Ever look at a dirty dish and wonder, “Can I put this in the dishwasher?” Sometimes it can be tricky to know whether or not your beloved insulated water bottle or plastic food containers can handle the heat of your dishwasher.
Luckily, there are some manufacturers that actually utilize symbols on the backs of their products to denote whether or not they are “dishwasher safe.” Much like the garment care symbols, dishwasher safe symbols help guide consumers as they clean their kitchenware.
Unfortunately there is not a singular, universal dishwasher safe symbol! This guide will decode the dishwasher safe symbols you are most likely to see.
What makes an item dishwasher safe?
Dishwasher safe items have undergone a treatment at some phase in production to make them dishwasher safe. From tempered glass to slow cooled, glazed ceramics, dishwasher safe products are built to withstand exposure to dishwasher detergents and heat for extended periods of time.
Dishwasher Safe Glass
Glassware that has been manufactured to minimize weak points in the structure are going to be dishwasher safe. Three common types of dishwasher-safe glass you’ll find in a kitchen include the following:
Annealed or “untreated glass” is a treatment where glass is cooled slowly to minimize weak points in the final piece. With that said, annealed glass tends to break in longer, sharper (more dangerous) shards, so it is most often used for products where strength or safety are less of a concern. (1)
Tempered glass goes through a thermal or chemical process that makes it resistant to breaking. This process makes tempered glass about 4 times stronger than regular (annealed) glass. (2)
Heat Strengthened Glass
Heat strengthening is a milder form of tempering glass. The resulting glass has a higher heat resistance than annealed glass, but breaks into fragments that are larger than you would see with tempered glass. (3)
Dishwasher Safe Ceramics
Dishwasher safe ceramics undergo a slow cooling process that allows ceramics to settle with minimal imperfections. Most ceramics are then covered with a glaze to protect the surface.
Most commercially produced ceramics will be marked underneath with a dishwasher safe symbol. If you’re unsure, washing ceramics in warm soapy water is the safest cleaning method.
Dishwasher Safe Plastic
Thinner, lower quality plastics that have a low temperature melting point are not good candidates for dishwasher cleaning. Not only that, the exposure to the heat of a dishwasher can cause harmful chemicals like phthalates and BPA to leach from plastic products that contain them. (4)
The best way to determine if your plastic food containers and cookware are safe to clean in the dishwasher is to check if yours are clearly marked with dishwasher safe labels.
What do Dishwasher Safe Symbols look like?
Most dishwasher safe symbols are images of dishes with diagonal lines coming down from above. The diagonal lines represent water or water droplets washing the dishes.
Occasionally these symbols will include additional information like heat temperature limitations or whether or not the dish is considered food safe (wine glass and plate symbol).
Dishwasher Safe Symbol Examples
Other Important Symbols
Food safe products aren’t always dishwasher safe and vice versa! Food safe symbols usually include a wine glass and a plate or wine glass and fork. Some even include the words “Food Safe.”
Some food safe symbols can also communicate that the product is dishwasher safe. One example below shows diagonal lines (i.e. water droplets) over the food safe glass and dish. This is meant to communicate that the product is food safe AND dishwasher safe.
Microwave safe products usually have a wavy line symbol. Sometimes these wavy lines can be located above a baking dish, within a microwave, or above the word “Micro.”
Maximum and Minimum Temperature
Freezer safe products will most often have a snowflake symbol. Occasionally they will also include the minimum temperature that product can handle.
In other cases, the product will include a minimum and maximum temperature range for the product or just a maximum temperature.
Freezer safe items are denoted with a snowflake symbol. Sometimes this symbol will also be accompanied by a minimum temperature.
Recyclable symbols appear on most packaged products, but they also appear on some manufactured kitchenware items. Recyclable symbols are usually a triangle of arrows.
Some symbols will also include a number (1-7) in the middle. Those numbers represent the type of plastic the product is manufactured from. (5) They work as a code that helps consumers properly recycle their plastics based on their municipality’s recycling process.
What not to load in the dishwasher
Below is a list of products that should never be cleaned in a dishwasher and the damage that could happen if they accidentally are.
- Wood: warp or crack
- Sharp knives: dull
- Crystal, most china, milk glass: can crack
- Hand painted dishware: will wear off
- Cast Iron: rust
- Non-stick pans: coating can chip off
- Baking mats (e.g. silpats): detergent wears them down
- Metals like aluminum, copper, brass, bronze: oxidize
- Any cookware with electrical components (e.g. electric kettle): dangerous
- Cheese graters, sieves, garlic press: must completely remove food remnants first if you wish to wash in a dishwasher (but might as well wash by hand at that point)
- Here’s how to properly load a dishwasher
- How to clean a dishwasher
- List of the best non-toxic dishwasher detergents to try
- One Day Glass: Annealed vs. Tempered Glass
- Scientific American: How is Tempered Glass Made?
- Guardian Glass: Heat Strengthened Glass
- Consumer Reports: Things You Should Never Put in a Dishwasher
- Recyclops: What Do Recycling Symbols Mean?