Why Clothes Wrinkle
Permanent Press: Facts behind the Fabrics
Why clothes wrinkle and how to stop clothes from wrinkling have befuddled people from the time when mirrors were invented. The world of fabrics is littered with many incorrect myths about what causes fabrics to wrinkle and what to do about it. Let’s take a journey together through all the wrinkles of fabric lore to see what we can do about removing wrinkles from clothing.
Why do clothes wrinkle? The two primary causes of wrinkling in fabrics are water moisture and heat. Heat and moisture can remove wrinkles (think ironing and steaming hanging clothes), but they are also the leading causes of that ferociously wrinkled organic cotton shirt. As we’ll see, many other factors can contribute to wrinkled clothing and there is much that you can do to reduce wrinkles that will also reduce the total amount of energy that you will invest in your clothing over their life cycle from when you first go clothing shopping until you are finally ready to send it to the thrift shop, homeless shelter or recyclers.
Which fabrics are more prone to wrinkle? Sometimes it seems as if an organic cotton shirt will sprout contact wrinkles if you just look at it and crinkle your nose while a polyester dress can survive a train wreck and still be ready for a night on the town. Generally, clothes using fabrics made from natural cellulose – cotton, hemp, linen (flax) – are the most prone to wrinkle. Clothes made from regenerated cellulose – bamboo, rayon, Tencel / lyocell, Modal – or from regenerated plant protein – soya, Ingeo – are less likely to wrinkle and wrinkles are easier to remove. Animal fibers – wool, alpaca, cashmere – are generally the least likely to wrinkle. Silk tends to fall in the middle category of wrinkle-ocity.
But, this doesn’t mean that just because a favorite organic cotton skirt is made from organic cotton or hemp that it is going to have more wrinkles than Shar Pei puppies. The tendency of a garment to attract or repel wrinkle is affected by many qualifications such as: weave – knits are less likely to show wrinkles than woven fabrics; fiber blends – wrinkles will easily fall out of a woven yoga top of 95% organic cotton blended with 5% lycra (spandex); quality of fibers – other factors being equal, high quality long staple organic cotton fibers are less likely to wrinkle than lower quality conventionally grown short cotton fibers; quality of manufacturing – a dress of tightly woven, high thread count cotton finished with tightly sown seams will last longer, look better and often require less ironing than a low quality garment; fabric finishes – this is tricky as chemical fabric finishes can be added during manufacturing or during laundering that will reduce the propensity for wrinkling, more about this later; and laundering – which can make all the difference between having your clothing look like the surface of the moon during a solar eclipse or the smooth, shiny backside of a new baby … well, maybe not the best metaphor but you get the idea.
Why do some fibers wrinkle more than others? The differences are in the structural and chemical natures of the fibers that make the fabrics. Let’s quickly first look at how the chemical nature of fibers affect how they respond to wrinkling.
Polymers are the key to understanding wrinkling. Polymers form the basic structure of many fibers which form fabrics. The cellulose found in cotton, bamboo, hemp and linen flax and the proteins that comprise the new eco-fibers Ingeo and soya are natural polymers. Nylon and PET (PolyEthylene Terephtahalate) are examples of synthetic polymers that have been used in clothing. Polymers help hold fibers together and give stability to fabrics.
The energy in heat, whether the heat comes from hot water during washing, hot air in a clothes dryer or even body heat, weakens the covalent bonds that bind polymers together but different polymers of different fibers have different transition points at which the bonds weaken. The polymers of natural cellulose fibers such as cotton, hemp and flax, which is used to make linen, have a much lower transition level and therefore require less heat energy to break the stable covalent bonds than nylon, polyester or regenerated polymers of bamboo, rayon, Tencel / lyocell, Modal, or Ingeo which means that they wrinkle more easily.
This transition point where a polymer’s covalent bonds become weaker is also known as the “glass transition temperature.” An interesting research paper by J.M. Maxwell at the University Of Melbourne, Australia, found that cotton fibers pass through a glass transition at about 72 degrees F (22C) at a relative humidity of 78% which shows the connectedness between heat and water for fabric wrinkles. Different types of fibers have different glass transition temperatures with natural cellulose fibers such as organic cotton, hemp and linen on the lower end of the spectrum making them more susceptible to wrinkling. Research from other sources suggests that moisture and humidity also lower the glass transition temperature, at least for natural cellulose fibers.
Heat is only half of the wrinkle equation. Heat’s partner in growing or removing wrinkles in clothes is water moisture. Using a scanning probe microscope, Maxwell found that water moisture caused cotton cellulose fibers to swell and soften making it easier for the fibers to move and change shape which are all part of the wrinkling or wrinkle removing processes. These are the chemical processes involved in wrinkles.
Mitsuhiro Fukuda of the Textile Materials Science Laboratory at Hyogo University has researched the “dimensional stability” like wrinkling caused by moisture on hydrophilic and hygroscopic fibers such as cellulose and cellulose derivatives (regenerated cellulose). Fukuda documents that a 1% increase in a fiber’s moisture content causes a decrease of about 10 degrees C in the glass temperature for many polymer fibers. The lower the glass temperature of a fiber then the more likely that the fabric will wrinkle.
The structural factors in natural cellulose fibers involve fiber fibrils which are bunches of cellulose chains all lined up together and twisted together into threads that are woven or knit into clothes. The cellulose fibers are held in place through chemical bonds between hydrogen atoms across cellulose fibers. Both heat and water weaken these hydrogen bonds which help keep the fibers in fabrics together and this can happen during washing, drying, while wearing (your skin releases a lot of heat and moisture even if you aren’t sweating), or even while hanging in a closet during a hot, humid day.
To see how wrinkles develop in your cotton, hemp or linen clothing, look through a microscope at the fabric threads and you will see lots of rough little fibers that stick out from the woven threads and become intertwined with other fibrils from other threads. During laundering or even during wearing on warm, humid days, the heat and moisture help weaken the chemical bonds helping to hold fibers in place and the moisture softens the fibers and allows them to slide around more easily. When the fabric dries and cools, the rough little fibers become intertwined with other fibers in different locations and the chemical bonds reform and give rise to the wrinkles. This is why those natural cellulose fiber fabrics have a greater propensity to wrinkle.
Regenerated cellulose fibers, such as bamboo, Tencel / lyocell, Modal, and rayon, are more immune to wrinkling than natural cellulose fiber clothing for two reasons. First, they tend to have a slightly higher glass transition level. Second, regenerated cellulose fibers are born by being shot from a spinneret head into a chemical bath which gives the fibers a smooth surface without small fibers sticking out to snare and become tangled with other fibers during washing or wear.
Fabric weaves and wrinkling. The type of fibers, the temperature and the moisture absorbed by a fiber all contribute to fabric wrinkling, but wrinkling is also influenced by the type of weave and construction of fabrics. Generally, loosely woven fabrics are more susceptible to wrinkling than tightly woven fabric. A high thread count, tightly woven cotton shirt or bed sheet will tend to wrinkle less than a low thread count, loosely woven cotton shirt or bed sheet. The tight weave tends to hold the threads and therefore the fibers in place without as much freedom to move around and give rise to wrinkles.
Knit fabrics tend to wrinkle less than woven fabrics because of the inherent elasticity of a knitted fabric compared with a woven fabric.
Blended fabrics and wrinkling. Stretch woven clothes, which are typically 90% to 96% natural fibers such as cotton blended with 10% to 4% spandex / lycra threads, also tend to be more wrinkle-free due to the elastic quality of the spandex / lycra threads. To reduce nasty wrinkles, clothing manufacturers sometimes blend natural fiber fabrics – cotton, hemp, bamboo, rayon, Tencel / lyocell and even silk – with more wrinkle resistant fibers like polyester. There is an ecological case that states that the total lifecycle environmental cost of synthetic clothes made from polyesters can be significantly less than for natural fibers such as organic cotton and hemp. It’s up to eco conscious and health sensitive consumers to decide where their consuming edges really are.
Silk and wrinkling. For such a simple fiber forced out of the lower lip of the silkworm, the processing into fabric and then into clothing is often complex and chemical intensive. Silk clothing manufacturers often use a wide variety of chemical finishes and manufacturer processes to improve the easy care properties of silk including making silk more wrinkle-free. One chemical process for making silk clothing more wrinkle resistant is by bathing silk in “an aqueous solution containing a water-soluble epoxy compound in a catalyst which may be selected from alkali metal or alkali earth metal salts of dicarboxylic acids, tricarboxylic acids, and amino carboxylic acids.”
Another chemical finish for more wrinkle free finish uses glyoxal resin with ethylene urea and a metal-acid catalyst. Machine-washable silks commonly use urethane resins with or without formaldehyde. And, of course, there is nothing on a garment label that gives a clue as to what chemicals that new silk blouse might have been soaked in. To bad clothing isn’t like Campbell Soups that list all their chemical ingredients.
But, silk naturally has a wide variety of wrinkle and care tendencies depending upon what kind of silk it is. Silk crepe de chine, habotai, noil, and charmeuse are generally easy care silk fabrics less prone to wrinkling. Ahimsa silk, also know as Peace Silk because it is made from silkworm cocoons in which the silk worms were not killed, also wrinkles less than other silks.
Wool and wrinkling. Wool does wrinkle and, like other fibers, the propensity to wrinkle depends upon the weave and type of wool. There are basically two categories of woven wool garments: woolens and worsteds. The distinction between the two categories of wool garments depends upon how the wool fibers are prepared which results in different degrees of snugness in the weave. Woolens are more loosely woven and more prone to wrinkling while worsted wools are more tightly woven and more resistant to wrinkles.
Wool will wrinkle like clothes made from cellulose fibers for most of the same reasons – heat and moisture affecting the glass temperature of the fibers and allowing hydrogen bonds in the fiber molecules to disconnect and reconnect to create wrinkles.
Wool is more wrinkle-resistant and recovers more quickly from wrinkles because of the more elastic nature of wool fibers. The elastic filaments and viscoelastic properties in wool fibers help the fiber stretch and then return to its original state when the force which contorts the fabric into a wrinkle is removed. Low Friction between the yarns in wool fabrics also helps wool garments recover quickly from being wrinkled back to their original state. Wool clothes will wrinkle when the wrinkled state is held for a long period of time in a hot and humid environment.
Wrinkle wrap up. All natural fibers – and synthetic fibers also – have a greater or lesser propensity to wrinkle and the twin enablers that encourage wrinkles are heat and moisture. Both heat and moisture help break weak molecular bonds that bind fibers to each other within fabrics. This allows fibers to shift within the fabric and to be reshaped by other forces such as laundering or wearing clothes in hot, humid conditions. When the temperature is lowered and the moisture dried out, the fibers reform new bonds which give the fabric a wrinkled look.
A fiber’s wrinkle destiny is affected by other factors also such as the type of weave, thread count and tightness of weave, and fabric quality.