Plastics INsight

If you haven’t noticed from our previous posts about dry erase markers and hair dye, we are constantly curious about the world around us. Whether our team is wondering about antioxidants or helping our interns create transparent wood, there’s simply nothing better than learning from the things we see each and everyday. From a young age all the way to adulthood, it’s exciting to learn something new about things we sometimes take for granted.

That’s why we got curious about how dishwasher pods work. Sure, it functions the same as regular liquid or powder dish soap, but they’re oh so convenient! Throw one in right as you start the dishes and the rest is done for you. No measuring, no spills.

But just how do these pods work?

The real secret lies in the outside coating, but first we’ll talk a little bit about how the other parts of the pod. When the first dishwasher was invented by Josephine Cochran in 1886, a new household convenience was born. They’re now a mainstay in most American homes and serve the same function as back then: clean dishes faster and easier than people can do by hand.

Now we’ll take a look at a dishwasher pod from the inside out–starting with the part most people will think about first: the dish detergent. Whether your pods are produced by major players in the industry like Cascade, or from environmentally-friendly companies like Seventh Generation, the underlying chemistry is the same.

How Do Detergents Work?

All detergents act a surfactant; that is, a substance that reduces the surface tension of a liquid that it’s added to. By reducing the surface tension, detergents allow the liquid to wash away debris more easily.

Detergent molecules are partially lipophilic, meaning they bind to fats and lipids, like grease. In addition, detergent molecules are hydrophilic, which allows the detergent to be soluble in water and wash away easily. It’s no wonder this technology has been around for thousands of years!

The Science Behind Rinse Aids

Along with a detergent, most dishwasher pods also contain a rinse aid. Rinse aid is another type of surfactant, but one that aims to reduce the surface tension enough that the tiny water droplets that form on the surface of dishes are rinsed away. When those drops are encouraged to wash away before they naturally evaporate and leave deposits, your dishes are left looking even cleaner!

Finally, we want to talk about the part of the dishwasher pod that got us thinking in the first place: the outside coating. How is it possible to create a product sturdy enough to be shipped, stored, and safely handled by hand, but then dissolve easily when it’s time to wash the dishes?

Polyvinyl Alcohol (PVA) and Dishwashing Pods

That’s where Polyvinyl alcohol (PVA) comes in. PVA is a water-soluble, shelf-stable, synthetic polymer. Creating a dishwasher pod’s outside coating out of this polymer allows the user to store and use these convenient pods knowing that they’ll only dissolve when they contact water. Even better, PVA is only as irritating as the dish detergent held inside, requiring light washing and flushing with cold water if you get it on your skin or in your eyes. It really is a perfect polymer for this task.

We hope you find dishwasher detergent pods as fascinating as we did. We love this example of great science and the way it makes our lives better, even in the most mundane of tasks.

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