What does “mercerized” cotton mean?

5 12 2012

fullsizeMercerization is a process applied to cellulosic  fibers  – typically cotton (or cotton-covered thread with a polyester core)  but hemp and linen can be mercerized also – to increase luster.  It is done after weaving (in the case of fabrics) or spinning (for yarns or threads).  But early on it was found that the process also had secondary benefits:  the mercerized fibers were able to absorb more water, and therefore absorb more dye, making the color of the dyed cloth brighter and deeper.  The difference is dramatic:  mercerization increases the absorption of dyestuffs by as much as 25%.[1]  unmercerized-101mercerized-101Not only is the color brighter, it also gives the cloth a better resistance to multiple washings,  keeping the colors bright and unchanged over time.   In addition to increasing luster and affinity to dyestuffs, the  treatment increases strength, smoothness, resistance to mildew, and also reduces lint.  So higher quality yarns and fabrics,  for example, are always mercerized.

The process goes back to the 1880’s.   John Mercer was granted a British Patent for his discovery that cotton and other fibers changed character when subjected to caustic soda (NaOh, also known as sodium hydroxide or lye), sulfuric acid, and/or other chemicals.   One of the changes was that caustic soda caused the fiber to swell, become round and straighten out.  But so what – these changes didn’t impart any luster to the fibers, so his patent was largely ignored.  Then in 1890 Horace Lowe found that by applying Mercer’s caustic soda process to cotton yarn or fabric under tension, the fabric gained a  high luster  as a result of the light reflection off the smooth, round surface created by the NaOH. It became an overnight success and revolutionized the cotton industry. The rest is history.[2]

Later testing proved that cotton fiber in its roving state (no twist in the yarns) would absorb more NaOH than fiber in a twisted state and as a result would absorb more water or dye.  Since fine, long stapled fiber gives the best absorption with the lowest twist, ( some twist is required for treating under tension to gain luster) it is usually the long fiber types of cotton (Sea Island, Egyptian, Pima) that are selected for yarn to be mercerized.   So mercerized cotton fabric starts with a better quality cotton fiber.

How is it done?

To get the desired luster and tensile strength,  cotton is held under specified tension for about ten minutes with an application of between 21%-23% caustic soda (NaOH) and wetting agents (used to facilitate the transfer of the NaOH into the fibers), at room temperature.  Then the fabric is neutralized in an acid bath.

Luster is a result of light reflection off a surface. The more glass like the surface, the better the luster. Yarn in its spun, treated state still has a very fine covering of tiny fiber ends (fuzz). This fuzz is removed by passing the yarn (or fabric) through a controlled heated atmosphere termed singeing (gas fired in the past, electric more currently) resulting in a cleaner surface.  (Luster is a result of light reflection off a surface. The more glass like the surface, the better the luster.)
You knew I’d have to look at the toxicity profile of sodium hydroxide, which is considered one of the building blocks of chemistry.  It’s a very powerful alkali.   It’s used in industry in a broad range of categories: chemical manufacturing; pulp and paper manufacturing; cleaning products such as drains, pipe lines and oven cleaners ; petroleum and natural gas; cellulose film;  and water treatment as well as textiles. The US Food and Drug Administration (FDA) considers sodium hydroxide to be generally safe, and recognizes it as not being found to pose unacceptable dietary risks, though it is generally only used on food contact surfaces rather than in foodstuffs.

The chemical is toxic to wildlife, and the EPA requires that effluent containing NaOH not be discharged into groundwater.  Because sodium hydroxide falls in the group of chemicals (salts) which are by far the most often used in textile processing, the sheer volume of NaOH used by the textile industry is important to recognize.  Usual salt concentrations in cotton mill wastewater can be 2,000 – 3,000 ppm[3], far in excess of Federal guidelines for in-stream salt concentrations of 230 ppm.  So treatment of effluent is very important, as prevention is the only reasonable alternative to solve the environmental problems associated with this hard-to-treat, high volume waste.  I have read that electrochemical cell treatment might be a substitute for using NaOH to mercerize.  This process occurs in a low voltage electrochemical cell that mercerizes, sours, and optionally bleaches without effluents and without the purchase of bulk caustic, neutralizing acids, or bleaches.

How to buy a quality sofa – part 4: synthetic fibers

3 10 2012

So from last week’s post, you  know that you want a durable, colorfast fabric that will be lovely to look at and wonderful to live with.  What’s the best choice?  I’m so glad you asked.

You have basically two choices in fibers:  natural (cotton, linen, wool, hemp, silk)  or synthetic (polyester, acrylic, nylon, etc.).  Many fabrics today are made from blends of natural and synthetic fibers – it has been said that most sheet sets sold in the U.S. are cotton/poly blends.

Natural fibres breathe, wicking moisture from the skin, providing even warmth and body temperature;  they are renewable, and decay at end of life.  On the other hand, synthetics do not breathe,  trapping body heat and perspiration; they are based on crude oil, definitely a non-renewable resource and they do not decompose at end of life, but rather remain in our landfills, leaching their toxic monomers into our groundwater.  They are, however, cheap and durable.

I like to think that even without the health issues involved I’d choose to live with natural fibers, since they work so well with humans!  The fibers themselves present no health issues and they’re comfortable.  But they simply don’t last as long as synthetics. But I have begun to see the durability of synthetics as their Dorian Grey aspect, in other words they last so long that they’ve become a huge problem.  By not decomposing, they just break into smaller and smaller particles which leach their toxic monomers into our groundwater.

The impact on health (ours the the planet’s) is an issue that’s often overlooked when discussing the merits of natural vs. synthetic.   And it’s a complex issue, so this week we’ll explore synthetic fibers, and next week we’ll look at natural fibers.

The most popular synthetic fiber in use today is polyester.

At this point, I think it would be good to have a basic primer on polyester production, and I’ve unabashedly lifted a great discussion from Marc Pehkonen and Lori Taylor, writing in their website diaperpin.com:

Basic polymer chemistry isn’t too complicated, but for most people the manufacture of the plastics that surround us is a mystery, which no doubt suits the chemical producers very well. A working knowledge of the principles involved here will make us more informed users.

Polyester is only one compound in a class of petroleum-derived substances known as polymers. Thus, polyester (in common with most polymers) begins its life in our time as crude oil. Crude oil is a cocktail of components that can be separated by industrial distillation. Gasoline is one of these components, and the precursors of polymers such as polyethylene are also present.

Polymers are made by chemically reacting a lot of little molecules together to make one long molecule, like a string of beads. The little molecules are called monomers and the long molecules are called polymers.

Like this:

O + O + O + . . . makes OOOOOOOOOOOOOOOO

Depending on which polymer is required, different monomers are chosen. Ethylene, the monomer for polyethylene, is obtained directly from the distillation of crude oil; other monomers have to be synthesized from more complex petroleum derivatives, and the path to these monomers can be several steps long. The path for polyester, which is made by reacting ethylene glycol and terephthalic acid, is shown below. Key properties of the intermediate materials are also shown.

The polymers themselves are theoretically quite unreactive and therefore not particularly harmful, but this is most certainly not true of the monomers. Chemical companies usually make a big deal of how stable and unreactive the polymers are, but that’s not what we should be interested in. We need to ask, what about the monomers? How unreactive are they?

We need to ask these questions because a small proportion of the monomer will never be converted into polymer. It just gets trapped in between the polymer chains, like peas in spaghetti. Over time this unreacted monomer can escape, either by off-gassing into the atmosphere if the initial monomers were volatile, or by dissolving into water if the monomers were soluble. Because these monomers are so toxic, it takes very small quantities to be harmful to humans, so it is important to know about the monomers before you put the polymers next to your skin or in your home. Since your skin is usually moist, any water-borne monomers will find an easy route into your body.

Polyester is the terminal product in a chain of very reactive and toxic precursors. Most are carcinogens; all are poisonous. And even if none of these chemicals remain entrapped in the final polyester structure (which they most likely do), the manufacturing process requires workers and our environment to be exposed to some or all of the chemicals shown in the flowchart above. There is no doubt that the manufacture of polyester is an environmental and public health burden that we would be better off without.

What does all of that mean in terms of our health?  Just by looking at one type of cancer, we can see how our lives are being changed by plastic use:

  • The connection between plastic and breast cancer was first discovered in 1987 at Tufts Medical School in Boston by research scientists Dr. Ana Soto and Dr. Carlos Sonnenschein. In the midst of their experiments on cancer cell growth, endocrine-disrupting chemicals leached from plastic test tubes into the researcher’s laboratory experiment, causing a rampant proliferation of breast cancer cells. Their findings were published in Environmental Health Perspectives (1991)[1].
  • Spanish researchers, Fatima and Nicolas Olea, tested metal food cans that were lined with plastic. The cans were also found to be leaching hormone disrupting chemicals in 50% of the cans tested. The levels of contamination were twenty-seven times more than the amount a Stanford team reported was enough to make breast cancer cells proliferate. Reportedly, 85% of the food cans in the United States are lined with plastic. The Oleas reported their findings in Environmental Health Perspectives (1995).[2]
  • Commentary published in Environmental Health Perspectives in April 2010 suggested that PET might yield endocrine disruptors under conditions of common use and recommended research on this topic. [3]

These studies support claims that plastics are simply not good for us – prior to 1940, breast cancer was relatively rare; today it affects 1 in 11 women.  We’re not saying that plastics alone are responsible for this increase, but to think that they don’t contribute to it is, we think, willful denial.  After all, gravity existed before Newton’s father planted the apple tree and the world was just as round before Columbus was born.

Polyester fabric is soft, smooth, supple – yet still a plastic.  It contributes to our body burden in ways that we are just beginning to understand.  And because polyester is highly flammable, it is often treated with a flame retardant, increasing the toxic load.  So if you think that you’ve lived this long being exposed to these chemicals and haven’t had a problem, remember that the human body can only withstand so much toxic load – and that the endocrine disrupting chemicals which don’t seem to bother you may be affecting generations to come.

And then there is acrylic.  The key ingredient of acrylic fiber is acrylonitrile, (also called vinyl cyanide). It is a carcinogen (brain, lung and bowel cancers) and a mutagen, targeting the central nervous system.  According to the Centers for Disease Control and Prevention, acrylonitrile enters our bodies through skin absorption, as well as inhalation and ingestion.  So could the acrylic fibers in our acrylic fabrics be a contributing factor to these results?

Acrylic fibers are just not terrific to live with anyway.  Acrylic manufacturing involves highly toxic substances which require careful storage, handling, and disposal. The polymerization process can result in an explosion if not monitored properly. It also produces toxic fumes. Recent legislation requires that the polymerization process be carried out in a closed environment and that the fumes be cleaned, captured, or otherwise neutralized before discharge to the atmosphere.(4)

Acrylic is not easily recycled nor is it readily biodegradable. Some acrylic plastics are highly flammable and must be protected from sources of combustion.

Just in case you missed the recent report which was published in Occupational and Environmental Medicine [5], a Canadian study found that women who work with some common synthetic materials could treble their risk of developing breast cancer after menopause. The data included women working in textile factories which produce acrylic fabrics – those women have seven times the risk of developing breast cancer than the normal population, while those working with nylon fibers had double the risk.

What about nylon?  Well, in a nutshell, the production of nylon includes the precursors benzene (a known human carcinogen) and hydrogen cyanide gas (extremely poisonous); the manufacturing process releases VOCs, nitrogen oxides and ammonia.  And finally there is the addition of those organophosphate flame retardants and dyes.

[1] http://www.bu-eh.org/uploads/Main/Soto%20EDs%20as%20Carcinogens.pdf

[2] http://ehp03.niehs.nih.gov/article/fetchArticle.action?articleURI=info:doi/10.1289/ehp.95103608

[3] Sax, Leonard, “Polyethylene Terephthalate may Yield Endocrine Disruptors”,
Environmental Health Perspectives, April 2010, 118 (4): 445-448

(4) ) http://www.madehow.com/Volume-2/Acrylic-Plastic.html

(5) Occupational and Environmental Medicine 2010, 67:263-269 doi: 10.1136/oem.2009.049817 (abstract: http://oem.bmj.com/content/67/4/263.abstract) SEE ALSO: http://www.breastcancer.org/risk/new_research/20100401b.jsp AND http://www.medpagetoday.com/Oncology/BreastCancer/19321

Listmania: LBC Red List and others

19 06 2012

I love lists – you know, all those “best of” lists – movies, books, toxic chemicals.

Having a list makes it easy for us to tick off those bad chemicals that nobody wants to live with.  And in the building industry there have been a proliferation of lists which identify chemicals of concern:  the Perkins & Will Precautionary List, the LEED Pilot 11 and the Living Building Challenge Red List, among others.  And make no mistake, we think it’s critical that we begin to develop these lists, because we all need a baseline.   As long as we need to eat and breathe, toxics should be an important consideration.  We just have a problem with  how these lists are used.

So let me explain.

First, lists for the most part are developed on the basis of science that usually occurred five or 10 years ago, so they can  (though not always) be lagging indicators of safety to humans and the environment.  (But that’s a minor point, just wanted us to remember to maintain those lists.)

When using lists, it’s important to remember the concept of reactive chemistry:  many of the chemicals, though possibly deemed to be benign themselves, will react with other chemicals to create a third substance which is toxic.   This reaction can occur during the production of inputs, during the manufacture of the final product, or at the end of life (burning at the landfill, decomposing or biodegrading).   So isn’t it important to know the manufacturing supply chain and the composition of all the products – even those which do not contain any chemicals of concern on the list you’re using – to make sure there are no, say … dioxins created during the burning of the product at the landfill, for example?

It’s also important to remember that  chemicals are synergistic  – toxins can make each other more toxic.  A small dose of mercury that kills 1 in 100 rats and a dose of aluminum that will kill 1 in 100 rats, when combined, have a striking effect: all the rats die.  So if the product you’re evaluating is to be used in a way that introduces a chemical which might react with those in your product, shouldn’t that be taken into consideration?

So, O.K., the two problems above would be extremely difficult to define  – I mean, wouldn’t you need a degree in chemistry, not to mention the time and money, to determine if these could occur .  The average consumer wouldn’t have a clue.  Just wanted you to know that these problems do exist and contribute to our precautionary admonition regarding lists.

Each list has a slightly different interpretation – and lists different chemicals.  The Healthy Building Network published this Venn diagram of several of the most prevalent lists used in building materials:

The real reason we don’t like the way lists are used is that people see the list, are convinced by a manufacturer that their product doesn’t contain any of the chemicals listed, so without any further ado the product is used.

What does that mean in the textile industry, for example?

By attempting to address all product types, most lists do not mention many of the toxic chemicals which ARE used in textile processing. In the Living Building Challenge Red List, no mention is made of polyester, the most popular fiber for interiors, which itself is made from two toxic ingredients (ethylene glycol and terephthalic acid – both carcinogens, neither of which are on the list).  That means  a fabric made of polyester – even recycled polyester – that has been processed using some pretty nasty chemicals – could be specified.   Chemicals which are commonly used in textile processing  and which are NOT included on the Living Building Challenge Red List, for example,  but which have been found to be harmful , include:

Chlorine   (sodium hypochlorite NaOCL); registered in the Toxic Substances Control Act   as hypochlorous acid ; sodium chlorite
Sodium cyanide;   potassium cyanide
sodium sulfate   (Na2SO4)
Sodium sulfide
 APEOs ( Alkylphenolethoxylates)
Chromium III   and VI (hexavalent chromium)
pentachlorophenol   (PCP)
Dichloromethane   (DCM, methylene chloride)
Tetrachloroethylene   (also known as perchloroethylene, perc and PCE)
Methyl ethyl   ketone
Toluene:   toluene diisocyanate and other aromatic amines
Methanol (wood   alcohol)
Chloroform;   methyl chloroform
Phosphates   (concentrated phosphoric acid)
Dioxin –   by-product of chlorine bleaching; also formed during synthesis of certain   textile chemicals
Benzenes and   benzidines; nitrobenzene; C3 alkyl benzenes; C4 alkyl benzenes
Sulfuric Acid
Optical   brighteners: includes several hundred substances, including triazinyl   flavonates; distyrylbiphenyl sulfonate
ethylenediaminetetra   acetic acid [EDTA]
diethylenetriaminepenta   acetic acid [DTPA]
Perfluorooctane   sulfonates (PFOS)

In the case of arsenic (used in textile printing and in pesticides) and pentachlorophenol (used as a biocide in textile processing) – the Living Building Challenge Red List expressly forbids use in wood treatments only, so using it in a textile would qualify as O.K.

Perhaps we should manufacture with a “green list” in mind: substituting chemicals and materials that are inherently safer, ideally with a long history of use (so as to not introduce completely new hazards)?

But using any list of chemicals of concern ignores what we consider to be the most important aspect needing amelioration in textile processing – that of water treatment.  Because the chemicals used by the textile industry include many that are persistent and/or bioaccumulative which can interfere with hormone systems in people and animals and may be carcinogenic and reprotoxic, and because the industry often ignores water treatment even when it is required (chasing the lowest cost) the cost of dumping untreated effluent into our water is incalculable.

The textile industry uses a LOT of water – according to the World Bank, 20% of industrial freshwater pollution is from the textile industry; that’s another way of saying that it’s the #1 industrial polluter of water on the planet.  In India alone textile effluent averages around 425,000,000 gallons per day, largely untreated[1].   The chemically infused effluent – saturated with dyes, de-foamers, detergents, bleaches, optical brighteners, equalizers and many other chemicals –  is often released into the local river, where it enters the groundwater, drinking water, the habitat of flora and fauna, and our food chain.  The production of polychlorinated biphenyls (PCBs) were banned in USA more than 30 years ago (maybe that’s why they’re not listed on any of these lists?), but are still showing up in the environment as unintended byproducts of  the chlorination of wastes in sewage disposal plants that have a large input of biphenyls (used as a dye carrier) from textile effluent.[2]

Please click HERE to see the PDF by Greenpeace on their new campaign on textile effluent entitled  “Dirty Laundry”, which points the finger at compliant corporations which basically support what they call the “broken system”.  It asks corporations to become champions for a post toxic world, by putting in place policies to eliminate the use and release of all hazardous chemicals across a textile company’s entire supply chain based on a precautionary approach to chemicals management, to include the whole product lifecycle and releases from all pathways.

Another problem in the textile industry which is often overlooked is that of end of life disposal.  Textile waste in the UK, as reported by The Ecologist, has risen from 7% of all waste sent to landfills to 30% in 2010.[3]  The US EPA estimates that textile waste account for 5% of all landfill waste in the U.S.[4]  And that waste slowly seeps chemicals into our groundwater, producing environmental burdens for future generations.  Textile sludge is often composted, but if untreated,  that compost is toxic for plants.[5]

What about burning:    In the United States, over 40 million pounds of still bottom sludge from the production of ethylene glycol (one of the components of PET fibers) is generated each year. When incinerated, the sludge produces 800,000 lbs of fly ash containing antimony, arsenic and other metals.[6]

These considerations are often neglected in looking at environmental pollution by textile mills[7] – but is never a consideration on a list of chemicals of concern.

So yes, let’s recognize that there are chemicals which need to be identified as being bad, but let’s also look at each product and make some kind of attempt to address any other areas of concern which the manufacture of that product might raise.  Using a list doesn’t get us off the hook.

[1] CSE study on pollution of Bandi river by textile industries in Pali town, Centre for Science and Environment,New Delhi, May 2006 and “Socio-Economic, Environmental and Clean Technology Aspects of Textile Industries in Tiruppur,South India”, Prakash Nelliyat, Madras School of Economics.  See also:

Jacks Gunnar et al (1995), “The Environmental Cost of T-Shirts”, Sharing Common Water Resources, First Policy Advisory Committee Meeting, SIDA, Madras Institute of Development Studies, Chennai.

Also:  CSE: Down to Earth Supplement on Water use inIndia, “To use or to misuse”;  http://www.cseindia.org/dte-supplement/industry20040215/misuse.htm

[3] Ecologist, “’Primark effect’ sill clogging up UK landfills”, January 19, 2010,  http://www.newsinferno.com/legal-news/possible-link-between-formaldehyde-lou-gehrigs-disease-found/2926

[5] Scientia Agricola, vol. 62, no 3 May/June 2005

[6] Sustainable Textile Development at Victor,  http://www.victor-innovatex.com/doc/sustainability.pdf

[7] Assuming a beginning value of 375ppm of antimony in an undyed polyester fiber, as much as 175ppm of antimony can be leached from the fiber during the dyeing process. This seemingly insignificant amount translates into a burden on water treatment facilities and is still a hazardous waste when precipitated out during treatment. The U.S. EPA lists the allowable limit for antimony in drinking water to be 6 parts per billion (ppb). Countries that can afford technologies that precipitate the metals out of the water are left with a hazardous sludge that must then be disposed of in a properly managed landfill or incinerator operations. Countries who cannot, or who are unwilling to employ these end-of-pipe treatments, release antimony along with a host of other dangerous substances to open waters. Victor Defining Sustainability, http://www.victor-innovatex.com/doc/sustainability.pdf

What about chrome-free, or “eco” leather?

29 05 2012

With the increased interest in avoidance of certain chemicals and industrial products that are particularly harmful to our environment, it’s not surprising that manufacturers are becoming ingenious in pointing out attributes that play to this script.  So we now see claims for “chrome free” leather, or for “eco friendly” leather.

In last week’s post, I pointed out two kinds of leather tanning – chromium and vegetable. Although most leather is tanned using chromium (from 80 – 95% of all leather produced[1]) there is a third type of leather tanning, called aldehyde tanning, which like vegetable tanning does not use chromium.  Let’s revisit leather tanning for a minute:

  1. Sometimes leather manufacturers will tell you that they don’t use the toxic form of chromium in tanning – the toxic form is called chromium IV or hexavalent chromium.  And that is correct:  chromium tanned leathers use chromium III salts (also called trivalent chromium) in the form of chromium sulfate.  This form of chromium is found naturally in the environment and is a necessary nutrient for the human body.   However, the leather manufacturers fail to explain that  chromium III oxidizes into chromium IV in the presence of oxygen combined with other factors, such as extremes in pH.  This happens during the tanning process.  Chromium-tanned leather can contain between 4 and 5% of chromium [2] – often hexavalent chromium, which produces allergic reactions and easily moves across membranes such as skin.  End of life issues, recovery and reuse are a great concern – chromium (whether III or IV) is persistent (it cannot be destroyed) and will always be in the environment.   Incineration, composting and gasification will not eliminate chromium.
  2. Vegetable tanning is simply the replacement of the chromium for bark or plant tannins – all other steps remain the same.  And since there are about 250 chemicals used in tanning, the replacement of chromium for plant tannins, without addressing the other chemicals used, is a drop in the bucket.   Last week I mentioned some of the other 249 chemicals routinely used in tanning:  alcohol, coal tar , sodium sulfate, sulfuric acid, chlorinated phenols (e.g. 3,5-dichlorophenol), azo dyes, cadmium, cobalt, copper, antimony, cyanide, barium, lead, selenium, mercury, zinc, polychlorinated biphenyels (PCBs), nickel, formaldehyde and pesticide residues.[3]   Here are the steps to creating leather :
  3. Aldehyde tanning is the main type of leather referred to as “chrome-free”, and is often used in automobiles and baby’s shoes.  Aldehyde tanning is often referred to as “wet white” due to the pale cream color it imparts to the skins.  But aldehydes are a group of chemicals that contain one chemical which many people are familiar with: formaldehyde.  And we all know about formaldehyde: it is highly toxic to all animals; ingestion of as little as little as 30 mL (1 oz.) of a solution containing 37% formaldehyde has been reported to cause death in an adult human[4]  and the Department of Health and Human Services has said it may reasonably be anticipated to be a carcinogen.  Aldehyde tanning essentially uses formaldehyde, which reacts with proteins in the leather to prevent putrefication.  BLC Leather Technology Centre,  a leading independent leather testing center, states that leathers should contain no more than 200ppm of formaldehyde for articles in general use. If the item is in direct skin contact this should be 75ppm, and 20ppm for items used by babies (<36 months). Typically, with modern tanning techniques, leathers contain 400ppm or less.[5]   Yet that far exceeds levels set elsewhere – in New Zealand, for example, acceptable levels of formaldehyde in products is set at 100 ppm[6]  – the European Union Ecolabel restricts formaldehyde to 20 ppm for infant articles, 30 ppm for children and adults, while GOTS prohibits any detectable level.

BLC Leather Technology Centre Ltd.  commissioned a study by Ecobilan S.A (Reference BLC Report 002)  to do a life cycle analysis to evaluate the various tanning chemicals, to see if there was an environmentally preferable choice between chrome, vegetable and aldehyde based processes.  The result?  They found no significant differences between the three  – all have environmental impacts, just different ones.  These LCA’s demonstrate that tanning is just one of the impacts – other steps may have equal impacts.   Chrome was sited as having the disadvantage of being environmentally persistent. “Another consideration, in terms of end-of-life leather or management of chrome tanned leather waste, is the possibility of the valency state changing from the benign Cr III to the carcinogenic Cr VI.”[7]

So much for “chrome free” leather.  What about claims for “eco leather”?

In the strict sense of the definition, the term “eco leather” is meaningless. However, retailers want to imply improved environmental performance. So how can you evaluate their claims for “eco leathers”?

There are two main considerations in making leather:

  • How is it manufactured?
  • What inputs are used to produce it?

Research has shown that a significant part of the environmental impact of leather is in the manufacturing process.  In this respect it is the environmental stewardship practice of tanners coupled with chemical selection that should determine how eco friendly a leather is.  The following areas of leather manufacture have the most significant potential impact:

  • Management of restricted substances
  • Energy consumption
  • Air emissions
  • Waste management (hazardous and non hazardous)
  • Environmental management systems
  • Water consumption
  • Control of manufacturing processes
  • Effluent treatment
  • Chrome management
  • Traceability of material

In terms of the selection of inputs, we should consider the use of certain materials that could give an improved eco profile to leather. These include:

  • Biodegradable wetting agents for soaking
  • Reduced sulphide processing
  • Non synthetic or polymeric re-tannage systems
  • optimized dyestuffs
  • Vegetable oil based fatliquors
  • Optimised finishing systems to reduce waste such HVLP or roller coating
  • Biodegradable in 12 months or less

In summary, although there is no current definition, these are the key elements which should determine an “eco leather”:

  1. Control of leather manufacturing processes
  2. Clean technology chemical selection in the process
  3.  Effective management of restricted substances within the leather
  4. A measure of the end of life impact

As I mentioned in last week’s post, the production of leather can be a hellish life for the animal.  I have found only one company, Organic Leather, which looks beyond the production of the leather itself to the important questions of animal husbandry and land management practices which provide the skins, and incorporate these into a tanning process which “prevents further toxicity entering our environment and our bodies.”

The Leather Working Group (LWG)   is a multi-stakeholder group[8], whose purpose is  “to develop and maintain a protocol that assesses the compliance and environmental performance of tanners and promotes sustainable and appropriate environmental business practices within the footwear leather industry.”   The LWG, in conjunction with BLC Leather Technology Center Ltd., operates an eco rating system for leather. (This sort of mark is known as a first or second party certification, and lacks – I believe – the credibility of a true third party certification.)   Retailers, brands or tanners who are able to meet the requirements of this standard are eligible to use the EcoSure mark. To be eligible to use this mark tanneries must have achieved at least a Bronze award in the LWG Tannery Environment Auditing Protocol,  and the finished leather on which the mark is to be used must meet the requirements of the audit and testing regime. (to see the audit form, click here  ).

One issue which is a hot topic in leather production is that of deforestation and the sourcing of skins from Brazil – cattle ranching in Brazil accounted for 14% of global deforestation and ranches occupy approximately 80% of all deforested land in the Amazon.[9]  Greenpeace and the National Wildlife Federation (NWF) aims to stop all deforestation in the Amazon by encouraging the meat processors to insist that their suppliers register their farms and map and log their boundaries as a minimum requirement. They also encourage companies to cancel orders with suppliers that are not prepared to stop deforestation and adhere to these minimum requirements.  Many of the LWG member brands have  made commitments to a moratorium on hides sourced from farms involved in deforestation and LWG itself has a project to identify and engage with the key stakeholders in Brazil, investigate traceability solutions, conduct trials and implement third party auditing solutions.

[1] Richards, Matt, et al, “Leather for Life”, Future Fashion White Papers, Earth Pledge Foundation

[2] Gustavson, K.H. “The Chemistry of Tanning Processes” Academic Press Inc., New York, 1956.

[3] Barton, Cat, “Workers pay high price at Bangladesh tanneries”, AFP, Feb. 2011

[4] Agency for Toxic Substances & Disease Registry, “Medical management guidelines for formaldehyde”, http://www.atsdr.cdc.gov/mmg/mmg.asp?id=216&tid=39

[5] BLC Leather Technology Center Ltd, “Technology Restricted substances – Formaldehyde”, Leather International,  November 2008,  http://www.leathermag.com/news/fullstory.php/aid/13528/Technology_Restricted_substances-Formaldehyde.html

[6] “Evaluation of alleged unacceptable formaldehyde levels in Clothing”, Wellington, New Zealand: New Zealand Ministry of Consumer Affairs, October 17, 2007.

[8] Currently the consumer brands involved with the LWG are: Adidas-group, Clarks International, Ikea of Sweden, New Balance Athletic Shoe, Nike Inc, Pentland Group including (Berghaus, Boxfresh, Brasher, Ellesse, Franco Sarto, Gio-Goi, Hunter, KangaROOS, Mitre, Kickers (UK), Lacoste Chaussures, ONETrueSaxon, Radcliffe, Red or Dead, Speedo, Ted Baker Footwear), The North Face, The Timberland Company, Wolverine World Wide Inc including (CAT, Merrel, Hush Puppies, Patagonia, Wolverine, Track n Trail, Sebago, Chaco, Hytest, Bates, Cushe, Soft Style). New brands recently joined are Airwair International Ltd, K-Swiss International, Marks & Spencers and Nine West Group.

[9] “Broken Promises: how the cattle industry in the Amazon is still connected to deforestation…” Greenpeace, October 2011; http://www.leatherworkinggroup.com/images/documents/Broken%20promises%20-%20Oct11FINAL.pdf

Printing – part 3

19 01 2012

Yes, we’re still talking about the printing process!  As I warned you, it’s complicated.

For the past two weeks we’ve concentrated on the first two steps of the basic 5 steps in printing a fabric, which  are:

1. Preparation of the print paste.

2. Printing the fabric.

3. Drying the printed fabric.

4. Fixation of the printed dye or pigment.

5. Afterwashing.

So let’s look at the rest of the steps – drying, fixation and afterwashing.

Actually, the printing process begins even before passing  the fabric thru the printing presses, because the fabric must be conditioned.  The cloth must always to be brushed, to free it from loose nap, flocks and dust that it picks up while stored. Frequently, too, it has to be sheared by being passed over rapidly revolving knives arranged spirally round an axle, which rapidly and effectually cuts off all filaments and knots, leaving the cloth perfectly smooth and clean and in a condition fit to receive impressions of the most delicate engraving. Some figured fabrics, especially those woven in checks, stripes and crossovers, require very careful stretching and straightening on a special machine, known as a stenter, before they can be printed with certain formal styles of pattern which are intended in one way or another to correspond with the cloth pattern. Finally, all descriptions of cloth are wound round hollow wooden or iron centers into rolls of convenient size for mounting on the printing machines.

Immediately after printing, the fabric must be dried  in order to retain a sharp printed mark and to facilitate handling between printing and subsequent processing operations.

Two types of dryers are used for printed fabric, steam coil or natural gas fired dryers, through which the fabric is conveyed on belts, racks, etc., and steam cans, with which the fabric makes direct contact. Most screen printed fabrics and practically all printed knit fabrics and terry towels are dried with the first type of dryer, not to stress the fabric. Roller printed fabrics and apparel fabrics requiring soft handling are dried on steam cans, which have lower installation and operating costs and which dry the fabric more quickly than other dryers.

After printing and drying, the fabric is often cooled by blowing air over it or by passing it over a cooling cylinder to improve its storage properties prior to steaming, which is the process which fixes the color into the fabric.  Steaming may be likened to a dyeing operation.  Before steaming, the bulk of the dyestuff is held in a dried film of thickening agent.  During the steaming operation, the printed areas absorb moisture and form a very concentrated dyebath, from which dyeing of the fiber takes place.  The thickening agent prevents the dyestuff from spreading outside the area originally printed, because the printed areas act as a concentrated dyebath that exists more in the form of a gel than a solution and restricts any tendency to bleed.  Excessive moisture can cause bleeding, and insufficient moisture can prevent proper dyestuff fixation.  Steaming is generally done with atmospheric steam, although certain tyepes of dyestuffs, such as disperse dyes, can be fixed by using superheated steam or even dry heat.  In a few instances, acetic or formic acid is added to the steam to provide the acid atmosphere necessary to fix certain classes of dyes.  Temperatures in the steamer must be carefully controlled to prevent damage from overheating due to the heat swelling of the fabric, condensation of certain chemicals, or the decomposition of reducing agents.

Flash aging is a special fixation technique used for vat dyes. The dyes are printed in the insoluble oxidized state by using a thickener which is very insoluble in alkali. The dried print is run through a bath containing alkali and reducing agent, and then directly into a steamer, where reduction and color transfer take place.

After steaming, the printed fabric must not be stored for too long prior to washing because reducing agent residues may continue to decompose, leading to heat build up in the stacked material and defective dyeing or even browning of the fibers. If a delay of several hours is anticipated before the wet aftertreatment the fabric should be cooled with air (called “skying”) to oxidize at least some of the excess reducing agent.

Finally, printed goods must be washed thoroughly to remove thickening agent, chemicals, and unfixed dyestuff.  Washing of the printed material begins with a thorough rinsing in cold water.  After this, reoxidation is carried out with hydrogen peroxide in the presence of a small amount of acetic acid at 122 – 140 degrees F. A soap treatment with sodium carbonate at the boiling point should be begun only after this process is complete. This washing must be carefully done to prevent staining of the uncolored portions of the fabric.  Drying of the washed goods is the final operation of printing. 

And there you have it – a beautifully printed fabric that you can proudly display. Bet you know the subject of the next post – the environmental consequences of all this. Stay tuned.

Certifications: Oeko Tex

28 07 2011

I have an apology to make:  I made a statement last week that turns out to be incorrect, based on experience from years ago.  I said

“it’s not unusual to find a GOTS certification logo on a product – because it’s hard to get, and those who have it certainly want to display the logo.  But the certification may apply only to the organic fibers – the logo itself is not specific as to what is being certified.”

Laurie Lemmlie-Leung, of Sapphire International, Ltd, which is a GOTS certified terry mill, pointed out that in their experience,  “If we do not have an approved “GOTS Product Specification Plan” and transaction certificates showing that all the inputs are also GOTS certified, then we cannot use the GOTS label on the product.”  And that is indeed the case:  a GOTS logo on any product means that all processing up to the final product is GOTS certified.  So if GOTS certified cotton yarn is being sold, it can display the logo.  However, if that yarn is used to weave a fabric in a non-certified facility, the final fabric cannot display the logo.

So when you see a GOTS logo on a product, you can rest assured that the entire supply chain has been certified.

Now, back to discussion of certifications:  Before giving a summary of the main points of each of the certifications which deal with fiber processing (i.e., weaving), it’s important to remember that most of these certification programs are in business – so it costs money to achieve the certification – sometimes it costs a LOT of money.  In addition there is the burden of documentation, which increases administrative costs for the manufacturer.

Cradle to Cradle and GreenGuard can cost quite a bit, so when you look on the web sites to find which products have these certifications,  you see mostly large, well established companies which can afford to absorb the certification costs.  On the GreenGuard website, for example, it lists 1943 individual products, but all 1943 products are manufactured by only 20 large, well-known companies.  Sometimes smaller manufacturers decide not to pay the costs of certification, even though they may be doing everything “by the book”, because they’re operating on a shoestring.  Unfortunately, the many unethical claims make third party certification a requirement.

In addition to certifications, there are many new “green guides” on the internet which purport to list green products.  Some are valiantly trying to make order out of chaos, while others are simply adding to the confusion.  Of these, a basic listing may (or may not) be free, but any additional bells and whistles costs money.  So green products may be specially featured or identified (sometimes as “best”) because the manufacturer has paid for the spotlight.  The same is true of television shows which purport to cover new green products.  We have been approached several times by television programs featuring a well-known personality who would wax eloquently about our fabrics – if only we were to pay the right price.

What does this all mean?  Do your own homework!  Most of these “experts” have no more knowledge than you do.  And again, certifications provide a reliable yardstick to determine quality standards.

The third party certifications which cover textile processing and/or final products which you’ll see most often include:

  • Oeko Tex
  • GreenGuard
  • Cradle 2 Cradle by MBDC
  • Global Organic Textile Standard
  • Global Recycle Standard
  • SMART Sustainable Textile Standard

These are the certifications you’re most likely to run into, and they are very different.  So different, in fact, that we’ll take a few weeks to explore what each one tells us.

This week, we’ll start with one of the oldest certifications:  Oeko Tex.

Oeko Tex is an independent, third party certifier that offers two certifications for textiles:

  1. Oeko-Tex 100 (for products)
  2. Oeko-Tex 1000 (for production sites/factories).

Products satisfying the criteria for Oeko-Tex 100 which are produced in an Oeko-Tex 1000 certified facility may use the Oeko-Tex 100Plus mark, which is simply a combination of the two.

Oeko Tex was founded in 1992, by the Austrian Textile Research Intitute (OTI) and the German Research Institute Hohenstein,  to provide an objective and reliable product label for consumers.  Its aim is to ensure that products posed no risk to health.

Oeko Tex Standard 100

The Oeko-Tex Standard 100 standard is concerned primarily with health and safety of textile products – it tests only the end product.  The processing is not addressed – for example, wastewater treatment is not included.   It is NOT an organic certification and products bearing this mark are not necessarily made from organically grown fibers. (Note:  When you see the logo, make sure that the test number is quoted (No. 11-20489 in the image above)  and the test institute is named (Shirley is the institute which tested the product).)

Textiles considered for this standard are classified into four categories, and each category has different test values for chemicals allowed in the product:

  • Product Class I: Products for Babies – all textile products and materials used to manufacture such textile products for children up to the age of 36 months (leather clothing is excepted)
  • Product Class II: Products with Direct Contact to Skin – worn articles of which a large surface touches the skin (i.e. underwear, shirts, pants)
  • Product Class III: Products without Direct Contact to Skin – articles of which only a small part of their surface touches the skin (i.e. linings, stuffings)

Textile products bearing the Oeko-Tex 100 certification mark:

  • Do not contain allergenic dye-stuffs and dye stuffs that form carcinogenic arylamines.
  • Have been tested for pesticides and chlorinated phenoles.
  • Have been tested for the release of heavy metals under artificial perspiration conditions.
  • Formaldehyde is banned; other aldehyde limits are significantly lower than the required legal limits.
  • Have a skin friendly pH.
  • Are free from chloro-organic carriers.
  • Are free from biologically active finishes.

The certification process includes thorough testing for a lengthy list of chemicals, including lead, antimony, arsenic, phthalates, pesticides, and chlorinated phenols. The official table of limits for tested chemicals may be found on the Oeko-Tex website.  Specifically banned are:

  • AZO dyes
  • Carcinogenic and allergy-inducing dyes
  • Pesticides
  • Chlorinated phenols
  • Chloro-organic benzenes and toluenes
  • Extractable heavy metals
  • Phthalates in baby articles
  • Organotin compounds(TBT and DBT)
  • Emissions of volatile components

Certification may be given to a finished product (such as a shirt), or to individual components (such as yarn, or fabric).

Oeko-Tex Standard 1000

The Oeko-Tex 1000 is a certification for environmentally-friendly textile production.
The goal of the Oeko-Tex 1000 Standard is to be “an evaluation of the environmental performance of textile production sites and products and to document independently that certain environmental measures are undertaken and a certain level achieved.”

The evaluation process includes considerations for:

  • environmental impact: energy consumption, whether materials used are renewable or non-renewable, and the overall impact of the space utilized
  • global impact: use of fossil fuels, use of ozone-depleting chemicals regional impact: VOC’s, water contamination, acidification of soil and water from fossil fuel use, emissions (often from chlorine bleaching)
  • local effects: emissions, workplace contamination, noise, use of dangerous chemical products

The mark is not applied directly to products, but may be used by the production site (for example, on its letterhead and official documents). The “local effects” consideration does NOT include an evaluation of labor practices and is not meant to be an indicator of whether a production site is following fair labor practices.

Oeko-Tex 100Plus

This label may be used on products that have met the Oeko-Tex 100 Standard and are also produced in a facility that meets the Oeko-Tex 1000 Standard.

So, these are the important points to keep in mind when you see the Oeko Tex logo:

  1. Oeko Tex 100 is product specific – they don’t look at processing (i.e., water treatment, workers rights, emissions, sludge), it only means that the finished product (fabric, yarn, clothing, etc.) has limit values for chemicals which are below the threshold limits on the Oeko Tex list, with many specifically prohibited.
  2. Oeko Tex 1000 is site specific, and documents that certain environmental standards are met, but these do not include workers rights issues.
  3. Oeko Tex 100+ means that the site meets environmental standards and the product itself is safe to use.

When is recycled polyester NOT recycled polyester?

23 03 2011

Fabric might be the only product I can think of which is known by its component parts, like cotton, silk, wool.  These words usually refer to the fabric rather than the fiber used to make the fabric.  We’ve all done it: talked about silk draperies, cotton sheets.  There seems to be a disassociation between the fibers used and the final product, and people don’t think about the process of turning cotton bolls or silkworm cocoons or flax plants into luxurious fabrics.

There is a very long, involved and complex process needed to turn raw fibers into finished fabrics.  Universities award degrees in textile engineering,  color chemistry or any of a number of textile related fields.  One can get a PhD in fiber and polymer science,  or study the design, synthesis and analysis of organic dyes and pigments.  Then there is the American Association of Textile Chemists and Colorists (AATCC) which has thousands of members in 60 different countries.  My point is that we need to start focusing on the process of turning raw textile fiber into a finished fabric – because therein lies all the difference!

And that brings me to recycled polyester, which has achieved pride of place as a green textile option in interiors.  We have already posted blogs about plastics (especially recycled plastics) last year (on 4.28.10, 5.05.10 and 5.12.10) so you know where we stand on the use of plastics in fabrics.  But the reality is that polyester bottles exist,  and recycling some of them  into fiber seems to be a better use for the bottles than landfilling them.

But today the supply chains for recycled polyester are not transparent, and if we are told that the resin chips we’re using to spin fibers are made from bottles – or from any kind of  polyester  –  we have no way to verify that.  Once the polymers are at the melt stage, it’s impossible to tell where they came from, because the molecules are the same.  So the yarn/fabric  could be virgin polyester or  it could be recycled.   Many so called “recycled” polyester yarns may not really be from recycled sources at all because – you guessed it! – the process of recycling is much more expensive than using virgin polyester.   And unfortunately not all companies are willing to pay the price to offer a real green product, but they sure do want to take advantage of the perception of green.   So when you see a label that says a fabric is made from 50% polyester and 50% recycled polyester – well, there is absolutely no way to tell if that’s true.

Some companies are trying to differentiate their brands by confirming that what they say is recycled REALLY is from recycled sources.  Unifi, which supplies lots of recycled resins and yarns, has an agreement with Scientific Certification Systems to certify that their Repreve yarns are made from 100% recycled content.  Then Unifi’s  “fiberprint” technology audits orders across the supply chain to verify that if Repreve is in a product , that it’s present in the right amounts.  But with this proprietary information there are still many questions Unifi doesn’t answer – the process is not transparent.  And it applies only to Unifi’s branded yarns.

Along with the fact that whether what you’re buying is really made from recycled yarns – or not – most people don’t pay any attention to the processing of the fibers.  Let’s just assume, for argument’s sake, that the fabric (which is identified as being made of 100% recycled polyester) is really made from recycled polyester.  But unless they tell you specifically otherwise, it is processed conventionally.  That means that the chemicals used during processing – the optical brighteners, texturizers, dyes, softeners, detergents, bleaches and all others – probably contain some of the chemicals which have been found to be harmful to living things.  The processing uses the same amount of water (about 500 gallons to produce 25 yards of upholstery weight fabric) – so the wastewater is probably expelled without treatment, adding to our pollution burden.  And there is no guarantee that the workers who produce the fabric are being paid a fair wage – or even that they are working in safe conditions.

One solution, suggested by Ecotextile News, is to create a tracking system that follows the raw material through to the final product.  They assumed that this would be very labor intensive and would require a lot of monitoring (all of which adds to the cost of production – and don’t forget, recycled polyester now is fashion’s darling because it’s so cheap!).

But now, Ecotextile News‘ suggestion has become a reality.   There is a new, third party certification which is addressing these issues.  The Global Recycle Standard (GRS), issued by Control Union, is intended to establish independently verified claims as to the amount of recycled content in a yarn. The GRS provides a track and trace certification system that ensures that the claims you make about a product can be officially backed up. It consists of a three-tiered system with the Gold standard requiring products to contain between 95 percent to 100 percent recycled material; the Silver standard requires products to be made of between 70 percent to 95 percent recycled product; and the Bronze standard requires products to have a minimum of 30 percent recycled content.

And – we think this is even more important –  in addition to the certification of the recycled content, the GRS looks at the critical issues of processing and workers rights.  This new standard holds the weaver to similar standards as found in the Global Organic Textile Standard:

  • companies must keep full records of the use of chemicals, energy, water consumption and waste water treatment including the disposal of sludge;
  • all prohibitied chemicals listed in GOTS are also prohibited in the GRS;
  • all wastewater must be treated for pH, temperature, COD and BOD before disposal;
  • there is an extensive section related to worker’s health and safety.