adult possesses rudimentary mouthparts and doesn’t eat during the short period of its mature actuality. The bitsy eggs of the silkworm moth are incubated( about 10 days) until they door into naiads ( caterpillars). At this point, the naiad is about a quarter of an inch long.
The periphery of the spinneret determines the consistence of the silk thread, which is produced as a long, nonstop hair. The concealment harden on exposure to the air and form binary fibers composed of fibroin, a protein material. The alternate brace of glands secretes a sticky list fluid called sericin which bonds the two fibers together. Steadily over the coming four days, the silkworm rotates its body in a figure- 8 movement some,000 times, constructing a cocoon and producing about a kilometer of silk hair. If the beast survives after spinning its cocoon and through the pupal phase of its lifecycle it releases proteolytic enzymes to make a hole in the cocoon so it can crop as an adult moth. These enzymes are destructive to the silk and beget the silk filaments to break down over a afar in length to parts of arbitrary length which seriously reduces the value of the silk vestments. To help this, silkworm cocoons are boiled.
The silk is then released from the cocoon by softening the sericin and then gently and carefully unwinding or “rolling up” the fibers. Folding can be done manually or automatically. The cocoon is brushed to locate the fiber end. It is threaded through a porcelain eyelet and the fiber wrapped around a wheel. When each strand is almost ready to be wound, a new strand is wound on top of it, creating one long, continuous strand.
To make weighted silk, metallic substances are added to the fabric during the dyeing process to increase weight loss during degumming and add density to the fabric.
Improper weighing can shorten the life of the fabric, which is why silk in its pure form is considered a very high quality product. After dyeing, silk fabrics can be finished with other processes such as bleaching, embossing, steaming or stiffening.
The next step would be to create the ideal environment for rearing silkworms.There are several ways to breed silkworms. Typically, farmers put shelves in the building and place silkworm beds or trays on top where the silkworms will grow and feed. However, some farmers prefer to breed silkworms in special containers or aluminum boxes.
When everything is ready to raise the silkworms, it’s time to buy eggs or lay silkworms (usually on specially prepared paper). The eggs will hatch and you can start feeding them mulberry leaves.Make sure your silkworms stay warm and dry with good ventilation or they will suffocate and die. If you choose to grow silkworms in containers, it is best to keep the temperature between 30° and 30°C and make sure that no condensation or waste is left in the container.
After about 35 days and 4 molts, the silkworms are ready to form a cocoon. Place a straw frame on each silkworm dish to allow the silkworms to start spinning their cocoons.
Then the silk farmers heat the cocoons to kill the silkworms. Some farmers leave a small proportion of silkworms alive so they can turn into moths and raise the next generation of silkworms.
The collected cocoons are then immersed in boiling water to soften the sericin that holds the silk fibers together to form the cocoon. The fibers are then unwound to form a continuous filament. Because a single thread is too fine and brittle for commercial use, three to ten threads are spun together into a single silk thread.
The raw silk is spun into thread strong enough for knitting or weaving. This process of creating the silk thread is called “casting” and prevents the thread from splitting into its constituent parts. This method can be used to produce four different types of silk threads: crepe, tram, throw and organzine. Crepe
is made by twisting single threads of raw silk, doubling two or more of them together, and then twisting them again. It is usually used to weave pleated fabrics.
Tram is made by twisting two or more wires in one direction only. It is usually used as a fabric or filler.
Thrown Singles are single strands twisted in one direction only. It is usually used for transparent fabrics.
Organzine is a thread made by twisting raw silk first in one direction and then twisting two threads in opposite directions. It is usually used for the warp threads of materials.
Broken or missing filaments and damaged cocoons are preserved, treated to remove sericin and combed. It is then processed into yarn that is marketed as spun silk, which is essentially inferior to the rolled product and much cheaper.