Why You Shouldn't Put Travel Mugs In The Dishwasher
Cooking is a great way to create something beautiful and delicious, or to show someone how much you care for them (even if that person is yourself). But there is nothing that will bring you down off the high of a good meal faster than seeing the dishes stacked up in your sink. If you have a dishwasher in that moment, it can be your saving grace, but it can't do it all.
A sink full of plates and glasses can usually get loaded into your standard dishwasher and come out looking spotless. However, there are still plenty of items that you should be washing by hand. Cast iron or non-stick pans can get ruined in dishwashers, wooden spoons can warp and crack, and knives can be damaged or dulled.
Also on that list is your favorite insulated travel mug. While there are some mugs out there that will claim to be dishwasher safe, most are at risk of being damaged when put into the handy kitchen appliance (via Monsieur Coffee).
How dishwashers harm travel mugs
Insulated travel mugs are absurdly versatile for something that is essentially designed to keep liquid separate from its environment as much as possible. They'll keep your drink hot. They'll keep your drink cold. They can be fashion statements. They can help the planet. But they can't go in your dishwasher.
The reason for this, according to Monsieur Coffee, is that the high water pressure and extreme heat cycles can damage their precious vacuum seal — and if the seal is damaged, your favorite travel mug will lose its insulating properties.
Insulated mugs are built with a small chamber inside of a larger chamber that is separated by a small empty gap. The outer and inner chambers are sealed together after all of the air has been vacuumed out of this gap. Having this vacuum next to your coffee or tea keeps it at the same temperature because there are no particles there to conduct the heat away from your drink. This is how your coffee will stay the same temperature in a properly sealed mug even when walking in a blizzard.
However, putting your mug in a dishwasher can damage that seal, allow air into that vacuum, and make it less effective. It's best to simply scrub the interior of your favorite mug down with some warm water and a light dish detergent instead before letting it dry completely.