Avoid a dishwasher disaster.

Nothing can work some serious wonders in the kitchen like a dishwasher. It's the magical place where a precarious pile of dirty dishes goes in and comes out squeaky clean, time and time again. It gets put through the ringer every holiday, tailgate, and bake sale season, yet still keeps delivering Grammy-worthy performances.

Until. That moment when we pull out our favorite travel mug or milk glass bowls, and our dishwasher has betrayed us. It's a sad mistake we all make once or twice, but it's also one that can be easily avoided. Turns out, there's still very much a place for hand-washing in the kitchen, and here's a definitive list of things that you should never, ever, put in the dishwasher.

Cast-iron skillets: Your cast-iron skillet is such a game-changer when it comes to gooey cobblers and classic cornbread that it'd be a real shame to lose it. A sin, even, in our not-so-humble opinion. The seasoning on a cast-iron skillet is what makes it so unique, and the dishwasher can degrade the coating and eventually lead to rust.

Chef's knives: A sharp chef's knife can make or break your dinner prep, and putting it in the dishwasher dulls the blade over time. Instead of throwing your best guys into the machine, keep them in tip-top shape by hand-washing.

Insulated mugs & cups: Your favorite and most trusted travel mug might not be so airtight after a couple visits to the dishwasher. The same goes with plastic or metal insulated cups. The insulated airspace that keeps your liquids either hot or cold gets compromised and loses its efficiency. If you're absolutely desperate (a.k.a. you finally found a lost insulated tumbler under your car seat after a long, hot summer month), opt for the top rack and skip the high heat of the drying cycle.

Copper mugs & cookware: Copper is a classic yet stylish pick for your cookware, and copper mugs are perfect for serving up Moscow Mules all year long. Though you may be tempted to throw them in the dishwasher after a big holiday party, make sure to hand-wash any copper items or those of other precious metals to keep shine and luster in tact, as well as to avoid discoloration or tarnishing.

Containers with adhesive labels: This one is more for your dishwasher than you. We've been known to save glass jars and containers for reusable storage purposes, and the first stop is always the sink or dishwasher. However, it's extremely important to make sure the paper label is completely removed beforehand. If it dislodges during the cycle, it can clog the dishwasher drain and food disposal system and lead to damage with a hefty price tag.

Aluminum cookware: The extremely hot water of the dishwasher can stain or dull aluminum cookware. Stainless steel has a better chance in the machine, but you should always check the labels after purchasing. In our experience, better safe than sorry!

Wooden utensils & cutting boards: The hot water and heated dry of the dishwasher can warp or crack wooden kitchen utensils and cutting boards, which renders them less-than-useful. Plus, the heat dries out natural wood cutting boards, making them look sad and faded.

Milk glass: Whether you're picking up retro-chic milk glass bowls from your great aunt or from Anthropologie, be sure to hand-wash them unless you're ready to risk discoloration. The semi-opaque milk glass will turn out looking yellow.

Pressure cooker lids: This one is a big no-no. While your pressure cooker pot might be just fine, the lid poses a safety issue. The dishwasher cycle can warp or damage the rubber seal on the lid, as well as damage the valves and vents that the lid uses when cooking. These things can lead to many problems, including pressure cooker explosions.

Fine china & crystal: This should be a given, but we'd never get past the guilt if we didn't at least give fair warning. Before you line up Mama's heirloom dishes and glasses in the dishwasher, think again. It can cause them to chip, fade, or lose their finish. This is especially important if the patterns have metallic detail.

Nonstick skillets & sheet pans: We know that some nonstick cookware is reportedly "dishwasher safe." We don't distrust that fact, per se, but we also know that the dishwasher can degrade the nonstick coating on your nonstick skillets and sheet pans, rendering them less effective. Read your labels, and proceed with caution.

So always remember, your dishwasher works some magic, to be sure—but not miracles. Keep this list handy, and don't ruin your favorite kitchen tools.