Silk is one of those luxury fibres that I have always wanted to work with but which I haven’t really managed to do mostly because of budgeting criteria I have for my knitting. Luckily there are a lot of silk blends that might make a smaller item affordable to me. Before going into more detail about the fibre I just want to mention that silk is not an animal friendly fibre as the larvae are killed in the process and for me this means this fibre should be used sparingly or try to use recycled silk fibres.
Silk is another fibre that has been used for thousands of years. It originated in China and legend has it that it was discovered by an empress how was having tea under a mulberry tree when a cocoon fell into her cup and begun unravelling. It is said she was fascinated by the fibre so much that she soon begun cultivating it. Regardless of the truth of the legend, China had the monopoly on silk production for centuries by keeping the production secret under threat of death. Silk was a popular luxury product that spread West through the Silk Road and eventually the production method also reached the West.
How silk is made
Cultivation of the silkworm is known as sericulture and the first step in the commercial production is to lay silkworm eggs in a controlled environment. Each female moth is able to lay 300-400 eggs at a time but dies nearly immediately after depositing the eggs, followed shortly by the males.
It takes approx. 10 days for the eggs to hatch into larvae which are about 1/4 inch long at that point. Now the larvae are placed under a fine layer of gauze and fed copious amounts of mulberry leaves, roughly 50,000 times their own weight in plant material. They eat almost continually for 6 weeks and during this time shed their skin about 4 times. In that time they can grow to up to 3 inches and are ready to spin a silk cocoon after this.
The silkworm attaches itself to a frame, twig, tree or shrub for this process. The process of spinning a silk cocoon takes anything between 3 and 8 days. The silkworms possess a salivary glands which produce fibroin and clear fluid that is forced through spinnerets which are openings on the mouth of the larvae. The liquid secretions harden when exposed to air and form twin filaments of fibroin. Another gland secrets a gummy binding fluid called sericin which bonds the two filaments of fibroin together.
To build the cocoon the silkworm rotates in a figure 8 movement up to 300,000 times and produces about a kilometre of silk filament in the process.
Afterwards, the cocoon is treated with hot air, steam or boiling water which kills the larvae but also the sericin to soften and for the filaments unwind. This is usually done with 4-8 cocoons at once which are twisted together lightly to create a single strand.
The sericin is usually left in the yarn as it protects the fibre during the processing but it washes out easily which soap. Before washing it out the sericin the silk is labelled raw silk.
The stands are twisted together into yarn for weaving or knitting which prevents a thread from splitting into its constituent fibres. Depending on how the fibres are spun they have different qualities. Crepe is made by twisting individual threads, doubling two or more and then twisting them again. Tram is made by twisting two ore more threads into only one direction. Thrown are individual threads twisted in one direction only and Organzine is made by giving the silk a preliminary twist in one direction and then twisting two of these together in the opposite direction.
In general, organzine thread is used for the warp threads of materials, tram threads for the weft or filling, crepe thread for weaving crinkly fabrics and a single thread for sheer fabrics. All can be used for knitting.
Pro and Con
Silk is a very durable fibre and has a beautiful sheen and drape. The texture is smooth and soft. Silk has good absorbency which makes it comfortable to wear in lovely weather and has also the capability to prevent insects from biting through the fabric.
A real negative aspect of producing silk is that the larvae are killed in the process. It is not an animal friendly production and if this is a concern for you than silk might not be the fibre for you. However, there are quite a few artificial fibres that imitate silk if you still like to use something with a similar appearance and feel, for example: rayon.
Silk and Silk blends
As I said I have not used silk so all my suggestions are based on recommendation or is yarn from companies I have used/heard good things of.
Rowan Kidsilk Haze (mohair and silk blend)
Blue Sky Fibre Alpaca Silk (alpaca and silk blend)
Shibui Knits Staccato (merino and silk blend)
Quince and Co Tern (wool and silk blend)
Linen pattern ideas
There are some amazingly beautiful knitting patterns using silk yarn or blends out there. Here is a selection of some of my favourites: