Why Do Clothes Shrink in the Wash?

Many of us are all too familiar with that sinking feeling that comes when we pull a favorite piece of clothing out of the dryer, only to find it has become much smaller than before. There's nothing worse than thinking that you have ruined a favorite sweater or work dress, and it can cause you to instantly blame your appliance. And, while the dryer may be to blame, there are actually several other causes that can make your clothes shrink.

Normal shrinkage of 2 to 3 percent is fairly common for many garments that have not been prewashed, but anything more than this invariably affects the fit. Shrinkage also can account for things like seam puckering, torquing (pull or hang of fabric), and decorative stitching distortion.

In general, clothing fabrics shrink either because the fibers in the yarns and threads actually contract and get smaller, or because the threads and yarns tighten together. Several different processes contribute to these two actions. Learning why some fabrics shrink in the wash will help you prevent the problem and extend the life of your favorite clothes.

Causes of Clothing Shrinkage

There are many forms of fiber shrinkage that occur during the manufacturing process as natural or synthetic fibers are fabricated into cloth. Once a clothing item is sold and in use, however, there are four processes that cause clothing to shrink: felting, relaxation, consolidation, and contraction. While a particular type of fabric can be especially prone to one kind of shrinking, it is often a combination of several types that miniaturizes your clothes.

Shrinkage Caused by Felting

The first type of shrinkage, felting, occurs most often with clothing constructed of animal hair fibers, like wool or mohair, which have microscopic scales along their surface. When exposed to moisture and excessive heat, these scales can collapse and mesh together, causing the fibers themselves to actually shorten in length. This fiber constriction is the main cause of that familiar shrunken sweater syndrome, which can happen easily if a wool sweater is not handled correctly. This particular type of shrinking occurs only with animal hair fibers that have scale-like construction; it does not happen with cotton, linen, or synthetic fibers.

Shrinkage Caused by Relaxation

Relaxation shrinkage happens with a fabric made with organic yarns or threads that have been stretched or put under tension during the weaving process. This makes the fibers temporarily longer, and when the fabric is later washed in warm or hot water, the threads tend to recover their dimensional stability—their natural curliness—which causes the garment to shrink. The fibers do not actually shrink, but they do changes their shape. This type of shrinkage occurs mostly with organic fibers that are naturally curly, such as wool or cotton. Relaxation shrinkage is less dramatic if the garments were prewashed before purchase, as most shrinkage of this type occurs in the first wash/dry cycle.

Cotton and wool fabrics are the most likely to experience relaxation shrinkage.

Shrinking Caused by Consolidation

Another common issue is consolidation shrinkage, which is due to the mechanical beating that the fabrics take during the washing and drying process. Washing clothes is literally a process of battering the fabrics to dislodge dirt, and this action causes the fibers to be softened and compressed, forcing fibers closer together. With each washing, some amount of clothing fiber is torn off and expelled as lint, and this encourages the garment to compress, especially if other shrinkage factors are present.

Shrinkage Caused by Contraction

High dryer heat can also force out the natural moisture that is found in any fiber. Cotton, for example, typically has a moisture content of about 5 percent, while wool has a moisture level of about 17 percent. If either fabric experiences too much heat, it is likely to fall below its natural moisture content, resulting in shrinkage. The reason wool shrinks more readily is that it has more moisture to lose. Cotton also experiences some contraction when subjected to heat, but synthetic fibers, having little or no moisture content, generally do not contract very much.

How Fabric Type Affects Shrinking

In general, fabrics made from natural plant or animal fibers (wool, mohair, cotton, linen, silk, etc.) will be most likely to shrink, which will be exaggerated when a garment is washed and dried at high temperatures. Synthetic fabrics (polyester, nylon, acrylic, etc.) have fibers that are much less susceptible to shrinkage But extremely high heat can shrink even synthetic fibers, though not to the degree seen in natural fibers.

• Wool and mohair: These fabrics are made with animal hair with a scale-like structure, which is most prone to felting. When yarns or fabrics are treated with chlorine or similar chemicals before garment construction, this removes the scales and lessens the likelihood of felting. These fabrics can also be prone to the other three types of shrinkage. Thus, wool is one of the most problematic of all fabrics when it comes to shrinking in the wash.
• Cotton: Fabrics made from cotton are highly prone to shrinking from the relaxation of the tension applied to the fibers during manufacture, which tends to forcefully stretch the curly strands. To a lesser degree, consolidation can also play a role, especially for loose-woven cotton fabrics. Finally, cotton fabrics can contract if they experience too much moisture loss due to high heat.
• Linen: These fabrics are made from flax fibers, which can be subject to relaxation and contraction shrinkage if they are washed and dried at temperatures that are too high.
• Silk: Silk fabrics are made from organic, protein-rich fibers from silkworms. Contraction shrinkage can occur if silk is exposed to prolonged heat and water. With silk, shrinkage doesn't occur because the fibers themselves shrink, but because heat and water cause the fibers to cling together, tightening the weave. Loosely woven silk can shrink as much as 15 percent if washed vigorously in hot water and then subjected to dryer heat.
• Synthetics: Nylon, polyester, and other synthetic fabrics are generally made from manmade fibers created from petroleum derivatives, and these straight fibers generally experience little to no stretching during the weaving process. Hence, synthetic fabrics are much less prone to shrinking than other fabrics, though high heat from steaming or ironing can occasionally cause some shrinkage.
• Knitted fabrics: Fabrics of any type that are knitted rather than woven are more susceptible to shrinkage. This is because the fabrics have more space between yarn strands, allowing for more consolidation as the item undergoes repeated washings.

Prevention

There are ways you can help control shrinkage. One of the biggest: Follow the care labels on clothes. They're purposely designed with the garment's fibers in mind, so if the label tells you to skip hot water or only air dry, you should listen.

It's also a good idea to read any labels before you buy a piece, too. If you're shopping for an item made from natural fabrics like cotton, wool, or linen, pay special attention to any labels that mark the piece as "pre-shrunk." This means the fabric is shrunk before the garment is sewn together, so you can bet on less shrinkage during its time in your closet. Manufacturers have a variety of methods for minimizing post-purchase shrinkage, ranging from treating the yarns and threads with chemicals such as chlorine before weaving. to prewashing the garments after manufacture.

If you're unsure about how a fabric will react to its first wash, it's a good idea to opt for a cold rinse. While cold water won't prevent all shrinkage, it is definitely less damaging to fabric than hot water and can help ease your garment into a regular washing routine. The same thing goes for drying your clothes, as well: Air drying a garment is often your best option, but if you can't do that, use the lowest heat setting on your dryer.

Lastly, consider your washing and drying machines themselves. Any machine that is without a center agitator will be more gentle on clothes and less likely to cause shrinking due to fiber damage and consolidation. If you have a top-loading washer with a center agitator, reduce its impact on your garments by opting for a gentle or hand-wash cycle.

Can I Restretch a Shrunken Clothing Item?

It doesn't always work, but a sweater or other clothing item that has shrunk can sometimes be returned to its former size by soaking it in water mixed with a small amount of baby shampoo, then stretching it out (blocking) to stretch the garment as it air-dries on absorbent towels.

Hanging it up on a padded hanger while wet can also help stretch out a sweater that has shrunk in length. Simple gravity will cause the fabric to stretch as the sweater slowly dries.