Pre-washing dishes is one of those divisive things about life at home. If you're secretly (or not so secretly) a pre-rinser, it's because you think it's the only right way to do it, and that not pre-rinsing is gross/dirty/lazy/doesn't work/what-have-you. I know because I'm one of them. I grew up with a dishwasher that really didn't get dishes clean on its own, so pre-washing became my practice. But I recently discovered something that has me rethinking my pre-washing ways.
I've heard the warning that you need bits of food on your dishes in the dishwasher to swirl around and help get the grime off of the dishes. Like, the food acts as an abrasive agent in the dishwasher? It sounded strange to me and not just a little dirty. I'll abrade my plates myself and let the dishwasher to do the heavy disinfecting, thank you, I thought to myself.
But left-on-food does lead to cleaner dishes in a different way. Here's an explanation from Good Housekeeping about how that works (turns out it's related to the detergent):
"The makers of the dish detergent Cascade discourage customers from pre-washing or rinsing dishes because it actually inhibits the cleaner from working. 'Enzymes in Cascade detergent are designed to attach themselves to food particles,' the Wall Street Journal reports. 'Without food, the enzymes have nothing to latch onto, says P&G.'
"In other words, your precious detergent just might rinse away before it has time to do anything if your dishes are gunk-free."
But with modern dishwashers, there is another compelling reason to stop short of making your dishes look clean before putting them in the dishwasher, one that has me rethinking my habit: The sensors in the dishwasher may think that already-cleaned plates are cleaner than they really are and may automatically cut the wash cycle short.
Consumer Reports puts it succinctly: "If you've already rinsed off much of the muck, the sensor misreads the dishes as already fairly clean."
This scared me into reconsideration because, as I said, I count on my dishwasher to wash my dishes so much better than I could by hand. Instead, it turns out, starting with dirtier dishes will give me cleaner ones.
So I've started putting dishes in the dishwasher dirty. My dishwasher does a perfectly good job of cleaning them. Another bonus: It's very clear when the dishwasher has dirty dishes; no one's accidentally putting dirty dishes in the washer that's already run and no one's *shudder* putting not-run dishes back in the cupboards.