The real reason your washing machine has a window, and your dishwasher doesn't

You've probably stood in front of your washing machine at some point, watching your clothes tumble around like you're waiting for the world's most boring movie to get good, but here's the thing: that little window isn't there just for your entertainment. It tells the story of two very different appliances addressing very different problems, and the engineering logic behind each choice is more interesting than you might think.

A story of two inventions
The washing machine and the dishwasher both came along at the same time. James King, an American inventor, introduced a hand-cranked washing machine in 1851. A year earlier, Joel Houghton had already patented a primitive device for washing dishes, but from that point on, they took very different roads, dictated by what each machine had to do and, just as importantly, what users needed to see.

For a long time, the washing machine's design had an inherent visibility. In early top-loading models, you could see right in from the top. Clothing moves unpredictably, fabrics get bunched, water levels matter, and a tangle of clothing in the middle of a cycle can be a damaged garment or a machine that just stops working altogether. Monitoring was no luxury. It was much needed. When front-loading machines first became available to the public in the mid-20th century, engineer John Chamberlain’s automatic model included the signature porthole window specifically because users still needed to see what was going on inside. That room for observation had been baked into laundries for nearly a hundred years.


Why dishwashers remained opaque
The dishwasher had other ideas right from the go. Josephine Garis Cochran, who patented a more functional pressurized version in 1886, was designing for wealthy households that wanted dishes cleaned without servants handling them. Visibility was not provided. In fact, it worked against it.

According to a 2025 study published in Frontiers in Psychology, objects presented in untidy or visibly soiled states were consistently rated lowest in aesthetic preference across categories of household and kitchen items; which goes some way to explaining why a visible window on a dishwasher would work against, rather than for, the appliance. There’s a heat issue, too. Dishwashers need to maintain consistently high temperatures to properly sanitize your dishes, and glass panels can reduce thermal retention, making the cycle less efficient and the appliance more prone to heat loss and leaks in your kitchen.

The design psychology of transparency
According to a study published in the Journal of Engineering Design, a broader design principle is at stake here. Transparency in product design can be a trust signal, but only if the view is reassuring. Through a window in the washing machine, you can see if your $200 cashmere sweater has survived. That's reassuring. A dishwasher window with last night's pasta sauce orbiting your plates like a greasy solar system? Not really.

The result is two machines that look entirely different, not because of arbitrary aesthetics, but because each window, or lack of window, reflects precisely what the user needs from that machine.

What it says about our design practices
For a generation that has grown up with the expectation of transparency from technology, whether it’s watching your package move across a map in real time or seeing your Spotify Wrapped data pop up, the idea that sometimes opacity is the smarter design choice feels counterintuitive. Your dishwasher has been arguing that point for more than a century. Some processes are better trusted than seen.

That little porthole window, next time you're waiting for your laundry? It's not just nostalgia. It’s the whole story of how we learned to live with machines that do the work we don’t want to do.