Science Facts

Why Do Clothes Shrink In Wash? Causes & Solution

Clothes Shrink

Shrinkage is the process in which a fabric becomes smaller than its original size. It usually occurs during the first few washes. The cloth can shrink lengthwise and create problems in fitting into them. Shrinkage depends on fabric, composition, properties, structure, and finishing. Some high shrinkage fabrics, while others are low shrinkage fabrics. High shrinkage fabrics, including natural fibers.

So when natural fibers like these are exposed to moisture and excess heat, the fiber compresses and meshes together. On the other hand, low shrinkage fabrics are usually synthetic and human-made, such as polyester and nylon. Synthetic fibers do not shrink because the washing machine does not get hot enough. So the petroleum-based fabrics remain unchanged in size.

There’s more work needed to be done to prevent shrinkage of natural fibers. These include methods such as submerging the new fabric in water before cutting the garment. So after it has shrunk, the fabric comes to its original size and then can be used to make clothes to control shrinkage in line garments. The best combination of two different fabrics should always be in the same shrinkage time, which means that high shrinkage fabrics work best with similar high shrinkage lining.

Why do clothes shrink in the wash?

In layman’s terms: you do laundry, and it is like controlled chemistry! There are a couple of kinds of fibers used to make clothing: synthetic and natural. In general, synthetics are artificial polymers like polyester, rayon, Kevlar, or acrylic. Their fibers are strings of petroleum-based chemical chains. Synthetics from petroleum products don’t typically shrink in the laundry because the washer and dryer do not get hot enough to mess with their structure.

Natural fibers, on the other hand, come from animals and plants. The fibers of cotton, wool, or silk are naturally curly and tangled. When you want to weave these threads into fabrics, you have to stretch and pull them to make them straight. But if allowed to return to the natural curly state, they will. And scientists have discovered the heat and mechanical energy in laundry machines let them do just that in a shrinkage process.

There are three kinds of shrinkage:

  • Relaxation.
  • Felting.
  • Consolidation.

Relaxation: Relaxing is the immediate release of that stretching and pulling tension left behind from the straightening of the natural fibers. That tension exists on a molecular level and is leftover from the manufacturing process. When tepid or warm water is added to the natural fabric, the warmth will let the fabric swell, reducing the size by about 1 percent.

Felting: Felting shrinkage is when the fibers themselves get shorter. If you magnify wool in an electron microscope, it’s made of tiny scales, just like human hair. According to a paper in the Textile Research Journal, the heat from the washer can expand these scales letting water get between them. Water is slippery, so it reduces the coefficient of friction. And those scales slide together, contracting rootward, like a retracting car or radio antenna!

Consolidation: The third type is Consolidation shrinkage, and it happens in the laundry process itself. The mechanical bouncing action of washer and drier beats up the fibers, curling them back up again. A 2002 study in The Research Journal of Association of Universities for Textiles found the structure of the fabric affects shrinkage.

Denim jeans are tightly woven cotton, so they only shrink slightly, but sweaters are mostly air! So they can shrink as much as 30 percent, according to Popular Science. Even the natural moisture content of the fibers themselves can affect shrinkage: cotton has about 5 percent, wool has about 17 percent. So over-drying can inevitably cause clothing to change shape.

Nazi scientists added plastics to wool to fill in the spaces and solidify the fibers in World War II. Today this continues with manufacturers weaving in non-shrinking synthetics. And chemists inventing new anti-shrinking agents to cover natural fibers and keep them from curling up. Scientists who did write papers on shrinkage were quick to point out: everyone does laundry differently. Water temperature, time, detergent, clothing fibers, and even machine manufacturer all add variables to the laundry at-home science project.

What causes clothes to shrink?

We can break clothing fibers down into three categories – synthetic, plant-based, and animal-based. Each of these fibers has a chemical makeup that will respond to cleaning methods differently, and many clothing garments can be made out of a mix.

Synthetic: Synthetic fibers are polymer chains built out of small units, or monomers, usually derived from petroleum. It includes materials like polyester, nylon, polypropylene, and many more. Most synthetic fibers are hydrophobic or water-hating. It is why they’re often used as outerwear to shed water or underwear to breathe and let moisture escape from the skin. For the most part, these types of materials have no issue with water and don’t shrink when machine washed.

Plant-based: Plant-derived materials contain cotton, linen, and hemp with fibers with chemical structures made of cellulose, which are long polymers of glucose molecules. These types of materials are perfectly fine to clean in your washer at home because the cellulose fibers are polar. Therefore hydrophilic, or water-loving. This quality allows these materials to absorb and release water without any lasting effect on their structure.

Be careful, though, because high temperatures both with washing and drying can potentially warp these materials. For this reason, many clothing manufacturers pre-shrink thread, so you don’t have to worry about it.

Animal-based: Protein-based fibers like silk and wool are a different story. These materials have polar and nonpolar sections arranged in tube-like structures, making the inside hydrophilic and outside hydrophobic. These exteriors are excellent for light exposure to water, like when it rains because it rolls right off. But when things get wet garment is in big trouble because water can eventually break through into the hydrophilic interior, where it sticks around.

This is why wool takes so long to dry once it gets fully soaked. These water molecules cause the interior of the fiber structure to swell. And to accommodate that swelling, the exterior of the fiber has to contract lengthwise.

When the water eventually evaporates, the fibers remain in this shortened configuration, and the sweater is now misshapen or way too small. Regular detergent interacts with the hydrophobic surface, helping transport water into it, causing damage to its structure. A low temperature, short wash time, and mild detergent help reduce stress on fibers to limit the damage.

Conclusion

Keep this in mind, The manufacturer can produce high-quality clothes while assuring customer satisfaction. For example, of the line, top-dresses or skirt is in rayon fabric. The fabric, the lining fabric, should be made with rayon. But as for synthetically made fibers, if the garment line is low shrinkage, the best material for ironing is polyester or other fabric or other synthetic fabric as is.

Shrinkage in the fabrics is negligible. If the garment demands low shrinkage body fabric with high shrinkage, lining fabric, or high shrinkage body fabric with low shrinkage, lining precautions must be taken. Users complain that the lining may come out from where the body fabric shrinks after a few washes.

If manufacturers use polyester or any synthetic fabric for the body and use quaternary fabric for lining, the outer body is the same after a few washes. So manufacturers need to take needful precautions and preaching the high shrinkage.

Frequently asked questions

Does hot water shrink clothes?

Hot water does shrink clothes sometimes. That depends on temperature and cotton quality. Hot water shrinks clothes to their maximum shrinkage capacity after one wash. On the other hand, warm water shrinks them more gradually over multiple washes.

How to Stop clothes from shrinking?

Just make sure to reshape clothes when you lay them to dry, or the wool may dry misshapen. There’s dry cleaning, which saves clothes from any contact with water. If you read “dry clean,” it’s more of a recommendation than necessary when looking at the label. It’s when it says “dry-clean only” that you should do so because these are the clothes prone to shrinkage.

Contrary to what you might think, dry cleaning isn’t dry at all. Instead of using water, this cleaning method relies on perchloroethylene, or “perc,” for short. This chlorinated molecule can’t penetrate protein-based fibers, so it doesn’t cause any shrinkage.

  • Use cold water and avoid the dryer.
  • Remember that natural fiber clothing is made from the parts of living things!

Professional cleaners clean with a mixture of perc and detergent, both of which have specific purposes. Perc is an oil-loving, nonpolar solvent, so it does a great job of lifting non-polar stains from fabric, like that sweat ring around your collar or that greasy spill from lunch. The detergent helps lift any water-soluble stains that the perc can’t interact with on the cleaning method.

After a final perc rinse, the laundry gets spun and tumbled dried, all within the same machine. But a word of caution: Some synthetic fibers can dissolve in dry cleaning solvents. Plants and synthetics are good to go in the water. But protein-based animal fibers will always need some special attention and maybe even dry cleaners. Yet another reason to keep chemical knowledge fresh and clean!


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Sources:

Annis, Patricia, Understanding and Improving the Durability of Textiles. Elsevier. ISBN 978-0-85709-764-4.
“AATCC Test Methods, Technical Manual & Standards”. AATCC Online.
“LP1 Home Laundering: Machine Washing”.

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