Dishwashers are incredibly convenient, but not everything belongs inside one. High heat, strong detergents, and powerful water jets can damage delicate materials, shorten the life of cookware, or even create problems inside the machine itself.

The simplest rule is this: if the manufacturer says “hand wash only,” follow that instruction.

Here are eight items that are usually better washed by hand.

1. Sharp  Kitchen Knives and Wooden Utensils

High-pressure water can cause knife blades to knock against other items, which may dull them faster. Heat and detergent can also damage wooden handles, causing them to crack, dry out, or warp.

Wooden spoons, cutting boards, and similar utensils may also lose their finish over time.

Better care

Wash sharp knives and wooden utensils by hand with warm water and mild dish soap. Dry them immediately after washing.

For wooden handles or utensils, occasional treatment with food-safe mineral oil may help preserve the surface.

2. Crystal Glassware and Fine China