Bamboozled: A Fiber Facts Update

Apparently, bamboo does not necessarily make something eco-friendly. According to the Federal Trade Commission, bamboo textiles are simply another type of rayon, made using the same process. As I showed in my Fiber Facts post on rayon, the process involves harsh chemicals that are anything but eco-friendly. No matter what fiber you start with, rayon is a classed as a [hu]man-made fiber.

Now, the FTC is taking action, warning companies (including Amazon, Target, and Macy's) that they must change their labeling of "bamboo" fabrics to "rayon." While the FTC does not seem to have targeted yarn manufacturers in their efforts, presumably the same implications would apply. If your yarn label says bamboo, it probably means "rayon." The same goes, presumably, for yarns made out of corn or hemp.

The FTC has a useful guide here, if you want to know more. Interestingly, the clothing & textile regulations do not seem to apply to yarn--from what I can find.

Fiber Facts: Viscose (aka Rayon)

Viscose, or rayon, was first developed in 1855, by George Audemars. Commercial production didn’t begin until 1891, and wasn’t practicable until 1894, when Charles Frederick Cross, Edward John Bevan, and Clayton Beadle determined that treating plant fibers (cellulose) with carbon disulphide created a viscous liquid (they called viscose) that could be spun into filaments and then woven into fabric or spun into yarn; it was the spun textile that was called rayon. In Europe, the terms “viscose” and “rayon” are used interchangeably to refer to the yarn/textile.
In brief, the process begins with plant fibers—wood pulp, bamboo, or the like. In the case of wood, the pulp is boiled and treated with chemicals, then kneaded into “crumbs.” These crumbs are churned with carbon disuplhide, which is how they turn into the viscous liquid called viscose. This liquid can then be stun into staple fibers. Here’s a visual overview of the process, courtesy of ExplorePAHistory.com.


Here’s an image of viscose staple fiber:

The staple fiber can then be woven into fabric or yarn. For more on the process of rayon production, check out this great website.
Rayon became popular as a textile in the 1920s:

(Courtesy of ExplorePAhistory.com)
As environmental concerns become increasingly important for knitters, we are likely to see even more yarns made from plant fibers—bamboo, wood pulp, corn, hemp, and the like. Cellulose-based fibers familiar to knitters include bamboo, viscose, rayon, and the trade names Tencel and Modal. While they tend to stretch out more than some other fibers, their advantages are many. Cellulose fibers tend to be lustrous, smooth, cool and comfortable, making them ideal for summer and spring-weight sweaters. But are these fibers really as environmentally friendly as we think?
On the one hand, plant fibers are renewable resources. The fibers used for yarns tend to grow quickly.
Yet, the production process for rayon and other plant fiber still entails some environmental damage. Most rayon factories treat cellulose with chemicals including sulhpuric acid, carbone disulphide, chlorine, and/or caustic soda. The carbon disulphide used in the process released into the environment as a gas. (1)  According to the Government of Australia, the effects of high exposure to carbon disulphide include:

Acute effects: At very high levels, carbon disulfide may be life-threatening because of its effects on the nervous system or heart. Exposure can be through inhalation, absorption through the skin, ingestion, or skin or eye contact. In acute poisoning, early excitation of the central nervous system resembling alcoholic intoxication occurs, followed by depression, stupor, restlessness, unconsciousness, and possible death. If recovery occurs, narcosis, nausea, vomiting, and headache can occur.
Chronic effects: In chronic poisoning, there are sensory changes such as a crawling sensation in the skin, sensations of heaviness and coldness, and "veiling" of objects so that they appear indistinct. Exposure can cause changes in breathing, chest pains, muscle pain, weakness, loss of feeling in the hands or feet, eye problems, skin blisters, chronic fatigue, loss of memory, personality changes, irritability, dizziness, anorexia, weight loss, psychosis, polyneuropathy, gastritis, kidney and liver damage, dermatitis, mental deterioration, Parkinsonian paralysis, and insanity.

Ouch. While we probably don’t need to worry about our own exposure when knitting with this yarn, we should consider whether workers are exposed to unsafe levels of this chemical.
We might also worry about environmental effects:

Acute (short-term) ecological effects: Acute toxic effects may include the death of animals, birds, or fish, and death or low growth rate in plants. Acute effects are seen two to four days after animals or plants are exposed to a toxic chemical substance. Carbon disulfide has moderate acute toxicity to aquatic life. No data are available on the short-term effects of carbon disulfide to plants, birds, or land animals.
Chronic (long-term) ecological effects: Chronic toxic effects may include shortened lifespan, reproductive problems, lower fertility, and changes in appearance or behaviour. Chronic effects can be seen long after first exposure(s) to a toxic chemical. Carbon disulfide has high chronic toxicity to aquatic life. No data are available on the long-term effects of carbon disulfide to plants, birds, or land animals.

Fortunately, producers are developing organic solvents that may cause less environmental damage (1).
Seriously, who knew our yarn habits could have such serious environmental effects?
1. Environment friendly process for rayon. By: Narayan, Kudlip, Chemical Business, 09703136, Sep97, Vol. 11, Issue 2

Fiber Facts: Mercerized Cotton

In 1851, British chemist John Mercer discovered that treating cotton yarn with sodium hydroxide brought about changes in the fiber. Mercerized cotton is stronger, shinier, and smoother than untreated cotton. You can see the difference in the microscopic images of regular cotton and mercerized cotton below.
Regular cotton (above), appears coarse and uneven.

Mercerized cotton (above) appears smoother.

Unfortunately for John Mercer, mercerized cotton didn't really take off until later in the 19th century, when Horace Lowe added an extra step to the process and drummed up interest in the British cotton industry. Mercerized cotton is now widely available to knitters.

I don't want to scare anyone, but the sodium hydroxide used to make mercerized cotton is highly toxic. This is not to say that mercerized cotton yarn *itself* is bad for you, but it might be worth checking where and how these yarns are manufactured, since prolonged exposure can negatively affect workers. The CDC lists a wide array of health effects from exposure to sodium hydroxide:

Sodium hydroxide is very corrosive and can cause severe burns in all tissues that come in contact with it. Inhalation of low levels of sodium hydroxide as dusts, mists or aerosols may cause irritation of the nose, throat, and respiratory airways. Inhalation of higher levels can produce swelling or spasms of the upper airway leading to obstruction and loss of measurable pulse; inflammation of the lungs and accumulation of fluid in the lungs may also occur.

Ingestion of solid or liquid sodium hydroxide can cause spontaneous vomiting, chest and abdominal pain, and difficulty swallowing. Corrosive injury to the mouth, throat, esophagus, and stomach is very rapid and may result in perforation, hemorrhage, and narrowing of the gastrointestinal tract. Case reports indicate that death results from shock, infection of the corroded tissues, lung damage, or loss of measurable pulse.

Skin contact with sodium hydroxide can cause severe burns with deep ulcerations. Pain and irritation are evident within 3 minutes, but contact with dilute solutions may not cause symptoms for several hours. Contact with the eye may produce pain and irritation, and in severe cases, clouding of the eye and blindness.

Long-term exposure to sodium hydroxide in the air may lead to ulceration of the nasal passages and chronic skin irritation.

The U.S. Occupational Safety and Health Administration (OSHA) limits exposure in the workplace 2 milligrams of sodium hydroxide per cubic meter of air (2 mg/m³) per 8 hour day/40 hour work week. Nonetheless, in a study published in the American Journal of Industrial Medicine, textile workers in the cotton and wool industry in Croatia had higher rates of respiratory problems. In addition to sodium hydroxide, these workers were exposed to the following:

• direct dyes (sulfonated azo compounds)
• reductive dyes (indigo and indigo disodium salts, or anthraquinone derivate)
• disperse dyes (azo and anthraquinone structure of low molecular weight)
• naphtol dyes (azo with azochromophorm components)
• reactive dyes (azo and anthraquinone derivate-Cibakon E, Cibakon F)
• cation dyes (diphenylmethane derivate, triphenylmethane derivate, or triazine colors)
• sulfur dyes (sulfur compounds)
• acetic dyes (sodium salt of organic acids)
• acetic acid (CH3COOH)
• formic acid (HCOOH)
• sodium hydroxide (NaOH)
• sodium hydrosulfide (NaHS)
• potasium bicarbonate (KHCO3)
• chromium salt or ormaldehyde (HCHO).

Yikes! We might question the environmental effect of all these chemicals... In fact, after researching this I'm starting to wonder about non-organic yarns in general, as much as I love the wide array of intense colors and interesting fibers we can buy. Good thing there are plenty of organic yarns out there, not to mention ways of recycling yarn from sweaters and such!

Fiber Facts: The Forgotten Fiber Lanital (aka Aralac)

It is often said that necessity is the mother of invention. During World War II, wool was in short supply, in part because it was required to make military uniforms. Scientists in Italy and the United States searched for substitutes, including soy and milk, while in Japan and Germany scientists tried fish protein. For a while wool made from milk became an alternative to wool, cotton, and silk. The resultant fiber, called lanital in italy and aralac in the United States, was made in the following manner, according to a 1937 article in Time magazine:

Having practically the same chemical composition as wool, it is made by mixing acid with skim milk. This extracts the casein, which looks like pot cheese. Evaporated to crystals, it is pulverized and dissolved into a molasses consistency, then forced through spinnerets like macaroni, passed through a hardening chemical bath, cut into fibres of any desired length. From 100 pounds of skim milk come 3.7 pounds of casein which converts to the same weight of lanital.* Readily dyed, it can be distinguished from wool only by experts, is mothproof.

Aralac was said to be soft and serviceable, but customers complained that garments made from milk fiber smelled like sour milk when wet! Apparently, as the above image suggests, sweaters made from aralac also had the unfortunate effect of making your boobs look droopy. After the war, aralac production ceased as wool and cotton shortages abated. This probably explains why both sweaters and pointy, cone-shaped bras came into fashion in the 1950s.



*Images are from "Fabrics of the Future" by Robert D. Potter, The Science News-letter, February 7, 1940.

Fiber Facts: The physics of knots... or, why your yarn gets tangled

My mother is a great seamstress and a very crafty lady, and I learned to sew things as a child as part of our crafting. (The first thing I remember making, probably at the age of 5 or so, was a stuffed Grover head made out of old bits of leather my mom had scavenged from someplace--just a round head with no body.) My mom had a saying in German: "Langes Fädchen, faules Mädchen." Loosely translated, this means "Long thread, lazy girl." I swear she said this every single time I attempted to sew something. This refers, of course, to my tendency to use a superlong piece of thread so I could avoid tying off, threading the needle, etc. as much as possible. The problem with a long thread, though, is that it gets tangled and knotted up easily and ends up being just as much a pain in the ass as having to thread another needle. We all know my mom was right--but now scientists have explained why.

Researchers are interested in knots primarily because they hope to understand similar processes at a molecular level--apparently your DNA can get tangled up just like your yarn. But their ideas can tell us something about why we sometimes spend so much time detangling yarn that seems to form knots all by itself.

In a recent issue of the Proceedings of the National Academy of Sciences, Dorian Rymer and Douglas Smith explain that two main factors determine the degree of "knottiness" in a string--agitation and string length. Rymer and Smith tested this theory by dropping a string in a box, rotating and tumbling the box, and then examining the string and the types of knots that were formed. Then, they classified several different types of spontaneous knots (shown below):

(Apparently scientists are interested in knots in part because they look pretty--check out the images on The KnotPlot Site, for instance. )

The authors conclude the longer the string, and the more it is agitated, the more knots you will get. After a certain length, though, the knottiness factor levels off. The scientists also determined that it is the action of the free end of string that does the knotting, mostly by a kind of braiding motion that happens when the string is coiled (as in a skein of yarn, for instance). Unfortunately, they don't offer many tips for un-knotting string. Apparently modern science hasn't gotten that far yet. So the moral of the story is to keep your yarn short--just like my mom said.

Fiber Facts: The Science of Felting

I stumbled on this info from a 1883 book on microscopy, called Evenings at the Microscope by Philip Henry Gosse. Gosse examines hairs from several animals under the microscope, and explains why different kinds of wool felt differently. Mammal hairs felt because they are covered with "sheathing scales" (shown in his sketch, below). These scales mean that, when subjected to heat, motion, pressure, and moisture, the hairs become interlaced and entangled. Gosse gives the example of "worsted stockings," which "everyone knows ... shrink in their dimensions, but become much thicker and firmer after they have been worn and washed a little."

After examining different types of wool under a microscope, Gosse concluded that Saxon wool was of the highest quality for felting, because it possessed the greatest number of "serratures/inch," or the highest number of imbrications or connections between the fibers. He gave the following counts:
Saxon wool - 2, 720 serratures/inch
Merino wool - 2, 400 serratures/inch
South-Down wool - 2, 080 serratures/inch
Leicester - 1,850 serratures/inch

To the right is a more recent microscopic image of sheep's wool, from Florida State University--if you look closely, you can see the scales Gosse was describing.