How chemistry makes your ironing easier

I hate ironing, I’ll do more or less anything to avoid it. So faced with a giant pile of laundry I got easily distracted. I started to wonder why those shirts emerged from the machine looking like a tangled bag of rags. How come the cotton clothes get crumpled so easily? And what’s with easy-iron garments, why don’t they need so much pressing?

Since I’m a scientist I know it is important to understand the theory behind a methodology. And so it became imperative, before unleashing the iron and its board, that I found the answers to these pressing questions.

It turns out that the wrinkles in my shirts are all down to the chemistry of plant-based fabrics. Cotton, linen, hemp and so on are predominantly made of cellulose. Cellulose is what’s known as a polymer because it consists of thousands of glucose molecules joined together to form linear chains. Each glucose subunit is “sticky” because it can bind to neighbouring cellulose molecules via something called hydrogen bonds. Individually, these bonds are very weak, but together they form a strong network that gives the fabric its strength.

These hydrogen bonds are particularly dynamic in that they are forever breaking and then rapidly reforming. As a result, clothes start taking on the shape that they are left in. This isn’t a problem if I get around to putting freshly ironed shirts on a hanger. But it is an issue when I chuck them in a heap on the “floordrobe”. As they sit there in a pile, the bonds break and reform, the clothes take up the new shape of the fabric, and the creases set in place.

Just add water

Things get even worse when water enters the equation (like in the washing machine). Water molecules insert themselves between the cellulose molecules, break up the hydrogen bonds and act like a lubricant, allowing the cellulose molecules to slide over each other. Then, when the fabric dries, the cotton keeps its now wrinkled shape. And that is the state of the pile of shirts that now stands before me.

This is where the hot, steaming iron comes in. The combination of heat and moisture quickly breaks the hydrogen bonds. As I apply these with a bit of pressure, all the cellulose molecules are forced to lie parallel with each other, so flattening the cloth.