A dishwasher doesn’t know that something is special.

It treats an antique plate the same way it treats an ordinary dinner plate.

That’s the problem.

Hand-painted designs, over-the-glaze decorations and older finishes can gradually fade or become damaged.

If you don’t know how an antique piece was made, assume it needs gentler care.

16. Certain aluminum cookware

Aluminum deserves a little nuance.

Some aluminum cookware can go through a dishwasher, while other types can discolor, pit or lose their finish.

Anodized aluminum in particular can react differently.

Whirlpool notes that high water temperatures and detergents can affect the finish of certain aluminum cookware.

So don’t automatically classify every aluminum pan as dishwasher-safe.

Check the cookware manufacturer’s instructions.

17. Items with labels or glued-on parts

Here’s a less obvious problem.

Certain bottles and containers may have labels attached with adhesive.

During a dishwasher cycle, labels can loosen.

Whirlpool notes that loose labels or adhesive can potentially clog spray arms or the dishwasher pump.

So even when the bottle itself might survive the heat, the label can create a completely different problem.

18. Anything that doesn’t say it’s dishwasher-safe

This may be the most useful rule of all.

You don’t need to memorize a list of 18 objects every time you load the machine.

When you’re unsure, look for the dishwasher-safe symbol or check the manufacturer’s instructions.

Modern dishwashers can safely handle many everyday materials, including plenty of glass, ceramic and appropriately labeled plastics. But heat, water pressure and detergent can damage materials that weren’t designed for those conditions.

When in doubt:

Hand wash it.

A minute of extra work is usually cheaper than replacing something you liked.

One more dishwasher mistake people make

There’s another habit worth changing.

Many people completely rinse their dishes under the faucet before putting them into the dishwasher.

That usually isn’t necessary.

Modern dishwasher detergents are designed to work with food particles, and Whirlpool recommends scraping off large pieces rather than thoroughly pre-rinsing every dish.

So you don’t need to wash the dishes before putting them into the machine that’s supposed to wash them.

Remove large food scraps.

Load correctly.

Use the appropriate cycle.

Let the dishwasher do its job.

Don’t block the spray arms

Even dishwasher-safe items can cause problems if they’re loaded incorrectly.

Large plates, cutting boards or cookware can block the spray arms and prevent water from reaching other dishes.

Whirlpool recommends making sure the spray arms can rotate freely and aren’t blocked by the way you’ve loaded the machine.

This is one of those small things that can make a dishwasher seem like it’s “not cleaning properly” when the real problem is simply how everything was arranged.

The easiest rule to remember

Instead of memorizing a giant list, remember four questions:

Is it made of wood?

Is it delicate or valuable?

Does it have a special coating or finish?

Does the manufacturer say it’s dishwasher-safe?

If the answer raises doubts, hand washing is usually the safer option.

And remember that dishwasher-safe doesn’t always mean “put it anywhere.”

Plastic that is approved for the dishwasher may still belong on the upper rack, depending on the manufacturer’s instructions.

The bottom line

The dishwasher is one of the most useful appliances in a modern kitchen.

But it’s not a universal washing machine for everything you own.

Wood, knives, cast iron, certain nonstick cookware, delicate glassware, fine china, insulated containers and special metals can all require extra care.

Before you toss something into the next load, take two seconds to check the manufacturer’s instructions.

That tiny habit could save you from replacing something you never meant to damage.