Pulling a beloved wool sweater out of the dryer to find it’s half the size it was when you put it in can be frustrating. It can leave you wondering, why does wool shrink when you wash it? And how do you wash wool if you don’t want it to shrink?
Wool can shrink in the dryer or washer because of the heat and movement. Wool fibers are made out of protein scales. The combination of heat and movement makes the scales expand and catch on each other, which binds the fibers closer together. The closer the fibers get, the more the wool shrinks.
Modern wool garments are sturdier than ever. Now, we can treat wool to make it easier to wash without shrinking it. This guide will show you how to wash wool without shrinking it and what to do if you’re trying to shrink wool on purpose.
Does 100% Wool Shrink?
100% wool can shrink if you put it in the right environment. Pure sheep’s wool is made entirely of animal protein. Each strand is coated in tiny, sharp scales. On a sheep, these scales all point in the same direction, so they don’t tangle. They’re also covered in a wax called lanolin which protects the sheep’s skin and keeps the wool from shrinking or tangling.
However, the processes that turn that raw sheep wool into threads, yarns, and fabrics remove the lanolin and stretch and twist those protein scales until they are pointing in every direction. That stretching and twisting make it easier for the scales to overlap and hook onto each other.
When you add heat and motion to the already distressed fiber, the scales latch onto each other. Individual fibers bind together, pulling the whole garment tighter together, shrinking it.
If a fabric or garment is 100% wool, there are no other fibers to stop the wool from pulling together. This is why most 100% wool garments recommend handwashing or dry cleaning rather than machine washing. You should never put 100% wool in the dryer unless you are intentionally shrinking it.
How Much Does Wool Shrink?
Wool can shrink down significantly from its original size. Garments you throw in the dryer can shrink two or three sizes easily. However, there are multiple factors that determine how much your wool will shrink.
The amount of heat and motion impacts how much the wool shrinks, as well as the condition of the fiber. The more heat and motion there is, the more the wool will shrink. Heat by itself won’t shrink the wool, so the less motion you use, the less the wool will shrink.
The motion also felts the wool. Felting changes not just the size of the wool but also the texture. Agitation makes the scales on the wool fibers rub together. The more they rub, the closer they lock together, making a dense, fuzzy fabric: felt. Felting shrinks wool down, and once the wool is felted, you cannot un-felt it.
This is why if you accidentally throw a wool sweater in the washer, it might shrink a little, but if you toss it in the dryer, it will shrink much more.
The type of wool also changes how much it will shrink. The longer and smoother a wool fiber is naturally, the more heat and agitation it takes to felt and shrink.
Merino sheep, one of the most common sheep breeds, have fairly long wool fibers without much natural crimp. It takes longer to shrink merino wool than shetland wool, which has more crimp and shorter fibers. The more a wool fiber naturally curls in on itself, the more it will shrink up.
Most commercial wool garments and fabrics are merino wool. The fabric label or garment tag should tell you if it is another type of wool. If it doesn’t specify, assume it is merino wool and that it will shrink fairly easily.
Does Wool Shrink When Washed?
Wool can shrink when you wash it if you don’t follow the advice on the fabric tag or label. The way you wash wool is what determines if it shrinks and how much it shrinks.
Water isn’t what makes wool shrink. You can get wool wet without damaging it as long as the water is room temperature or cooler. The problems arise when the wool is agitated in a hot environment.
You can handwash any wool in cool water, but only some wool can go in the washing machine. Even in cool water, the agitation of the washing machine can shrink the wool. The shrinkage isn’t necessarily permanent—more on that later—but it’s best to avoid putting wool in the washer unless it is superwash wool.
Superwash wool is specially treated wool that won’t shrink or felt in the washing machine. The manufacturer will either coat the wool strands or they will chemically remove the points on the scales. Both methods make it harder for the scales to catch on each other, which prevents shrinkage.
The soap you use can also damage wool in the wash. Enzyme-free detergent or soap is the only kind of cleanser that is safe for wool. If there are enzymes in your cleanser, they will destroy the proteins that make up the fiber. The more damage to the proteins, the more easily the scales interlock and shrink the fiber. Plus, the enzymes can eat holes through the fabric.
Does Wool Shrink in the Dryer?
Wool shrinks in the dryer, even if the manufacturer chemically treated it to withstand the washing machine. Even on a low-heat setting, the dryer uses heat and movement to dry your clothes.
Minimizing heat and spinning or tumbling will minimize shrinking. Spinning or tumbling wool without any heat might felt the wool, causing shrinkage, but it won’t be as severe as if you add heat at the same time.
The coating that protects superwash wool from damage in the washer is not enough to protect wool from the dryer. The coating does more against agitation than it does against heat. However, the more motion and heat a superwash wool garment gets, the faster the superwash treatment wears out.
If you put a superwash wool garment in the dryer for a few minutes, it might not shrink very much. However, the more you dry it, the more it will shrink. Untreated, non-superwash wool will shrink even faster.
Air-drying your wool garments is much better for them. Gently press out any excess water with a clean towel, then reshape the garment to its original size and let it dry flat. This method will prevent shrinking, felting, and warping in your garments.
Does Wool Shrink When It Gets Wet?
Water alone will not shrink wool. Wool expands slightly when you submerge it in water as the fiber absorbs the water. It will return to its original size as it dries as long as you don’t add heat or motion.
Hot water can shrink wool, but only if you also agitate the wool. Heat makes the protein scales more susceptible to catching, but they won’t catch unless there is some movement that forces them to rub together.
The combination of heat and movement causes the most shrinkage because the heat makes the fibers expand and the scales lift, and the movement brings the fibers into contact with each other.
Water can also expand the fibers, but they will return to their normal shape and size when they dry if there isn’t any additional interference. Think of it this way: rainfall doesn’t harm sheep, the source of the wool. Sheep get wet and dry off all the time without changing the shape or size of their coats.
Wool is more delicate when it is wet than when it is dry. That’s the reason cool or lukewarm water is best for washing it. The hotter the water, the more fragile the fibers will be. The more fragile the fibers are, the easier it is for them to tangle and shrink.
If you get caught in the rain in a woolen garment or your feet sweat while you’re wearing your favorite wool socks, there’s no need to panic. That water alone isn’t going to harm the fabric. Make sure to gently squeeze out the water with a clean towel and lay it out in its original shape to air-dry. It will be good as new when it dries.
Does Merino Wool Shrink?
Merino wool does shrink. Merino is one of the most common types of wool for clothing and textiles. It is easy to dye and has a long fiber that makes it soft enough to wear next to your skin.
Merino wool does not felt as easily as other types of wool, but it will shrink if you expose it to heat and agitation. A lot of merino wool garments are superwash, which makes them more durable. However, these fabrics are still prone to shrinking in the dryer.
Do Wool Blends Shrink?
Wool blends can shrink. How severely they shrink depends on how much wool is in the blend. If the wool content is higher than 50%, you can expect about as much shrinkage as with 100% wool.
When a blend has less than 50% wool, the other fibers in the fabric will help keep the wool fibers from blending. A 5% wool blend will usually shrink far less than pure wool. However, if the other fibers are also prone to shrinkage, your garment could get smaller anyway.
Other animal fibers tend to shrink the same way as wool does, as they are made from similar protein structures. Plant fibers are usually less likely to shrink, and man-made and acrylic fibers tend to shrink least of all.
You should always launder a garment according to the most delicate or picky fiber it has. It might be tempting to treat a wool/nylon blend the way you’d treat nylon, but the garment will last longer if you treat it like 100% wool.
Even if your fabric blend doesn’t shrink in the wash, using a washer or dryer setting with high heat and high agitation can damage a wool blend. Heat can wear out the elasticity of many fibers, including acrylics and nylons.
How to Shrink Wool (On Purpose!)
Sometimes, shrinking wool is exactly what you want to do. Maybe the cuffs on your favorite wool sweater are stretched out, or the wool cap you wore every day of winter is starting to sag.
You can put a damp wool garment in the dryer on the lowest heat setting for 3 to 5 minutes to shrink it slightly. However, you will have more control over the process if you shrink the wool by hand.
Fill a large bucket or a sink with hot water and submerge the garment you want to shrink in the water. Move the garment around in the water, swirling it gently for a few minutes. Then, pull it out, squeeze out the excess water, and lay it flat to dry.
You can use your hands to shape it as it dries, spreading out areas you want to be larger and pulling in places you want to shrink up. For even more control, you can use a hairdryer on its lowest heat setting to dry the parts of the garment you want to shrink the most.
Using a hairdryer instead of a clothes dryer lets you see how much the fabric is shrinking as you go. This gives you more control and means you are less likely to shrink the fabric too much or accidentally damage your garment.
Does Wool Shrink Permanently?
Unless the wool has felted, the shrinkage is probably not permanent. You might not be able to get your garment back to its original size if the shrinking was severe. However, there are ways to get the protein scales to loosen to help undo the damage.
Wool has memory, meaning the fibers will always try to return to their normal length even if you stretch them out, crumple them up, or tangle them. This property is one of the reasons wool is a useful fiber for clothing and other textiles.
To activate a wool garments’ memory, you will need to open the fibers back up and loosen the grip they have on each other. Once the grip is looser, the fibers will start to bounce back to their original shape and size, which will restore the garment to its original size.
Opening the fiber back up and loosening the scales is easy to do with water, hair conditioner, and patience.
Human hair is made of similar proteins to wool fibers. Hair conditioner works by smoothing the protein scales in human hair, so when you soak a wool fabric in water and hair conditioner, you get similar results. The water opens up the fibers and lets the conditioner in. The conditioner smooths the protein scales and helps them lay flat instead of sticking out.
To un-shrink your wool, soak it in a solution of water and approximately ⅓ to ½ cup of hair conditioner for 15-20 minutes. Then, gently squeeze out the excess water, and lay the garment out to dry.
While it’s wet, reshape and gently stretch the garment to the size that you want it. As it air-dries, the newly-separated fibers will return to their original length as much as possible.
However, if the wool felts when it shrinks, the conditioner trick won’t do much good. Felting is a permanent process. Getting felt wet and stretching it might give you a few more inches of length, but it will not restore the wool to the original size.
Does Dry Cleaning Shrink Wool?
It is possible for dry cleaning to shrink wool a little bit, but the greater danger is that the process will damage the fibers and shorten the lifespan of the garment.
Dry cleaning isn’t actually dry. It doesn’t use water, but it does use liquid cleansers, and more importantly, heat and motion. The machine that dry cleaners use agitates and heats garments. While professional cleaners know how to be gentle with wool to minimize shrinkage, it is still possible.
More importantly, the solvents dry cleaners use are usually too harsh for wool. Wool is an animal fiber, and the enzymes and chemicals in a professional-grade cleanser can easily break down the proteins that make the fiber.
The occasional dry clean won’t immediately ruin your expensive wool overcoat, but you should minimize how frequently you take wool clothes to the cleaners.
How to Wash Wool Without Shrinking It
Wool is naturally porous, so it doesn’t hold odor or bacteria easily. The further away from your skin, a garment is the less frequently you’ll need to wash it. Wool socks might need washing between each wear, but a sweater you wear over another layer or a wool overcoat will need far fewer washes each season.
When you do need to wash your woolen garments, you can dry clean them, or you can do it safely and inexpensively at home.
The best way to make sure you don’t accidentally shrink your wool is to gently handwash it in cool water with mild detergent and lay it flat to dry, even if it is superwash. This process minimizes movement and eliminates heat.
However, many modern wool fabrics are safe to put in the washer as long as you use cool water and a delicate cycle. You need a combination of heat and agitation to shrink wool. These superwash garments won’t shrink, but they might wear out faster than if you handwash them.
Always check the garment tag or fabric label before you wash wool. It will tell you whether or not the wool is safe to go in the washer. Never put wool in the dryer unless you are shrinking it intentionally.
When you wash your woolens in the washing machine, put them in a lingerie bag or a soft pillowcase first. The extra barrier will help prevent felting. Inside a bag, your wool clothing won’t rub up against all the other clothes in the wash. It will rub against the bag, but the extra protection can prolong the life of the wool.
Conclusion
While you shouldn’t toss all your cashmere and merino sweaters into the washing machine, you don’t have to worry that they’ll shrink up every time they get wet. As long as you avoid heat and vigorous motion, you can keep your woolen garments in the right size and shape for years to come.
Have you ever accidentally shrunk wool clothing? Let us know how you handled it in the comments!