Our cars can park themselves, and we can play our favorite music or order things online simply by talking to Alexa. Why is it that we there are still all sorts of clothes on the market that will shrink if not laundered correctly?

Some things are beyond technology—at least if you prefer your clothes to be made of natural fibers like cotton or wool. While science hasn’t found a way to make these natural fibers shrink-proof, it can explain why the shrinking happens. Here’s why.

Please Return Your Cotton Fiber to Its Original Position

It turns out that cotton doesn’t really shrink. Your cotton clothing is made of fabric of threads woven together, which are in turn made up of cotton fibers. Cotton fiber is made up of long molecular chains that are linked end-to-end by hydrogen.

When cotton fibers are spun into thread, which is then woven into fabric, those fibers and the molecular chains making them up are stretch, pulled, and twisted. This stresses the hydrogen holding everything together.

Throw that cotton fabric in the wash and the stress starts to get relieved. The bonds and polymers at the molecular level relax. Your cotton clothes don’t shrink, as much as the thread they are made of returns to its pre-stretched size.

What About Wool?

This is all about science, so it’s time for a quick science experiment. Take a piece of your own hair and pull it through your thumb and finger by the root end. Now, do the same thing from the other end.

It doesn’t slide through your fingers as smoothly, does it?

Your hair is covered with small raised scales. They’re pointed in the same direction, sort of like the tiles on a roof. Wool fibers have scales just like human hair. When wool fibers are processed and woven into fabric, those scales snag each other, and the fiber’s natural alignment is disrupted.

Introducing woven wool fabric to water allows those scales to realign themselves. Heat from the dryer tightens up the contact between the fibers in the fabric. It looks to you like the fabric shrank. Scientists looking at the fiber under a microscope would correct your observation and tell you that the fibers simply returned to their naturally aligned preference.

Shrink-Proof?

You can purchase cotton clothes that are pre-washed, which means material is allowed to return to its “de-stressed” state before sewn into what we wear. Other types of cotton fabric is treated with finishes that help the hydrogen polymer bonds withstand the “return to natural state” transformation of washing.

Some wool fabrics are treated with chlorine, which smooths the scales.

Synthetic fabric fibers don’t absorb as much water as natural fibers like cotton and wool. It’s why they tend not to shrink—or return to a natural state—to be scientifically accurate.

It’s wise to put your pure cotton or wool clothes in the hands of professional laundry and dry cleaning services. They know the science behind keeping your clothes from shrinking—or whatever it is that cotton and wool really do if you try washing them at home.

Some things are beyond technology—at least if you prefer your clothes to be made of natural fibers like cotton or wool. While science hasn’t found a way to make these natural fibers shrink-proof, it can explain why the shrinking happens. Here’s why.

Please Return Your Cotton Fiber to Its Original Position

It turns out that cotton doesn’t really shrink. Your cotton clothing is made of fabric of threads woven together, which are in turn made up of cotton fibers. Cotton fiber is made up of long molecular chains that are linked end-to-end by hydrogen.

When cotton fibers are spun into thread, which is then woven into fabric, those fibers and the molecular chains making them up are stretch, pulled, and twisted. This stresses the hydrogen holding everything together.

Throw that cotton fabric in the wash and the stress starts to get relieved. The bonds and polymers at the molecular level relax. Your cotton clothes don’t shrink, as much as the thread their made of returns to its pre-stretched size.

What About Wool?

This is all about science, so it’s time for a quick science experiment. Take a piece of your own hair and pull it through your thumb and finger by the root end. Now, do the same thing from the other end.

It doesn’t slide through your fingers as smoothly, does it?

Your hair is covered with small raised scales. They’re pointed in the same direction, sort of like the tiles on a roof. Wool fibers have scales just like human hair. When wool fibers are processed and woven into fabric, those scales snag each other, and the fiber’s natural alignment is disrupted.

Introducing woven wool fabric to water allows those scales to realign themselves. Heat from the dryer tightens up the contact between the fibers in the fabric. It looks to you like the fabric shrank. Scientists looking at the fiber under a microscope would correct your observation and tell you that the fibers simply returned to their naturally aligned preference.

Shrink-Proof?

You can purchase cotton clothes that are pre-washed, which means material is allowed to return to its “de-stressed” state before sewn into what we wear. Other types of cotton fabric is treated with finishes that help the hydrogen polymer bonds withstand the “return to natural state” transformation of washing.

Some wool fabrics are treated with chlorine, which smooths the scales.

Synthetic fabric fibers don’t absorb as much water as natural fibers like cotton and wool. It’s why they tend not to shrink—or return to a natural state—to be scientifically accurate.

It’s wise to put your pure cotton or wool clothes in the hands of professional laundry and dry cleaning services. They know the science behind keeping your clothes from shrinking—or whatever it is that cotton and wool really do if you try washing them at home.