Dishwasher symbols explained

Do you know which items in your home are dishwasher safe? Learn what the dishwasher safe symbol looks like so stacking it is no longer a guessing game.

Dishwasher symbols explained


The dishwasher safe symbol is one of the trickiest food safety symbols to interpret, and for good reason: there’s no officially approved symbol that signifies an item is dishwasher safe!

What’s more, the phrase “dishwasher safe” isn’t a standard claim either. Each company producing kitchenware or tableware has their own process and standards for determining what can be called dishwasher safe, based on their own methods and materials.

Typically, there are two types of dishwasher safe icons:

  • Dishwasher safe, top rack only
  • Dishwasher safe

If an item is marked ‘top rack only’, it means it’s only safe to be washed on the top rack of the dishwasher. The heating element in dishwashers is typically on the bottom of the machine, which means the top rack is comparatively cooler than the bottom. If you put an item marked ‘top rack only’ in the bottom rack, you may find it has discoloured, warped or become damaged by the end of the cycle!

For both types of dishwasher safe items, typically the dishwasher safe symbol looks like a square box with some plates or glasses (or both) inside it. You’ll also see either water droplets or diagonal lines that are meant to signify water. For items that are only ‘top rack only’, the droplets or diagonal lines will only hit the top of the plates or glasses. If the symbol just shows droplets or lines that cross the entirety of the square box, it’s probably safe to wash the item on either the top or bottom rack.

The image may also include a temperature to clarify the safest top temperature you can wash the item in. Sometimes wording will accompany the symbol, which helps eliminate some of this symbol-deciphering guesswork!


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. 


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 for that dishwasher (unofficial) seal of approval:


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 twice as resilient as annealed glass. You may find that some cookware is fully-tempered, making it four to five times stronger than annealed glass, and able to withstand microwaving.


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.


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.

Does it matter what detergent I use?

Your detergent needs to complement the cleansing action of your dishwasher. Automatic dishwashing detergent is specially formulated to disperse food residue and greasy soiling, hold it in suspension, and remove it in the final rinse. It does all this while producing little or no suds.

For best results use the detergent recommended by the manufacturer of your machine.

However, in very hard water areas we also recommend the use of separate Salt and Rinse aid to protect your machine and achieve the best result.

Do I need to pre-rinse my dishes before loading them into the dishwasher?

No need to! Pre-rinsing is a thing of the past. And although many British households do it, it’s time consuming and wasteful of precious resources.   

Modern detergents such as Finish Quantum Ultimate contain both bleach and enzymes and are recommended by dishwasher manufacturers for use without pre-rinsing.

Bleach fights tough stains like tea and coffee, and enzymes breakdown proteins and starches. All you have to do is scrape the larger pieces into the rubbish bin and load your dishwasher.

How do dishwasher tablets work?

Dishwasher tablets contain surfactants, which affect the liquid they are added to, making it more efficient at picking up and washing away debris. They also include enzymes (to break down starchy foods and protein), builders (to tackle hard water) and safe bleaches.

Once you’ve put your dishwasher tablet into the detergent dispenser compartment, your machine will release the contents at the optimal time allowing the tab to disintegrate into the water, release all ingredients and clean your dishes!

How should I store my dishwashing detergent?

Your dishwashing detergent should be stored in a dry environment. If you are using powder, be careful to close the spout after each use to help keep the product dry (and to avoid spills!). Like all cleaning products, store your detergent out of the reach of children.

Do I need to add salt and rinse aid?

Rinse aid is required to:

  • Ensure spot-free, shiny dishes
  • Assist the drying function

Salt is required to:

  • Protect your machine from limescale
  • Soften the water for better cleaning

With multi-benefit tablets such as Finish Quantum Ultimate and Finish All in One, rinse aid and salt functions are included. However, in very hard water areas we also recommend the use of separate Salt and Rinse aid products to protect your machine and achieve the best result.

How do I use dishwasher tablets?

Dishwasher tablets are very simple to use. If needed, remove any protective packaging, pop the tablet into your detergent dispensing compartment, close the compartment, turn on your washing machine and let technology and Finish handle the rest!

For detailed information on how to use Finish Tablets, read on below.

  1. With dry hands, remove the tablet from the container and place it in the detergent dispenser. Ensure both the dispenser and the tablet is dry to prevent it from dissolving prematurely.
  2. Close the tablets packaging lid tightly. Store away from heat and moisture to protect the remaining tablets.
  3. Our tablets are wrapper-free (with the exception of Finish Classic) and are designed to release their contents when they come into contact with water. Do not pierce or attempt to unwrap the tablets.
  4. Clip the detergent dispenser shut and close your dishwasher.
  5. Make sure all items are dishwasher safe and separate silver from stainless steel.
  6. Wash metal items according to manufacturer’s instructions.
  7. Run dishwasher. The optimal water temperature is 51° – 60°C.

For optimal results, it is recommended to also use Finish Rinse Aid for shinier and drier dishes (vs detergent alone).

Can you put dishwasher tablets in the bottom of the dishwasher?

Detergent tablets should always be placed in the detergent dispenser compartment.

If you’re placing the tablet at the bottom of the dishwasher it’s likely that it will dissolve too quickly, releasing the detergent during the prewash and leaving no detergent for the main wash cycle. This will reduce the efficiency of your wash.

Do I take the plastic off Finish dishwasher tablets?

Whether you need to remove the plastic from your dishwasher tablet depends on the product you have bought. As a good rule of thumb, if the tablet comes individually wrapped then yes, you should remove the plastic wrap before using. If, however, the tablet is encased in a skin of thin, transparent plastic, this should not be removed and will dissolve itself safely during the washing process.

Where do I put the dishwasher tablet?

Dishwasher tablets should only go in the dishwasher detergent compartment of your dishwasher, not loose in the dishwasher itself.

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