This article was originally published on Crafting Your Home. A human contributor also wrote and edited the post.
Dishwashers are convenient, but they are also harsh. High temperatures, powerful water jets, and strong detergents can damage certain materials over time. Some items may survive one cycle, but repeated washing can cause warping, dulling, rusting, or loss of finish.
The following list covers common kitchen and household items that experts recommend washing by hand to preserve their quality and safety.
Cast-Iron Cookware
Cast-iron skillets and pots rely on a layer of baked-on oil called seasoning to create a natural non-stick surface and prevent rust. Dishwasher detergent and prolonged water exposure strip away this seasoning, leaving the iron vulnerable to corrosion.
Once rust forms, you must scrub the pan, re-season it, and maintain it carefully to make it usable again. Most experts advise hand-washing cast iron with warm water and a brush, then drying and oiling it promptly.
Sharp Kitchen Knives
High-quality chef’s knives, paring knives, and other sharp blades can be damaged in the dishwasher. The blades may knock against other utensils, racks, or the dishwasher interior, causing nicks and dulling the edge. Heat and detergent can also affect handles, especially if they are made of wood or certain composites.
Even knives labeled “dishwasher-safe” often last longer when washed by hand. A quick wash with mild soap, immediate drying, and proper storage will keep the edge sharper for longer.
Wooden Cutting Boards and Utensils
Wood absorbs water, swells when wet, and can crack as it dries. The high heat and long wet cycles in a dishwasher accelerate this process, causing boards and utensils to warp, split, or develop rough surfaces.
Cracks and splits can trap food particles and bacteria, making the wood harder to clean and less hygienic. Experts recommend washing wooden items quickly by hand with mild soap, avoiding soaking, and drying them upright.
Non-Stick Cookware Without a Dishwasher-Safe Label
Many non-stick pans have coatings that can degrade under harsh dishwasher conditions. Abrasive detergents and high heat, especially during the drying phase, may wear down the non-stick surface over time.
Even if a pan is labeled “dishwasher-safe,” frequent dishwasher use can shorten its lifespan. Hand-washing with a soft sponge and mild detergent helps preserve the coating.
Aluminum Pots, Pans and Bakeware
Uncoated aluminum can react with dishwasher detergent, leading to discoloration, dulling, or a greyish film on the surface. Over time, this can affect the cookware’s appearance and performance.
Aluminum items with non-stick or anodized coatings may be more resistant, but plain aluminum is best washed by hand with gentle soap.
Fine Crystal and Delicate Glassware
Crystal stemware, decorative glass, and thin glass items can crack, chip, or break due to the high heat and mechanical action inside a dishwasher. The intense temperature changes between washing and drying cycles can also create stress in the glass.
Hand-washing delicate glassware with lukewarm water and a soft cloth reduces the risk of damage and helps preserve clarity and shine.
Dishware with Metallic Trim or Hand-Painted Designs
Plates, cups, and bowls with gold, silver, or other metallic trim can lose their finish in the dishwasher. Harsh detergents and heat can cause the decoration to fade, peel, or become dull.
Hand-painted or hand-decorated items are also at risk of losing their designs. Washing these pieces gently by hand helps maintain their appearance.
Vacuum-Insulated Bottles and Thermoses
Many insulated bottles and travel mugs have sealed vacuum layers and gaskets that dishwasher heat and pressure can compromise. The seals may degrade, reducing the bottle’s ability to keep liquids hot or cold.
Dishwasher detergent can also leave residues inside the bottle or affect the taste of beverages. Manufacturers often recommend hand-washing with warm soapy water and a bottle brush.
Certain Plastics Not Marked Dishwasher-Safe
Plastic containers, lids, and utensils not labeled “dishwasher-safe” can warp, melt, or release chemicals when exposed to high dishwasher temperatures. Even some labeled plastics may become brittle or discolored over time.
Check the manufacturer’s instructions and look for a dishwasher-safe symbol. When in doubt, wash plastic items by hand on the top rack or avoid the dishwasher entirely.
Pressure Cooker Lids and Certain Appliance Parts
Pressure cooker lids, blender bases, food processor motors, and similar appliance parts often contain rubber seals, valves, or electrical components that water and heat can damage.
Dishwasher exposure can warp seals, clog vents, or affect the appliance’s performance and safety. Clean these parts according to the manufacturer’s instructions, usually by hand.
Copper Cookware and Decorative Copper Items
Copper pots, pans, and decorative items can tarnish or discolor in the dishwasher. Harsh detergents may strip protective coatings and accelerate oxidation, leaving the copper dull or spotted.
Hand-washing copper with appropriate cleaners helps maintain its shine and prevents damage.
Knives with Wooden or Bone Handles
Knives with natural material handles are particularly vulnerable in the dishwasher. Heat and moisture can cause the wood or bone to swell, crack, or loosen from the blade.
Over time, this can make the knife uncomfortable or unsafe to use. Hand-washing and immediate drying preserve both the blade and the handle.
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