Most homes today have a dishwasher, but many people grew up without them. This lack of early childhood dishwasher education can lead to uncomfortable situations, like the time on summer vacation when I put my nephew’s set of prep knives into the machine, causing a still-ongoing family tiff. And what do you do when your wife insists that pots and pans should be hand-washed, even though the dishwasher has a “Pots and Pans” setting?
Let’s get to the bottom of this. Here are some major rules worth considering:
1. Don’t wash (some) pots and pans in the dishwasher.
This depends on what the cookware is made from and/or coated with:
• Aluminum discolors in reaction with dishwasher detergent.
• Cast iron: The common wisdom is not to wash cast-iron pans in a dishwasher. It won’t really harm the metal, but the built-up, baked-on oil coating (seasoning) may be degraded by exposure to dishwasher detergent — which could lead to the formation of rust.
• Non-stick cookware: The rule-makers say not to put non-stick cookware in the dishwasher, but DuPont says that if the coating is genuine Teflon, it’s OK to put it in.
• Stainless steel is generally OK to put in the dishwasher.
I say you can do cast-iron pans in the dishwasher, but apply a thin coat of olive oil to the cooking surface after you take it out, and heat it on the stove for a few minutes to renew the seasoning.
2. Don’t wash (someone else’s) knives in the dishwasher.
Most high-end knife manufacturers are orthodox on this point. They say:
• If you load good, sharp prep knives into the tableware basket along with your forks, spoons and butter knives, collisions that result from the turbulence during the wash cycle can dull the sharp edges. Moreover, if you stick knives point-upward into the basket, you run the risk of stabbing yourself as you continue to load the machine.
The handles — particularly riveted handles — of good knives can loosen when exposed to a dishwasher’s extreme heat and subsequent cooling.
• I do put my good knives in the dishwasher (and have for years without problems). I place them sharp edge-up in the upper basket along a row of tines meant to separate glasses, to prevent banging, and I use my sharpener as needed — that’s what I got it for.
3. Don’t wash fine glasses in the dishwasher.
Here are the risks:
• Delicate stemware can break from rattling.
• Harsh dishwasher detergents can etch glass and cause it to turn cloudy.
I put wine glasses in the dishwasher, but I also don’t have Waterford crystal. Over the years, my guests have broken more glasses than my dishwasher. Through copious research, I’ve learned that the clouding of glass attributed to dishwasher detergent is most likely caused by minerals in the water and/or improper water softening — which is not a problem where I live.
4.Don’t prewash dishes.
Finally, a rule that makes life easier. Just scrape off the big chunks and load the dishwasher. There are some apparently reasonable arguments for this:
• Prewashing is a waste of water and energy. Modern dishwashers and detergents can handle crusty dishes and breakdown most solids.
• Putting dishes that are too clean into a dishwasher can put them at risk. If there’s no food film on the surfaces, the caustic detergent may attack the finish.
5. Don’t wash woodenware in the dishwasher.
Here’s the common wisdom:
• Repeated, lengthy exposure of wooden spoons and cutting boards to hot water opens the grain and causes cracks and warping.
• Glue joints can come apart in the high heat.
There’s risk in exposing wood to hot water, and for that reason I wash my wooden cutting boards by hand. I do wash wooden spoons in the dishwasher that I use for stirring stews and sauces. So far, I have not seen damage beyond the occasional warped handle, which only endears the object to me. But I would not put wooden salad bowls or dark-finished wood utensils in a dishwasher.
6. Don’t use too much dishwasher detergent.
Dishwasher detergents are not all created equal, but most are quite caustic. The acids used to attack dirt and grease can actually wear down ceramic glazes, metallic appliques, and etch glassware.
•Use only the amount of detergent recommended.
•For light loads and dishes that aren’t heavily soiled, don’t fill the dishwasher’s detergent cup to the brim.
•Powdered dishwasher detergents tend to leave dishes cleaner than liquid or tablet types.
•If glassware is coming out of the dishwasher spotty, try using a rinse agent in combination with dishwasher detergent, rather than simply using more detergent.
It’s important to recognize that dishwasher detergent is only one part of the “solution” — and I use the word as if talking about chemistry — for getting dishes clean. If you’re not happy with finished loads, try experimenting with different detergents that might interact more successfully with the minerals in your local water supply and the water temperature. Also keep in mind that “environmentally friendly” dishwasher detergents contain less phosphate than standard formulas, and many eco-formulas are equally effective.
7. Don’t overload the dishwasher.
Dishes won’t get clean if the spray can’t reach every surface. Yes, for efficiency’s sake, you want to run only full loads, but keep in mind that putting too many items in a dishwasher at once can block pathways. Orthodox dish-washers say that it’s not only the number of items but the way you stack them that makes the difference. When I’m helping clean up at my sister’s house, I’ve got to:
• Place only glassware, cups, and bowls — face-down — in the top rack.
• Load dinner plates toward the back of the bottom rack with the “food side” of each dish facing toward the center — only one item between each pair of tines.
• Load big and tall items like cookie sheets at the extreme edges of the bottom rack.
• Load silverware in the basket with the pointy-end of each piece facing upward and the handle down.
At home, I load table forks and knives into the dishwasher basket with the pointy ends down because I don’t like to stab myself, but pointy-end up may result in cleaner silverware, depending on your machine.
Make Your Own Dishwasher Rules
A dishwasher degreases and disinfects with water that’s hotter than would be comfortable for hand-washing. For killing bacteria dead in its tracks, it’s a better option for most items. But when you’re washing dishes at someone else’s house, it’s important to know the rules!
Michael Chotiner is a master carpenter who also has years of experience as a general contractor, remodeling many homeowners' kitchens and installing appliances. Michael writes on his experiences for The Home Depot. To view a range of dishwashers available at Home Depot, including styles referenced by Michael, click here.