10 things you should never put in a dishwasher

Things you shouldn't put in a dishwasher
(Image credit: Getty Images)

Dishwashers take the hard work out of doing the dishes, and while it’s tempting to throw everything in, there are some things that you shouldn’t put in a dishwasher.  The chemicals in dishwasher detergents, along with the action of the water jets, can cause damage to certain items. And it’s not just super delicate or expensive things that you need to avoid cleaning in the dishwasher, plenty of seemingly sturdy and robust kitchen items can’t handle being cleaned in the dishwasher either.

If you’ve invested in one of the best dishwashers, you might be keen to use it as much as possible, so check out these surprising things you can sanitize in your dishwasher. But don’t get too carried away. To help you avoid damaging and potentially having to replace expensive items of kitchenware, we’ve pulled together a list of the top 10 items that you shouldn’t put in a dishwasher.

Things you shouldn’t put in a dishwasher

1. Wooden cutting boards and spoons

Never put anything made of wood into your dishwasher. The high temperatures and prolonged exposure to humidity in the dishwasher can cause wood to swell, which can cause it to warp and crack. The harsh dishwasher detergents will also strip protective oils out of wooden cutting boards. Also, be aware of wooden handles on metal utensils or pans, as the dishwasher could also damage them.

2. Crystal

Expensive lead crystal glasses should always be washed by hand. Even if your dishwasher has a delicate wash program for glasses, it’s best to avoid using this for crystal. The action of the dishwasher causes items to move around slightly during the wash program, and when combined with abrasive detergents, over time, the glass will become cloudy and pitted, and there’s nothing you can do to revive it. So, even if they come out of the dishwasher in one piece, your crystal glasses may not look crystal clear if you insist on cleaning them in the dishwasher.

10 things you shouldn’t put in a dishwasher

(Image credit: Getty Images)

3. Pressure cooker lids

Although some electric pressure cookers, like the best Instant Pots, have dishwasher-safe lids, the general rule is not to wash pressure cooker lids in the dishwasher. To ensure your pressure cooker keeps performing at its best, wash the lid by hand. Dishwashers circulate small pieces of dirty food during the cycle, and if any of these get lodged in the valves or vents without you realizing, it could cause a fault in the pressure cooker, which could spell disaster if you’re not able to vent it when you need to.

4. Sharp kitchen knives

It’s hard enough to keep your knives sharp at the best of times, but washing them in the dishwasher doesn’t help and can cause them to blunt even more. This happens when the movement inside the dishwasher causes the blades to rub on dishwasher racks or on other things in the dishwasher. Very sharp blades can also damage the coating on dishwasher racks, allowing water to get in and causing them to rust, so they’re not good for your dishwasher either.

5. Cast iron

To get the most out of cast iron cookware it’s best to let a layer of oil build up on the cooking surface over time, this is known as seasoning. Dishwashers will wash away the seasoning and not only cause the cast iron to rust but also destroy any non-stick properties that have built up. Enameled cast iron won’t rust, but cleaning it in the dishwasher can cause the enamel coating to dull.

6. Hand-painted glass and ceramics

If you’re lucky enough to have been gifted a lovingly painted ceramic or glass creation, or if you’ve bought a hand-painted item from a local craftsperson, it’s best to keep it out of the dishwasher. Hand-painted items often don’t have dishwasher-safe glazes, and you risk washing the artwork off completely, so it’s really not worth the risk.

7. Insulated travel mugs and bottles

Reusable travel cups and water bottles that are insulated to keep drinks hot or cold usually have double-wall construction that helps keep drinks at the perfect temperature. Many of these have a vacuum seal, which can be damaged by washing in the dishwasher. So, to keep your favorite travel mug or bottle in tip-top condition, wash it by hand after every use.

8. Vintage or metallic trimmed china

The strong water jets and movement inside a dishwasher can, at times, damage even sturdy crockery, so it’s best to keep delicate, fine vintage china out of the dishwasher, and these items should be carefully hand-washed to avoid damage. If your china has any gold or metallic trims or detail, keep it away from the dishwasher, as these decorations can easily be damaged.

9. Non-stick pans and baking sheets

We know it’s not what you want to hear, pots, pans and baking sheets are no fun to clean, but if you want to preserve the non-stick coatings for as long as possible, it’s best to wash them by hand. Often, cleaning instructions will say the item is dishwasher safe, but hand-washing is recommended, which is the manufacturer's way of telling you it won’t last as long if you wash it in the dishwasher. Non-stick coatings can break down faster if regularly washed in the dishwasher. This is caused by abrasive detergents and knocking against other items during the wash cycle.

10. Very greasy cookware

Your dishwasher uses high temperatures and strong detergents, so it can definitely remove the grease from everything you put in it. But, the problem comes when you put very greasy things in the dishwasher regularly. The grease can end up solidifying in the pipes, and if this builds up over time, it will cause a blockage. The best thing to do is scrape solidified grease into the trash and mop up excess oils with paper towels before putting the item in your dishwasher.

Helen McCue

Helen is a freelance writer who specializes in kitchen appliances and has written for some of the biggest home-related titles around. Helen likes to keep busy and is always thinking about her next DIY project or digging up the garden.