I always used to say handwashing dishes was good enough for my mother, it will be good enough for me, but according to science, a dishwasher cleans better than hand-washing. Even those dishes that don’t come completely clean will have less bacteria on them than most hand-washed dishes. However, dishwashers are not completely free of bacteria, and studies have found that all dishwashers contain some microorganisms, most are found around rubber seals, but most aren’t considered the least bit harmful to humans.

Hand or machine?

The first decision that might sway you is the bacteria issue, but unless you are absolutely fastidious, washing dishes by hand means most bacteria are living on the sponge or towel you are using. Another thought should be given to the fact that your expensive pots and pans shouldn’t be dishwashed anyway, so you have to wash them by hand. Yep, harm will befall your pots and pans if you put them in the dishwasher. The same goes for aluminium tools like some baking sheets, with food mixer parts (like the dough hook or beater blades) possibly turning black as their surface oxidizes – it can be scrubbed off but it's unsightly and can come off in your food. If you have a bowl of hot soapy water for the pans, why not do the dishes in it too?

And there are more things that should apparently be washed by hand: chef’s knives, any bladed tools, wooden utensils, thin plastic tools and delicate or crystal glassware. Not even your trusty potato peeler, depending on what it’s made of. You have to remember that the dishwasher works by spritzing hot water and strong soap over the dishes across a few hours to soften and loosen food particles. It’s a relatively slow process as everything stays wet and soapy for a very long time, which is terrible for wood tools, cutting boards and knife handles.

Things that can be put in the dishwasher

The list includes everyday china and ceramic dishware, hard plastic, stainless steel items, drinking glasses and sturdy wine glasses, glass and stoneware baking dishes and even silicone and metal utensils. The jug part of your blender and other plastic work bowls, such as those on your food processor are technically OK in the dishwasher, but they may become cloudy looking over time because their surface will become etched by the harsh chemicals and abrasions.

Water usage

You may feel more righteous doing the dishes by hand, but it's actually more wasteful; you can use up to 102 gallons of water a day washing by hand. Depending on the make and model of the dishwasher, as little as 11 litres is used with an energy-efficient dishwasher, and on average, a full machine uses 22 – 49 litres each time.

Is it OK to run the dishwasher half full?

No, half-filling your machine will take just as much water and electricity as filling a complete load, so try to build up a full set of dishes before switching it on.

Are salt and rinse-aid necessary?

Generally speaking, yes. For hard water, salt helps the cleaning process and will help prevent damage from limescale build-up. For soft to moderately hard water all-in-one tabs are typically enough, and soft water doesn’t need salt at all. As for rinse-aid, this not only speeds drying and reduces spotting, but also prevents debris in the wash water from clinging to dishes.

Who invented this wonderful device?

The first to be granted a patent in 1850 was by American Joel Houghton. It was a wooden box that used a hand-cranked wheel to splash water on dirty dishes. But the person we have to thank for the modern-day dishwasher is American socialite Josephine Cochran. She had no formal engineering education, but found mechanics who did, and being fed up with her servants chipping plates while washing up, designed the first machine to use water pressure to clean dishes, making it more efficient. Despite dishwashers being popular with the hospitality industry, it only took off for the American home after the 1950s, but apparently up to 1994, only 18% of UK households had one!


Marilyn writes regularly for The Portugal News, and has lived in the Algarve for some years. A dog-lover, she has lived in Ireland, UK, Bermuda and the Isle of Man. 

Marilyn Sheridan