A loud crash during a dishwasher cycle can be frightening, especially when opening the appliance reveals broken glass scattered across the racks and bottom of the machine.

The source material does not identify a homeowner, appliance model, repair report, or verified incident in which an entire dishwasher “shattered.” A more realistic explanation is that delicate or improperly loaded glassware broke during the cycle.

Dishwashers combine hot water, detergent, strong spray action, and movement from items that may not have been secured properly. Most everyday plates, bowls, and utensils handle those conditions well, but certain materials can crack, warp, discolor, rust, or lose their protective finish.

GE Appliances advises securing dishes so they cannot move during a cycle and placing delicate glassware in the upper rack. Whirlpool similarly recommends hand-washing items such as fine crystal, wooden utensils, certain cookware, and kitchen knives.

Before loading the next cycle, take a closer look at these 10 categories.

1. Fine Crystal and Delicate Glassware

Thin glassware can chip or break when it shifts against another item, is struck by a strong water jet, or experiences thermal stress.

Crystal may also become cloudy or etched after repeated exposure to dishwasher detergent. Some pieces are technically labeled dishwasher-safe, while others should always be washed by hand, so the manufacturer’s care instructions matter.

When the manufacturer permits dishwasher cleaning, place glasses securely in the upper rack. They should not touch one another, and tall stemware must have enough clearance to avoid hitting the top of the dishwasher when the rack moves.

Never reach blindly into a machine containing broken glass. Turn off the appliance, allow everything to cool, wear protective gloves, and remove large fragments carefully before checking the filter and drain area.

2. High-Quality Kitchen Knives

A dishwasher may be convenient, but it is not always kind to a sharp knife.

Heat, moisture, and strong detergent can affect the blade, loosen certain handles, and contribute to corrosion or discoloration. The knife can also strike other utensils during the cycle, damaging both its cutting edge and the surrounding items.

Sharp knives create an additional unloading hazard when their blades are hidden among other utensils. Whirlpool recommends hand-washing kitchen knives, and its care guidance notes that adhesives used in some handles may loosen in a dishwasher.

Wash a quality knife with warm water and mild dish soap, dry it promptly, and store it where the blade will not be damaged.

3. Wooden Spoons, Utensils, and Cutting Boards

Wood repeatedly exposed to water and heat may swell, warp, split, or develop a rough surface.

Dishwasher detergent can also strip oils from the material, shortening the life of wooden spoons, rolling pins, salad servers, and knife blocks. Whirlpool lists wood among the materials generally better suited to hand-washing.

Not every wooden cutting board is identical. The USDA notes that some solid wood boards may tolerate dishwasher cleaning, while laminated boards can crack and split. The safest approach is to follow the board manufacturer’s instructions rather than assuming every wooden item should be treated the same way.

After hand-washing wood, dry it thoroughly instead of leaving it submerged in a sink.

4. Traditional Cast-Iron Cookware

An ordinary seasoned cast-iron skillet should not go into the dishwasher.

The long, wet cycle and detergent can remove the seasoning that protects the cooking surface. Remaining moisture can then promote rust. Lodge explicitly advises washing its traditional cast-iron cookware by hand.

Clean cast iron according to its manufacturer’s directions, dry it immediately, and apply a light coating of oil when appropriate.

Enameled cast iron is different. Some enameled products are technically dishwasher-safe, although manufacturers may still recommend hand-washing to preserve the finish.

5. Some Nonstick Pots, Pans, and Baking Sheets

“Nonstick” does not automatically mean “hand-wash only”—but it also does not guarantee that every coated item belongs in a dishwasher.

Some current nonstick cookware lines are dishwasher-safe. Others carry hand-wash-only instructions, and even dishwasher-safe coatings may retain their appearance and performance longer with gentler cleaning. OXO, for example, describes some ceramic nonstick cookware as dishwasher-safe while recommending hand-washing to extend its life; another of its nonstick products is explicitly labeled hand-wash only.

Check the product’s care label or manual. Avoid assuming that instructions for one brand or cookware line apply to another.

Replace a pan when its coating is severely peeling, blistering, or separating rather than attempting to scrub the damage away.

6. Insulated Travel Mugs and Bottles Without Dishwasher Approval

The advice that all insulated drinkware must be hand-washed is outdated and overly broad.

Many modern insulated products are dishwasher-safe, sometimes only on the upper rack. Stanley advises checking the bottom of the product or its care instructions, while Thermos states that most of its products are top-rack dishwasher-safe but still recommends hand-washing when preserving the finish is a priority.

Other models may require the stainless-steel body to be washed by hand, even when the lid and straw can enter the dishwasher. A high-heat drying cycle may also be discouraged for some products.

Disassemble removable seals and lids according to the manufacturer’s instructions so trapped residue does not remain hidden inside.

7. Aluminum Cookware With a Sensitive Finish

Some aluminum products can be cleaned in a dishwasher, but detergent and hot water may alter the finish.

Anodized aluminum may become dull, stained, pitted, or discolored. Disposable aluminum should generally be kept out of the appliance. Whirlpool advises checking manufacturer recommendations because the effect varies by product.

The appearance may change even when the pan remains usable. Hand-washing is usually the safer choice for valuable or carefully finished aluminum cookware.

8. Copper Pots, Pans, and Utensils

Copper is prized for its appearance and responsiveness during cooking, but dishwasher detergent can leave its polished surface dull or discolored.

Items with copper exteriors, decorative finishes, or mixed-metal construction should be cleaned according to their manufacturer’s care instructions. Hand-washing with a nonabrasive sponge is often the cautious choice.

Do not use harsh polish on cookware interiors unless the product manufacturer specifically approves it. Decorative copper and functional copper cookware may have different coatings and care requirements.

9. Antique, Hand-Painted, or Gold-Trimmed Dishes

A plate may survive one dishwasher cycle and still experience gradual damage after repeated washing.

Heat and detergent can fade hand-painted decorations, soften overglaze patterns, and discolor gold trim. Whirlpool’s care guidance specifically warns that antique, hand-painted, and overglaze designs may fade, while gold leaf can discolor.

Older dishes may also contain small cracks, repairs, or adhesives that are not obvious until the item is exposed to heat and water.

Sentimental china, heirloom dishes, and pieces with unknown care requirements are best washed individually by hand over a padded or towel-lined sink.

10. Plastic That Is Not Clearly Marked Dishwasher-Safe

Plastic products vary considerably in their ability to tolerate dishwasher temperatures.

A thin takeout container, disposable lid, or unidentified plastic item may soften, warp, or fall through the rack. A distorted item can also interfere with moving components if it reaches the heating area or spray mechanism.

Only place plastic in the dishwasher when the product is labeled for that use. When the instructions specify the upper rack, keep it there, farther from the machine’s hottest areas.

Whirlpool recommends consulting the manufacturer when there is doubt about whether a material or item is safe for dishwasher cleaning.

How Improper Loading Can Break Otherwise Safe Dishes

Even dishwasher-safe glass can break when loaded incorrectly.

Place items firmly between or against the rack supports so they cannot collide. Do not position glasses over the tines in a way that allows them to wobble. GE recommends loading glassware on the upper rack and leaving enough clearance around delicate items.

Avoid overcrowding. A tightly packed rack may prevent proper cleaning while increasing contact between fragile pieces.

Tall utensils, cutting boards, and pan handles must not block the spray arms. Bosch recommends leaving adequate space between dishes and checking that tall items do not prevent the arms from rotating.

Before starting the machine, rotate the spray arms gently by hand to confirm that nothing obstructs them.

Maintain the Dishwasher, Too

Regular maintenance cannot make an unsuitable item dishwasher-safe, but it can keep the appliance operating more reliably.

Inspect and clean the filter according to the owner’s manual. Check spray arms for food particles or mineral deposits, wipe the door seals, and use only cleaning products approved for the machine. Bosch provides separate maintenance guidance for filters, spray arms, pumps, and interior cleaning.

Stop using the dishwasher and contact a qualified service professional when it leaks, produces an electrical smell, repeatedly trips a circuit breaker, displays an unresolved error, or makes abnormal mechanical noises.

The Bottom Line

Dishwashers do not normally “explode” because one unsuitable cup was placed inside. However, fragile glassware can shatter, plastic can deform, wood can split, cast iron can rust, and decorative finishes can be permanently damaged.

The most reliable rule is simple: check the manufacturer’s instructions before loading an unfamiliar or valuable item.

Secure glassware, avoid overcrowding, keep spray arms clear, and wash delicate or sentimental pieces by hand.

A few additional minutes at the sink can prevent broken dishes, damaged cookware, an expensive appliance repair, and the unpleasant surprise of opening the dishwasher to find shattered glass throughout the machine.