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Dishwasher symbols explained

Dishwasher Safe Dishes

Do you know which items in your home are dishwasher safe?

What does dishwasher safe mean?

Generally speaking, manufacturers will say an item is ‘dishwasher safe’ if they’ve treated it at some stage of the production process to ensure it can withstand both the prolonged high temperatures and the detergents involved in a dishwasher cycle. There are different techniques that manufacturers use to ensure their products are dishwasher safe, with methods varying depending on the material in question.

How manufacturers make items dishwasher safe

As we’ve mentioned already, manufacturers use different techniques to make their items ‘dishwasher safe’. Below we cover some of the main materials you’ll find in your kitchen or home, and how they are treated:

Dishwasher Safe Glass

Most glass is ‘annealed’ which means that when it is made, it is slowly cooled to even out any stresses within its structure. It’s a routine process that almost all glass products go through and helps make ensure any residual internal stresses are relieved. Annealed glass is often called ‘untreated glass’, because there are two other processes that glass can be put through to make it more resilient to drastic temperature changes.

Glass can be put through either a process called ‘tempering’, which is a thermal or chemical process that makes glass tougher and stronger, or a milder form of tempering known as ‘heat-strengthening’. Kitchenware is usually heat-strengthened, and this makes it much more resilient than annealed glass. You may find that some cookware is fully-tempered, making it significantly stronger than annealed glass, and able to withstand microwaving.

Dishwasher Safe Ceramics

Ceramics are made dishwasher safe through a similar process as glass: slow cooling that allows the material to settle with as few imperfections as possible. In short, a glaze is applied to ceramics to protect the surface. The type of glaze used can dramatically affect the strength and durability of a ceramic item. Always check for the dishwasher safe symbol before putting your ceramic items in a dishwasher.

Dishwasher Safe Plastics

Plastic items typically don’t need to be ‘treated’ to make them dishwasher safe because the type of plastic used to make the item often determines whether or not it is dishwasher safe. Plastics with a very low melting point can melt in the high temperatures of a dishwasher. Only place plastics in the dishwasher if they are clearly marked with a dishwasher safe icon and stick to the top rack when you do so. For more information read our article Can I put plastic in the dishwasher?