What kind of fabric for your new sofa?

11 06 2015

 

We’ve looked at the frame, suspension system and cushioning on a sofa; next up:  fabric.  We consider fabric to be a very important, yet certainly misunderstood, component of furniture.  It can make up 40 – 45% of the price of a sofa.    So we’ll be breaking this topic up into several smaller bite size portions:  after a general discussion of what kind of fabric to choose for your lifestyle,  we’ll look at the embodied energy in your fabric choice (next post), and then finally we’ll take a look at why an organic fabric is better for you (as well as the rest of us).

One thing to remember is that there is much more fabric used in constructing an  upholstered piece of furniture than just the decorative fabric that you see covering the piece – a typical “quality” sofa also uses about 20 yards of decorative fabric, plus 20 yards of lining fabric, 15 yards of burlap and 10 yards of muslin, for a total of 65 yards of fabric!

So what do people look for in an upholstery fabric?

After color, fabric durability is probably top of everybody’s list.  Durability translates into most people’s minds as “heft” – in other words, lightweight cotton doesn’t usually come to mind.  A fabric with densely woven yarns tends to be more durable than a loosely woven fabric.  Often people assume leather is the best choice for a busy family.  We did a post about leather – if you’re at all considering leather, please read this first (https://oecotextiles.wordpress.com/2012/05/22/leather-furniture-what-are-you-buying/ ).    Another choice widely touted is to use Ultrasuede.  Please see our post about this fabric if you’re considering Ultrasuede: https://oecotextiles.wordpress.com/2010/09/08/is-ultrasuede%c2%ae-a-green-fabric/.

Equally important in evaluating durability is the length of the fibers.  Cotton as a fiber is much softer and of shorter lengths than either hemp or linen, averaging 0.79 -1.30 inches in length.  Hemp’s average length is 8 inches, but can range up to 180 inches in length. In a study done by Tallant et. al. of the Southern Regional Research Laboratory,  “results indicate that increases in shortfibers are detrimental to virtually all yarn and fabric properties and require increased roving twist for efficient drafting during spinning. A 1% increase in fibers shorter than 3/8 in. causes a strength loss in yarns of somewhat more than 1%.”[1]    In fact, the US textile industry has  advocated obtaining the Short Fiber Content (SFC) for cotton classification.  SFC is defined as the percentage of fibers shorter than ½ inch.  So a lower cost sofa upholstered in cotton fabric could have been woven of short fiber cotton, a cheaper alternative to longer fiber cotton and one which is inherently less durable – no matter how durable it appears on the showroom floor.

Patagonia, the California manufacturer of outdoor apparel, has conducted  tests on both hemp and other natural fibers, with the results showing that hemp has eight times the tensile strength and four times the durability of other natural fibers.   Ecolution had a hemp twill fabric tested for tensile and tear strength, and compared the results with a 12-oz cotton denim.  Hemp beat cotton every time:   Overall, the 100% hemp fabric had 62% greater tear strength and 102% greater tensile strength. [2]   And polyester trumps them both – but that’s a whole different ballgame, and we’ll get to that eventually.

There is a high correlation between fiber strength and yarn strength.  People have used silk as an upholstery fabric for hundreds of years, and often the silk fabric is quite lightweight;  but silk is a very strong fiber.

In addition to the fiber used, yarns are given a twist to add strength. This is called Twist Per Inch or Meter (TPI or TPM) – a tighter twist (or more turns per inch) generally gives more strength.  These yarns are generally smooth and dense.

So that brings us to weave structure.  Weave structures get very complicated, and we can refer you to lots of references for those so inclined to do more research (see references listed at the end of the post).

But knowing the fibers, yarn and weave construction still doesn’t answer people’s questions – they want some kind of objective measurement.  So in order to objectively compare fabrics,  tests to determine wear were developed (called abrasion tests), and many people today refer to these test results as a way to measure fabric durability.

Abrasion test results are supposed to forecast how well a fabric will stand up to wear and tear in upholstery applications.  There are two tests generally used:  Martindale  and Wyzenbeek (WZ).  Martindale is the preferred test in Europe; Wyzenbeek is preferred in the United States.  There is no correlation between the two tests, so it’s not possible to estimate the number of cycles that would be achieved on one test if the other were known:

  • Wyzenbeek (ASTM D4157-02):  a piece of cotton duck  fabric or wire mesh is rubbed in a straight back and forth motion on a      piece of fabric until “noticeable wear” or thread break is evident.  One back and forth motion is called a “double rub” (sometimes written as “dbl rub”).
  • Martindale (ASTM D4966-98):  the abradant in this test is worsted wool or wire screen, the fabric specimen is a circle or round  shape, and the rubbing is done in a figure 8, and not in a straight line as in Wyzenbeek.  One circle 8 is a cycle.

The Association for Contract Textiles performance guidelines lists the following test results as being suitable for commercial fabrics:

Wyzenbeek Martindale
Low traffic / private spaces 15,000 20,000
High traffic / public spaces 30,000 40,000

According to the Association for Contract Textiles, end use examples of “low traffic” areas where 30,000 WZ results should be appropriate include executive offices, corporate boardrooms, luxury hotel lobbies, suites and guest rooms. Areas of “high traffic” include: single shit corporate offices, waiting rooms, and high traffic hotel lobbies and guest rooms.

Sina Pearson, the textile designer, has been quoted in the Philadelphia Inquirer as saying that 6,000 rubs (Wyzenbeek) may be “just fine” for residential use”[3]   The web site for Vivavi furniture gives these ratings for residential use:

Wyzenbeek
from to
Light use 6,000 9,000
Medium use 9,000 15,000
Heavy use 15,000 30,000
Maximum use >30,000

Theoretically, the higher the rating (from either test) the more durable the fabric is purported to be.  It’s not unusual for designers today to ask for 100,000 WZ results.  Is this because we think more is always better?  Does a test of 1,000,000 WZ guarantee that your fabric will survive years longer than one rated only 100,000 WZ?  Maripaul Yates, in her guidebook for interior designers, says that “test results are so unreliable and the margin of error is so great that its competency as a predictor of actual wear is questionable.”[4]  The Association for Contract Textiles website states that “double rubs exceeding 100,000 are not meaningful in providing additional value in use.  Higher abrasion resistance does not necessarily indicate a significant extension of the service life of the fabric.”

The reason these test results might not be predicative is because there are, apparently, many ways to tweak test results. We’ve been told if we don’t like the test results from one lab, we can try Lab X, where the results tend to be better.  The reasons that these tests produce inconsistent results are:

1. Variation in test methods:       Measuring the resistance to abrasion is very complex.  Test results are affected by many factors that include the properties and dimensions of  the fibers; the structure of the yarns; the construction of the fabrics;  the type, kind and amount of treatments added to the fibers, yarns, or fabric; the time elapsed since the abradant was changed;  the type of  abradant used; the tension of the specimen being tested,the pressure between the abradant and the specimen…and other variables.

2. Subjectivity:    The  measurement of the relative amount of abrasion can be affected by the method of evaluation and is often influenced by the judgment of the operator.  Cycles to rupture, color change, appearance change and so forth are highly variable parameters and subjective.

3. Games Playing:     Then there is, frankly, dishonest collusion between the tester and the testee.  There are lots of games that are played. For instance, in Wyzenbeek, the abradant, either cotton duck or a metal screen, must be replaced every million double rubs. If your fabric is tested at the beginning of that abradant’s life versus the end of its life, well… you can see the games. Also, how much tension the subject fabric is under –  the “pull” of the stationary anchor of the subject fabric, affects the  rating.

In the final analysis, if you have doubts about the durability of a fabric,  will any number of test results convince you otherwise?  Also, if your heart is set on a silk  jacquard, for example, I bet it would take a lot of data to sway you from your heart’s desire.  Some variables just trump the raw data.

REFERENCES FOR WEAVE STRUCTURE:

1.  Peirce, F.T., The Geometry of Cloth Structure, “The Journal of the Textile Institute”, 1937: pp. 45 – 196

2. Brierley, S. Cloth Settings Reconsidered The Textile Manufacturer 79 1952: pp. 349 – 351.

3. Milašius, V. An Integrated Structure Factor for Woven Fabrics, Part I: Estimation of the Weave The Journal of the Textile Institute 91 Part 1 No. 2 2000: pp. 268 – 276.

4. Kumpikaitė, E., Sviderskytė, A. The Influence of Woven Fabric Structure on the Woven Fabric Strength Materials Science (Medžiagotyra) 12 (2) 2006: pp. 162 – 166.

5. Frydrych, I., Dziworska, G., Matusiak, M. Influence of Yarn Properties on the Strength Properties of Plain Fabric Fibres and Textile in Eastern Europe 4 2000: pp. 42 – 45.

6. ISO 13934-1, Textiles – Tensile properties of fabrics – Part 1: Determination of Maximum Force and Elongation at Maximum Force using the Strip Method, 1999, pp. 16.

[1] Tallant, John, Fiori, Louis and Lagendre, Dorothy, “The Effect of the Short Fibers in a Cotton on its Processing Efficiency and Product Quality”, Textile Research Journal, Vol 29, No. 9, 687-695 (1959)

[2]  http://www.globalhemp.com/Archives/Magazines/historic_fiber_remains.html

[3] ‘How will Performance Fabrics Behave”, Home & Design,  The Philadelphia Inquirer, April 11, 2008.

[4] Yates, Maripaul, “Fabrics: A Guide for Interior Designers and Architects”, WW. Norton and Company.

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What kind of fabric for your new sofa?

26 09 2013

We’ve looked at the frame, suspension system and cushioning on a sofa;  next up:  fabric.  We consider fabric to be a very important, yet certainly misunderstood, component of furniture.  It can make up 40 – 45% of the price of a sofa.    So we’ll be breaking this topic up into several smaller bite size portions:  after a general discussion of what kind of fabric to choose for your lifestyle,  we’ll look at the embodied energy in your fabric choice, and then why an organic fabric is better for you as well as the rest of us.

One thing to remember is that there is much  more fabric used in constructing an  upholstered piece of furniture than just the decorative fabric that you see covering the piece – a typical “quality” sofa also uses about 20 yards of decorative fabric, plus 20 yds of lining fabric, 15 yds of burlap and 10 yds of muslin, for a total of 65 yards of fabric!

So what do people look for in an upholstery fabric?

After color, fabric durability is probably top of everybody’s list.  Durability translates into most people’s minds as “heft” – in other words, a lightweight cotton doesn’t usually come to mind.  A fabric with densely woven yarns tends to be more durable than a loosely woven fabric.  Often people assume leather is the best choice for a busy family.  We did a post about leather – if you’re at all considering leather, please read this first (https://oecotextiles.wordpress.com/2012/05/22/leather-furniture-what-are-you-buying/ ).  Another choice  widely touted is to use Ultrasuede.  Please see our post about this fabric: https://oecotextiles.wordpress.com/2010/09/08/is-ultrasuede%c2%ae-a-green-fabric/.

Equally important in evaluating durability as the weight of the fabric is the length of the fibers.  Cotton as a fiber is much softer and of shorter lengths than either hemp or linen, averaging 0.79 -1.30 inches in length.  Hemp’s average length is 8 inches, but can range up to 180 inches in length. In a study done by Tallant et. al. of the Southern Regional Research Laboratory,  “results indicate that increases in shortfibers are detrimental to virtually all yarn and fabric properties and require increased roving twist for efficient drafting during spinning. A 1% increase in fibers shorter than 3/8 in. causes a strength loss in yarns of somewhat more than 1%.”[1]    In fact, the US textile industry has  advocated obtaining the Short Fiber Content (SFC) for cotton classification.  SFC is defined as the percentage of fibers shorter than ½ inch.  So a lower cost sofa upholstered in cotton fabric, even one identified as an upholstery fabric, could have been woven of short fiber cotton, a cheaper alternative to longer fiber cotton and one which is inherently less durable – no matter how durable it appears on the showroom floor.

Patagonia, the California manufacturer of outdoor apparel, has conducted  tests on both hemp and other natural fibers, with the results showing that hemp has eight times the tensile strength and four times the durability of other natural fibers.   Ecolution had a hemp twill fabric tested for tensile and tear strength, and compared the results with a 12-oz cotton denim.  Hemp beat cotton every time:   Overall, the 100% hemp fabric had 62% greater tear strength and 102% greater tensile strength. [2]   And polyester trumps them both – but that’s a whole different ballgame, and we’ll get to that eventually.

There is a high correlation between fiber strength and yarn strength.  People have used silk as an upholstery fabric for hundreds of years, and often the silk fabric is quite lightweight;  but silk is a very strong fiber.

In addition to the fiber used, yarns are given a twist to add strength. This is called Twist Per Inch or Meter (TPI or TPM) – a tighter twist (or more turns per inch) generally gives more strength.  These yarns are generally smooth and dense.

So that brings us to weave structure.  Weave structures get very complicated, and we can refer you to lots of references for those so inclined  to do more research (see references listed at the end of the post).

But knowing the fibers, yarn and weave construction still doesn’t answer people’s questions – they want some kind of objective measurement.  So in order to objectively compare fabrics,  tests to determine wear were developed (called abrasion tests), and many people today refer to these test results as a way to measure fabric durability.

Abrasion test results are supposed to forecast how well a fabric will stand up to wear and tear in upholstery applications.  There are two tests generally used:  Martindale  and Wyzenbeek (WZ).  Martindale is the preferred test in Europe; Wyzenbeek is preferred in the United States.  There is no correlation between the two tests, so it’s not possible to estimate the number of cycles that would be achieved on one test if the other were known:

  • Wyzenbeek (ASTM D4157-02):  a piece of cotton duck  fabric or wire mesh is rubbed in a straight back and forth motion on a      piece of fabric until “noticeable wear” or thread break is evident.  One back and forth motion is called a “double rub” (sometimes written as “dbl rub”).
  • Martindale (ASTM D4966-98):  the abradant in this test is worsted wool or wire screen, the fabric specimen is a circle or round      shape, and the rubbing is done in a figure 8, and not in a straight line as in Wyzenbeek.  One circle 8 is a cycle.

The Association for Contract Textiles performance guidelines lists the following test results as being suitable for commercial fabrics:

Wyzenbeek Martindale
General contract 15,000 20,000
Heavy duty contract 30,000 40,000

According to the Association for Contract Textiles, end use examples of “heavy duty contract” where 30,000 WZ results should be appropriate are single shift corporate offices, hotel rooms, conference rooms and dining areas.  Areas which would require higher than 30,000 WZ are: 24 hour facilities (like transportation terminals, healthcare emergency rooms, casino gambling areas,  and telemarketing offices) and theatres, stadiums, lecture halls and fast food restaurants.

Sina Pearson, the textile designer, has been quoted in the Philadelphia Inquirer as saying that 6,000 rubs (Wyzenbeek) may be “just fine” for residential use”[3]   The web site for Vivavi furniture gives these ratings for residential use:

Wyzenbeek
from to
Light use 6,000 9,000
Medium use 9,000 15,000
Heavy use 15,000 30,000
Maximum use >30,000

Theoretically, the higher the rating (from either test) the more durable the fabric is purported to be.  It’s not unusual for designers today to ask for 100,000 WZ results.  Is this because we think more is always better?  Does a test of 1,000,000 WZ guarantee that your fabric will survive years longer than one rated only 100,000 WZ?  Maripaul Yates, in her guidebook for interior designers, says that “test results are so unreliable and the margin of error is so great that its competency as a predictor of actual wear is questionable.”[4]  The Association for Contract Textiles website states that “double rubs exceeding 100,000 are not meaningful in providing additional value in use.  Higher abrasion resistance does not necessarily indicate a significant extension of the service life of the fabric.”

There are, apparently, many ways to tweak test results. We’ve been told if we don’t like the test results from one lab, we can try Lab X, where the results tend to be better.  The reasons that these tests produce inconsistent results are:

1. Variation in test methods:       Measuring the resistance to abrasion is very complex.  Test results are affected by many factors that include the properties and dimensions of  the fibers; the structure of the yarns; the construction of the fabrics;  the type, kind and amount of treatments added to the fibers, yarns, or fabric; the time elapsed since the abradant was changed;  the type of  abradant used; the tension of the specimen being tested,the pressure between the abradant and the specimen…and other variables.

2. Subjectivity:    The  measurement of the relative amount of abrasion can be affected by the method of evaluation and is often influenced by the judgment of the operator.  Cycles to rupture, color change, appearance change and so forth are highly variable parameters and subjective.

3. Games Playing:     Then there is, frankly, dishonest collusion between the tester and the testee.  There are lots of games that are played. For instance, in Wyzenbeek, the abradant, either cotton duck or a metal screen, must be replaced every million double rubs. If your fabric is tested at the beginning of that abradant’s life versus the end of its life, well.. you can see the games. Also, how much tension the subject fabric is under –  the “pull” of the stationary anchor of the subject fabric, affects the  rating.

In the final analysis, if you have doubts about the durability of a fabric,  will any number of test results convince you otherwise?  Also, if your heart is set on a silk  jacquard, for example, I bet it would take a lot of data to sway you from your heart’s desire.  Some variables just trump the raw data.

REFERENCES FOR WEAVE STRUCTURE:

1.  Peirce, F.T., The Geometry of Cloth Structure, “The Journal of the Textile Institute”, 1937: pp. 45 – 196

2. Brierley, S. Cloth Settings Reconsidered The Textile Manufacturer 79 1952: pp. 349 – 351.

3. Milašius, V. An Integrated Structure Factor for Woven Fabrics, Part I: Estimation of the Weave The Journal of the Textile Institute 91 Part 1 No. 2 2000: pp. 268 – 276.

4. Kumpikaitė, E., Sviderskytė, A. The Influence of Woven Fabric Structure on the Woven Fabric Strength Materials Science (Medžiagotyra) 12 (2) 2006: pp. 162 – 166.

5. Frydrych, I., Dziworska, G., Matusiak, M. Influence of Yarn Properties on the Strength Properties of Plain Fabric Fibres and Textile in Eastern Europe 4 2000: pp. 42 – 45.

6. ISO 13934-1, Textiles – Tensile properties of fabrics – Part 1: Determination of Maximum Force and Elongation at Maximum Force using the Strip Method, 1999, pp. 16.


[1] Tallant, John, Fiori, Louis and Lagendre, Dorothy, “The Effect of the Short Fibers in a Cotton on its Processing Efficiency and Product Quality”, Textile Research Journal, Vol 29, No. 9, 687-695 (1959)

[2]  http://www.globalhemp.com/Archives/Magazines/historic_fiber_remains.html

[3] ‘How will Performance Fabrics Behave”, Home & Design,  The Philadelphia Inquirer, April 11, 2008.

[4] Yates, Maripaul, “Fabrics: A Guide for Interior Designers and Architects”, WW. Norton and Company.





Synthetic fibers and our oceans

18 02 2012

First we heard about the world’s biggest garbage dump – made up of the detritus of our time: plastic bottles, plastic bags, DVD cases  – floating in our ocean. About 44 percent of all seabirds eat plastic, apparently by mistake, sometimes with fatal effects. And many marine species are affected by plastic garbage—animals are known to swallow plastic bags, which resemble jellyfish in mid-ocean, for example—according to a 2008 study in the journal Environmental Research by oceanographer and chemist Charles Moore, of the Algalita Marine Research Foundation.[1]

Just as soon as we’ve had time to digest this news, we discover that the more improbable impact to the oceans from plastic comes from microscopic particles of plastic:   In fact, the mass of plastic the size of Texas often said to exist in the North Pacific is a myth, according to filmmaker Craig Leeson, who is producing a documentary (backed by David Attenborough and the UK-based Plastic Oceans Foundation)  on the spread of plastics in our oceans.   Instead, particles of plastic lurk in our oceans invisibly, in seemingly clear water.

“If you trawl for it with these special nets that they’ve developed, you come back with this glutinous mass — it’s microplastics that are in the water along with the plankton,” he said. “The problem is that it’s being mistaken for food and being eaten by plankton eaters, who are then eaten by bigger fish, and so it goes on, and it ends up on our dinner tables.”[2]

Charles Moore  has found that in some areas, plastic outweighs zooplankton – the ocean’s food base.[3]

It’s not just in the water:  Dr. Mark Browne, University College Dublin, and several colleagues gathered sand samples from 18 beaches on six continents for analysis. It turns out that every beach tested contained microplastics  (particles about the size of a piece of long grain of rice or smaller).  Charles Moore carries a bag of sand from a beach in Hawaii which he had analyzed – and found that it was 90% plastic.

Studies show that this contamination is getting worse – and link it with health conditions in humans including cancer, diabetes and immune disruption.

So how does this tie into our blog topic of textile issues?

It turns out that 80% of the microplastic found in the samples which the scientists collected on the beaches was fibrous:  polyester, acrylic and polyamides (nylon) fibers.  And the scientists are pretty sure the fibers come from fabric.

According to Science:  “Not a single beach was free of the colorful synthetic lint. Each cup of sand contained at least two fibers and as many as 31. The most contaminated samples came from areas with the highest population density, suggesting cities were an important source of the lint.”[4]

In order to test their idea that sewer discharges were the source of these the plastic discharges, the team worked with a local authority in New South Wales, Australia, and found that their suspicions were correct.  Sewage treatment does not remove the fibers.  But where do the fibers enter the waste stream?

Dr Browne and his colleagueProfessor Richard Thompson from the University of Plymouth carried out a number of experiments to see what fibers were contained in the water discharge from washing machines.

According to a study published in September’s Environmental Science and Technology [5], nearly 2,000 polyester fibers can shake loose from a single piece of clothing in the wash.

“It may not sound like an awful lot, but if that is from a single item from a single wash, it shows how things can build up.” [6]

“It suggests to us that a large proportion of the fibres we were finding in the environment, in the strongest evidence yet, was derived from sewerage as a consequence from washing clothes.”

On Cyber Monday last year, outdoor retailer Patagonia took out a full-page ad in The New York Times asking readers to “buy less and to reflect before you spend a dime.” Beside a photo of their iconic R2® fleece jacket, the headline read: “Don’t Buy This Jacket.”

We fully support Patagonia’s message that we should all pause before consuming anything – our consumption patterns are, after all, what got us into this mess.  “But there might be another reason to take a pass on that jacket besides Patagonia’s confession that the process of creating the R2® Jacket leaves behind “two-thirds of its weight in waste” on its way to their Reno warehouse — it turns out that tossing the jacket in the washer causes it to leave behind something else entirely — thousands of tiny plastic threads.” [7]





Buying decisions

16 12 2009

 

In a previous  post (Prosperity Without Growth, 10.27.09), I discussed a paradigm shift in economics and how that seems to be affected by the fact that bigger isn’t necessarily better  –  and how more stuff doesn’t mean you’re a happier person.  Whether you’re an individual or an interior designer, there are some important considerations beyond budget each time you decide to purchase a product, from flooring to fabric.
Obviously the first decision should be: do I/we really need to purchase this product?  Remember the greenest option is not to decide between a virgin widget and a  recycled widget, but between widget/no widget.    Yvon Chouinard, founder of Patagonia, said “the most responsible way to buy clothes is to shop at Goodwill.  And the most responsible way to build is to recycle an old building.”
One issue that we should consider, always, in making a purchasing decision, is that of “true cost”.  That means you should consider the ecological and psychological consequences of choosing one product over another.  The life cycle analyses done by many companies and government-funded studies are all important in helping us make these assessments.  But I certainly am not claiming that’s an easy thing to do – who has the time to slog through these reports?  As an example of what I’m talking about:    using paper cups that are compostable sounds great  – but what about the fact they’re probably made from corn, a monoculture crop that often displaces valuable forests and wetlands, and uses tons of fertilizers which are responsible for dead zones in oceans?  What about the fact that corn is being used for other things, such as a biofuel, contributing to food shortages in poor countries?  Or consider the world’s first LEED platinum building, the Philip Merrill Environmental Center of the Chesapeak Bay Foundation, which has all the most up to date technology to save energy.  But Environmental Building News pointed out that the new building was constructed 10 miles from the original headquarters in downtown Annapolis – meaning that many of the 100 employees who walked or bicycled to work now must drive.  For new office buildings, energy consumption by commuters is double that of buildings.
But  let’s say you do slog your way through feel-good slogans to make a decision which you feel is based on solid evidence.  You’re ready to buy.
For an individual, remember – your purse gives you a lot of power.  In fact, Diane MacEachern founded Big Green Purse to encourage 1,000,000 women to shift at least $1,000 of money they already spend on everyday items to a comparable item which is a better environmental choice.  That totals  an initial $1 billion Big Green Purse impact.  Companies listen when their bottom lines are affected.  So when you buy an eco fabric, the industry notices and is nudged to begin to change their ways.
DesignersAccord_logo_large1-gallery606
The Designers Accord is a global coalition of designers, educators, and business leaders working together to create positive environmental and social impact.  Adopters of the Designers Accord commit to five guidelines that provide collective and individual ways to integrate sustainability into design, which include:
  • working to increase awareness of the importance of using sustainable practices in all products and processes
  • bringing sustainability to all aspects of undergraduate and graduate design programs so that the next generation of designers is able to practice sustainably;
  • codify best practices to achieve the greatest impact
  • influence policy
As an interior designer, involved each day, perhaps,  in the purchase of a wide variety of products (including fabrics) – you have enormous power.  Susan Szenasy,editor of Metropolis magazine,  in a speech at the American Institute of Graphic Arts National Design Conference, put it this way:  ” Think about this for a moment: an interior designer will buy 1,200 ergonomic chairs for one job, while you and I may buy 12 chairs in a lifetime. If each interior designer demanded that the chairs they specify be designed for disassembly, made of non-toxic materials, and their parts not shipped from thousands of miles away where they might be made by semi-slave labor, the contract furniture industry would have to pay attention.”
Daniel Yang, writing on the ethics of design, said:  “Most discussion of ethical design (if mentioned at all) usually revolves around using environmentally sustainable materials, or doing a communications campaign for a non-profit group. Rarely is the relationship between designer, client, and end user questioned. Yet it’s something that nearly every designer is faced with on a daily basis. It’s easy to refuse a client when much of society denounces it, as in the case of Big Tobacco. It’s a lot harder to advocate against a client’s marketing plans when most of the people that end up consuming the product will probably never come back to complain. We pick and choose our battles, but if we retreat from every fight we’ll eventually have nothing left of a professional soul. Erring on the side of the users over the client might cost you your job, but at least your integrity as a designer will be intact. This isn’t an issue of legal liability, but rather an ethical issue of creating the kind of world we want to live in. After all, we are all end-users of products that someone else is designing.

How can the designer be held responsible if the client is approving everything? It’s true that the client is historically the one deciding what functions something will have, because they assume the financial risk of failures. But a designer isn’t a mindless agent producing a product from a blueprint. There may be specifications, but the designer is the one drawing the blueprint. This is where the designer’s role as an expert advisor comes into play. Hopefully, the client hired the designer because of his expertise in understanding how a particular medium functions. It is assumed that he has a body of knowledge that is deeper than the client’s in a particular area. It wouldn’t make sense for the client to seek the designer’s services otherwise. Thus the ethical burden is placed on the designer because the client does not have the expertise that the designer does. The client can plead ignorance but the designer cannot.”

But lest you are disheartened by the above, Susan Szenasy ended her speech by saying:

“So, is there any good news in all of this? Yes. And it has to do with design. Designers today stand on the brink of being seen by society as essential contributors to its health, safety, and welfare. If you—together with the other design professions—decide to examine the materials and processes endemic to your work, as well as demand that these materials and processes become environmentally safe, you will be the heroes of the 21st Century.”





Abrasion testing

18 11 2009

One of the questions we get most often is this:   “what fabric is the best for my sofa”?  We know they’re talking about durability, which I’ll address below, but it’s also important to think about “best” in terms of livability and health concerns.  I mean, you can buy a fabric that has a 1,000,000 WZ test result – it should survive anything you can throw at it – but do you want to live with it?

I have 3  (now grown) sons, and we’ve had assorted (big) dogs, so I totally know why people ask this question.  But to answer in terms of durability is a complicated question to answer because durability depends on several things:  construction of the yarns and the construction of the weave (and tests which include seam slippage, pilling, tensile strength and usage)  are  almost as important as the fiber chosen.  In addition, finishes, furniture design, maintenance, cleaning and usage are variables that affect the life of your fabric.

Cotton as a fiber is much softer and of shorter lengths than either hemp or linen, averaging 0.79 -1.30 inches in length.  Hemp’s average length is 8 inches, but can range up to 15 feet in length. In a study done by Tallant et. al. of the Southern Regional Research Laboratory,  “results indicate that increases in shortfibers are detrimental to virtually all yarn and fabric propertiesand require increased roving twist for efficient drafting duringspinning. A 1% increase in fibers shorter than 3/8 in. causesa strength loss in yarns of somewhat more than 1%.” (1)    In fact, the US textile industry has  advocated obtaining the Short Fiber Content (SFC) for cotton classification.  SFC is defined as the percentage of fibers shorter than ½ inch.

Patagonia, the California manufacturer of outdoor apparel, has conducted  tests on both hemp and other natural fibers, with the results showing that hemp has eight times the tensile strength and four times the durability of other natural fibers.   Ecolution had a hemp twill fabric tested for tensile and tear strength, and compared the results with a 12-oz cotton denim.  Hemp beat cotton every time:   Overall, the 100% hemp fabric had 62% greater tear strength and 102% greater tensile strength. (2)   And polyester trumps them both – but that’s a whole other ballgame.

There is a high correlation between fiber strength and yarn strength.  In addition to the fiber used, yarns are given a twist to add strength. This is called Twist Per Inch or Meter (TPI or TPM) – a tighter twist (or more turns per inch) generally gives more strength.  These yarns are generally smooth and dense.

So that brings us to weave structure.  Weave structures get very complicated, and we can refer you to lots of references for those so inclined  to do more research (see references listed below).

But knowing the fibers, yarn and weave construction still didn’t answer people’s questions – they wanted some kind of objective measurement.  In order to objectively compare fabrics,  tests to determine wear were developed (called abrasion tests), and many people today refer to these test results as a way to measure fabric durability.

Abrasion test results purport to forecast how well a fabric will stand up to wear and tear in upholstery applications.  There are two tests:  Martindale and Wyzenbeek.  Martindale is the preferred test in Europe; Wyzenbeek is preferred in the United States.  There is no correlation between the two tests, so it’s not possible to estimate the number of cycles that would be achieved on one test if the other were known:

  • Wyzenbeek (ASTM D4157-02):  a piece of cotton duck fabric or wire mesh is rubbed in a straight back and forth motion on a piece of fabric until “noticeable wear” or thread break is evident.  One back and forth motion is called a “double rub” (dbl rub).
  • Martindale (ASTM D4966-98):  the abradant in this test is worsted wool or wire screen, the fabric specimen is a circle or round shape, and the rubbing is done in a figure 8, and not in a straight line as in Wyzenbeek.  One circle 8 is a cycle.

The Association for Contract Textiles performance guidelines lists the following test results as being suitable for commercial fabrics:

Wyzenbeek Martindale
General contract 15,000 20,000
Heavy duty contract 30,000 40,000

According to the Association for Contract Textiles, end use examples of “heavy duty contract” where 30,000 WZ results should be appropriate are single shift corporate offices, hotel rooms, conference rooms and dining areas.  Areas which would require higher than 30,000 WZ are: 24 hour facilities (like transportation terminals, healthcare emergency rooms, casino gambling areas,  and telemarketing offices) and theatres, stadiums, lecture halls and fast food restaurants.

Sina Pearson, the textile designer, has been quoted in the Philadelphia Inquirer as saying that 6,000 rubs (Wyzenbeek) may be “just fine” for residential use”(3)   The web site for Vivavi furniture gives these ratings for residential use:

Wyzenbeek
from to
Light use 6,000 9,000
Medium use 9,000 15,000
Heavy use 15,000 30,000
Maximum use >30,000

Theoretically, the higher the rating (from either test) the more durable the fabric is purported to be.  It’s not unusual for designers today to ask for 100,000 WZ results.  Is this because we think more is always better?  Does a test of 1,000,000 WZ guarantee that your fabric will survive years longer than one rated only 100,000 WZ?  Maripaul Yates, in her guidebook for interior designers, says that “test results are so unreliable and the margin of error is so great that its competency as a predictor of actual wear is questionable.”(4)  The Association for Contract Textiles website states that “double rubs exceeding 100,000 are not meaningful in providing additional value in use.  Higher abrasion resistance does not necessarily indicate a significant extension of the service life of the fabric.”

And of course, any company can skew results in their favor.  This is an image I found on Google images, with abrasion test results from a company selling leather motorcycle clothing.  They did say  ” that leather will sometimes score up to 100,000 cycles or so on the Wyzenbeek test, but testing to destruction (over 50k cycles) doesn’t always prove much.”  No comment on these results !

leather-with-lycra-graph

There are, apparently, many ways to tweak test results. We’ve been told if we don’t like the test results from one lab, we can try Lab X, where the results tend to be better.  The reasons that these tests produce inconsistent results are:

  1. Variation in test methods:  Measuring the resistance to abrasion is very complex.  Test results are affected by many factors that include the properties and dimensions of the fibers; the structure of the yarns; the construction of the fabrics; the type, kind and amount of treatments added to the fibers, yarns, or fabric; the time elapsed since the abradant was changed;  the type of abradant used; the tension of the specimen being tested,the pressure between the abradant and the specimen…and other variables.
  2. Subjectivity: The measurement of the relative amount of abrasion can be affected by the method of evaluation and is often influenced by the judgment of the operator.  Cycles to rupture, color change, appearance change and so forth are highly variable parameters and subjective.
  3. Games Playing:  Then there is, frankly, dishonest collusion between the tester and the testee.  There are lots of games that are played. For instance, in Wyzenbeek, the abradant, either cotton duck or a metal screen, must be replaced every million double rubs. If your fabric is tested at the beginning of that abradant’s life versus the end of its life, well.. you can see the games. Also, how much tension the subject fabric is under – the “pull” of the stationary anchor of the subject fabric, affects the rating.

In the final analysis, if you have doubts about the durability of a fabric,  will any number of test results convince you otherwise?  Also, if your heart is set on a silk  jacquard, for example, I bet it would take a lot of data to sway you from your heart’s desire.  Some variables just trump the raw data.

(1) Tallant, John, Fiori, Louis and Lagendre, Dorothy, “The Effect of the Short Fibers in a Cotton on its Processing Efficiency and Product Quality”, Textile Research Journal, Vol 29, No. 9, 687-695 (1959)

(2) http://www.globalhemp.com/Archives/Magazines/historic_fiber_remains.html

(3) ‘How will Performance Fabrics Behave”, Home & Design,  The Philadelphia Inquirer, April 11, 2008.

(4) Yates, Maripaul, “Fabrics: A Guide for Interior Designers and Architects”, WW. Norton and Company.

REFERENCES FOR WEAVE STRUCTURE:

1.  Peirce, F.T., The Geometry of Cloth Structure, “The Journal of the Textile Institute”, 1937: pp. 45 – 196

2. Brierley, S. Cloth Settings Reconsidered The Textile Manufacturer 79 1952: pp. 349 – 351.

3. Milašius, V. An Integrated Structure Factor for Woven Fabrics, Part I: Estimation of the Weave The Journal of the

Textile Institute 91 Part 1 No. 2 2000: pp. 268 – 276.

4. Kumpikaitė, E., Sviderskytė, A. The Influence of Woven Fabric Structure on the Woven Fabric Strength Materials

Science (Medžiagotyra) 12 (2) 2006: pp. 162 – 166.

5. Frydrych, I., Dziworska, G., Matusiak, M. Influence of Yarn Properties on the Strength Properties of Plain Fabric

Fibres and Textile in Eastern Europe 4 2000: pp. 42 – 45.

6. ISO 13934-1, Textiles – Tensile properties of fabrics – Part 1: Determination of Maximum Force and Elongation at

Maximum Force using the Strip Method, 1999, pp. 16.