Hey guys, I’m back! Sorry about the long delay, I had a long but fun weekend with a few friends visiting me all the way from Toronto. A few drinks at the bar was enough for me to forget a lot of things. I did write up some stuff last night but it was late and my writing was barely coherent so I thought I might as well do it later when I can think straight, which, as it happens, is now.
Well let’s end my poor attempts at finding excuses and get on with it. Today I’m going to talk about the nature of silk and how it affects the way we utilize silk. Before I start, let me give you a bit of fair warning, as today’s article might seem a bit too technical for how I usually write. My suggestion is, don’t let it bother you. If you are curious about a particular term, look it up in google or Wikipedia, or ask me in the comments, I’ll explain them as best as I can.
So, before we go any further, the first questions we gotta ask ourselves is: What is silk?
Silk can refer to both natural protein fibers extracted from the cocoons of the silkworms of a number of insect species, or the textile woven from these natural fibers. Generally speaking, when I talk about high end silk products on the market such as pillowcases or duvet covers, I’m referring to the silk made from the cocoons of the Bombyx mori moth, which grew up eating Mulberry leaves. This silk is thus called “Mulberry silk” and is of the highest grade as the production process has evolved for thousands of years and become very mature.
Now that we know what silk is, the second question is: What is silk made of?
Silk is mostly made up of two proteins, called sericin and fibroin. These two protein make up for about 90%-95% of silk, with the rest being carbohydrates, wax matter and other inorganic substances. Fibroins are what makes up the “silk” as we know it, as they form the long strings of silk fiber that act as the structure of the cocoons. Sericin, on the other hand, is the “glue” with which the silkworms hold the fibers together in the shape of the cocoon. Large amounts of sericin is irritant to our skin, so after pupa have been removed, the cocoons must undergo a process in which they are placed in water and lose most of the sericin coating. The filaments made of fibroins are then drawn from the cocoon and weaved, eventually made into silk fabrics as we know it.
So what makes silk special? Let’s first take a look at some of the properties of fibroin and sericin, the major components of silk:
Fibroin is a protein made from glysine, alanine and serine, all three being amino acids that exist in the human body. Physically, fibroin is thin, long, lightweight, and very soft. Fibroin is known for its:
– Water absorbency: The chemical structure of the fibroin molecule makes it very good at capturing free water molecules. Note that this might sound contradictory with what I said in my previous articles about silk having low absorbency – the way silk absorbs and stores water is different with how cotton does it, and silk does absorb a lot less water than cotton of the same mass when drenched.
– Thermal tolerance: Fibroin is fairly tolerant to heat, with very little shape and mass change when heated up to 80C/176F. (Fibroin is NOT silk fabric, so don’t try this with your silk pillowcases, it will change shape due to other reasons!)
– Insulation: Fibroin is a good heat insulator as it is a poor conductor for heat. The way it keeps heat is different from down/cotton which does so by trapping large pockets of air.
– Luster: The natural luster of silk comes from the way fibroin strands reflect and refract light.
Sericin is the glue with which silkworms hold the fibroins together to make the cocoon. Most of sericin is removed before processing fibroin strands into usable silk threads, but a certain amount sericin is left in processed silk, giving it the unique “silk smell” that people often mistake for chemicals. As the “outer layer” of silkworm cocoons, Sericin possesses some unique protective properties which are capable of fending off potential harmful effects that could prevent the maturing of pupa:
– Anti-bacterial: Sericin has a very strong anti-bacterial property. Experiments have been conducted in which different bacteria colonies were placed on silk swatches with different levels of sericin and placed in a controlled environment that imitated a well-circulated bedroom. The colonies that were placed on the silk swatches with the most sericin content died out faster than the rest.
– UV-Resistant: Experiments have shown that sericin is able to absorb a part of any UV radiation it receives and thus offers a certain level of protection against UV.
– Anti-Oxidant: Research has shown sericin has good anti-oxidant capabilities. In fact some companies have already made health supplements from sericin and anti-oxidation is one of the biggest selling points.
– Tyrosine-Inhibitory: You may not be familiar with tyrosine. Tyrosine is an amino acid that is used by your body to produce melanin, the pigment that makes moles black. Contact with sericin could prevent melanin from forming and keeping dark spots away from your skin.
As you can see, many of these properties of fibroin and sericin are very beneficial to our skin and hair; but when they combine into silk fibers, there are even more advantages. Unfortunately, it’s getting really late today so I’m going to have to stop. I’ll finish this piece first thing I come back from work tomorrow, so stay tuned!