The Science Behind Washing Dishes, or Washing Dishes the Geek Way


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Dishwashing (or washing up, depending on your location), while a calming and meditative time for some, is not everybody’s idea of fun. But fortunately it offers two factors which should appeal to any geeks: science and logic.

Whether you’ve been taught by a kindly relative, discovered it from trial and error, or resorted to a Google search, you likely know that washing dishes effectively requires hot soapy water. But why is this, and why does cold or clear water not do the trick as well?

The key to the soapiness in this situation is that you are not usually tackling dirt (as with laundry) but specifically oils and grease. Most of the active components of dishwashing detergent (also known as washing up liquid) are surfactants, a contraction of “surface active agent”. Put simply, these are made of molecules which have a hydrophilic head, meaning it is attracted to water, and a lipophilic tail, meaning it is attracted to grease and oil.

These molecules then form into tiny balls known as micelles (pictured right) in which the hydrophilic heads form the surface of the ball. As the micelles form, come apart, and then reform, the lipophilic tails grab on to the grease and separate it from the surface of the item being washed. This makes it much easier to then remove the grease from the item with a dish brush.

Why hot water? It’s partly because some of the components of detergent are more soluble at hotter temperatures, and partly because the heat helps melt some of the fats and grease. (Of course, hot water also has other benefits such as being more likely to kill any bacteria and meaning your crockery and cutlery will dry quicker.)

With the science taken care of, the next step is the order in which to do the dishes. While you could just do them in whatever order you can reach them, the true geek way is to find the method which cuts down time and motion, while maximizing the results as you go, and ideally using the minimum amount of water that does the trick. The key is to remember that the water will naturally get dirtier as you clean, which affects its ability to clean items as you go on — but the point at which this becomes a problem depends on exactly what you are cleaning.

Your mileage may vary, but my assessment is that the most efficient method is to begin by scraping off any large remnants of food from all your cutlery and crockery, then filling any particularly greasy pans with hot water to soak. Then, rather than muddle through, start by arranging the things to be washed into piles, arranged in this order of proximity to the sink:

•    glass
•    cutlery
•    cooking utensils (wooden spoons, ladles, etc)
•    crockery
•    other ceramics
•    plastics
•    metals

Then add some detergent to the washing up bowl and a couple of inches of hot water, sloshing the bowl about as you do to create a lather. (Whether you scientifically need the lather appears debatable, but it does create a useful visual guide to how much detergent is left in the water.) If you have particularly delicate glass, you may want to start with warm rather than piping hot water.

For each pile, wash it and add it to an upside down pile besides the sink. When the whole pile is done, turn on the hot tap again and pass each item under the tap to rinse it before placing it in a right-way-up pile on the other side of the sink. Stop the tap when you’re done and then wipe each item (or put them on a drying rack, depending on your preferences.) Then move on to the next step.

Using this method means that you don’t waste any water while rinsing as it’s all collected in the bowl. You’ll note the depth of the water increases quite neatly in line with the items being washed getting bigger. You should also find that the items you wash later are more resistant to becoming streaked by any greasiness that has built up in the water. However, you should still replace the water completely if it either starts to feel tepid or if the bubbles have disappeared completely.

Of course, that’s just my take. If you’ve spotted a flaw in the science, or think you’ve got a more efficient way of doing things, please do let us know in the comments section.

[Illustration courtesy of Flickr user lsgcp]





21 Responses to The Science Behind Washing Dishes, or Washing Dishes the Geek Way

  1. I was taught to wash up by my mum, who back in the day used to run pubs and hotel in post-war England. She knew her washing up! Her rule was “Glass first, it shows the marks, then start from the mouth and work outwards”, i.e. cutlery, crockery, then pots and pans. Funnily enough, exactly the same order science suggests. Makes it real easy to remember if you’re teaching kids to wash up by hand.

  2. I was taught to wash up by my mum, who back in the day used to run pubs and hotel in post-war England. She knew her washing up! Her rule was "Glass first, it shows the marks, then start from the mouth and work outwards", i.e. cutlery, crockery, then pots and pans. Funnily enough, exactly the same order science suggests. Makes it real easy to remember if you're teaching kids to wash up by hand.

  3. Nice article. Are washing machines more or less efficient that a manual wash up like this?

    My instinct tells me that washing machines spend more energy and water than a person washing up because the machine can’t really see the items it’s supposed to wash, and therefore just throws jet after jet of hot water and detergent, in an effort to cover the surface of every item.

    But some people tells me it’s the other way around.
    Perhaps they use less water, but more electricity.

    Any sources I can read about this?

  4. Nice article. Are washing machines more or less efficient that a manual wash up like this?

    My instinct tells me that washing machines spend more energy and water than a person washing up because the machine can't really see the items it's supposed to wash, and therefore just throws jet after jet of hot water and detergent, in an effort to cover the surface of every item.

    But some people tells me it's the other way around.

    Perhaps they use less water, but more electricity.

    Any sources I can read about this?

  5. Where in the world do they call it "washing up?"

    Also, I can't say I've ever NOT had a dishwasher (except when camping) so I'd never heard of the "order of operations" for washing dishes…

  6. Where in the world do they call it “washing up?”

    Also, I can’t say I’ve ever NOT had a dishwasher (except when camping) so I’d never heard of the “order of operations” for washing dishes…

  7. From Wikipedia:

    Comparing the efficiency of automatic dishwashers and hand-washing of dishes is difficult because hand-washing techniques vary drastically by individual. A 2004 peer-reviewed study concluded that the best automatic dishwashers available at the time, when fully loaded use less electricity, water, and detergent than the average European hand-washer. The most efficient hand-washers in that study, however, were far more energy efficient than the dishwashers. In particular, dishwashers that are capable of heating water internally, like cold fill European models, do not lose heat during transport to the faucet as the quantity of water to be loaded is usually very little, on average of 4-5 liters for each section of the wash. The study does not address costs associated with the manufacture and disposal of dishwashers, the cost of possible accelerated wear of dishes from the chemical harshness of dishwasher detergent or the value of labour saved.

  8. From Wikipedia:

    Comparing the efficiency of automatic dishwashers and hand-washing of dishes is difficult because hand-washing techniques vary drastically by individual. A 2004 peer-reviewed study concluded that the best automatic dishwashers available at the time, when fully loaded use less electricity, water, and detergent than the average European hand-washer. The most efficient hand-washers in that study, however, were far more energy efficient than the dishwashers. In particular, dishwashers that are capable of heating water internally, like cold fill European models, do not lose heat during transport to the faucet as the quantity of water to be loaded is usually very little, on average of 4-5 liters for each section of the wash. The study does not address costs associated with the manufacture and disposal of dishwashers, the cost of possible accelerated wear of dishes from the chemical harshness of dishwasher detergent or the value of labour saved.

  9. Our dishwasher is a study in inefficiency, so I’ve taken to doing dishes by hand to not only save water, but to get the dishes clean and sanitized.

    I also do glass, then plates, then silver (which were soaking under the plates) then heavier items. Since I use Dawn, I sometimes put a small squish of it on the greasier plastics, it takes out stains and that icky greasy feel. My cast iron I wash after everything. Yes, I use soap and hot water. I HATE the idea of rancid oil or fat rotting and gathering bacteria. My carbon coat is superb, a scrub with hot hot water and a bit of soap doesn’t harm it at all! I then dry it over an open flame, and then add a bit of oil to recoat it. Non stick as ever!

    I have 2 sinks, so I can put vinegar in my rinse water because it’s so hard. No spots on my glass or silver!

    And men, if you find the water is too hot for your hands, put on some Daisies/rubber gloves and suck it up! I find women have a higher tolerance for hot water. But germs don’t, so get that water as hot as you can stand! (unless the glass is cold or thin, it CAN break!)

  10. Our dishwasher is a study in inefficiency, so I've taken to doing dishes by hand to not only save water, but to get the dishes clean and sanitized.

    I also do glass, then plates, then silver (which were soaking under the plates) then heavier items. Since I use Dawn, I sometimes put a small squish of it on the greasier plastics, it takes out stains and that icky greasy feel. My cast iron I wash after everything. Yes, I use soap and hot water. I HATE the idea of rancid oil or fat rotting and gathering bacteria. My carbon coat is superb, a scrub with hot hot water and a bit of soap doesn't harm it at all! I then dry it over an open flame, and then add a bit of oil to recoat it. Non stick as ever!

    I have 2 sinks, so I can put vinegar in my rinse water because it's so hard. No spots on my glass or silver!

    And men, if you find the water is too hot for your hands, put on some Daisies/rubber gloves and suck it up! I find women have a higher tolerance for hot water. But germs don't, so get that water as hot as you can stand! (unless the glass is cold or thin, it CAN break!)

  11. Are you serious? The most efficient way is to only use one dish and wash it whenever you finish using it.

  12. Are you serious? The most efficient way is to only use one dish and wash it whenever you finish using it.

  13. For the past couple of years I have washed everything up in cold water. In the country where I live it is usual to wash every single item with a sponge and detergent and then to rinse everything individually and well. I tend to give everything a good rinse first to get stuff off the plates. I also do things in order of relative dirtiness which means that glasses come first. You don’t want them getting mixed up with greasy things – it just makes more work. Frying pans get a wipe with kitchen paper first – this saves on using soap and generally all pans can be washed immediately after putting food on the plates and it really takes just seconds. Leaving food to harden on plates etc is what makes washing up difficult. I’ve given dinner parties where I’ve washed all the plates in minutes before serving dessert and noone has noticed. I can do the rest in a couple of minutes after everyone has left – no dishes to face next morning. I’m extremely geeky as far as washing up goes and I refuse to work a different system to anyone else. My poor wife …

  14. For the past couple of years I have washed everything up in cold water. In the country where I live it is usual to wash every single item with a sponge and detergent and then to rinse everything individually and well. I tend to give everything a good rinse first to get stuff off the plates. I also do things in order of relative dirtiness which means that glasses come first. You don't want them getting mixed up with greasy things – it just makes more work. Frying pans get a wipe with kitchen paper first – this saves on using soap and generally all pans can be washed immediately after putting food on the plates and it really takes just seconds. Leaving food to harden on plates etc is what makes washing up difficult. I've given dinner parties where I've washed all the plates in minutes before serving dessert and noone has noticed. I can do the rest in a couple of minutes after everyone has left – no dishes to face next morning. I'm extremely geeky as far as washing up goes and I refuse to work a different system to anyone else. My poor wife …

  15. Sigh, this article gives geek class to ever present dish washing but doing the dishes, over and over again, remains my idea of hell.

  16. Back in the day when it was required for girls to take Home Economics, we had to memorize a poem that started "First the shining crystal, then the silverware…" and I don't remember the rest. Anyone else remember that poem? I googled it and found this page–which basically recommends the same procedure.

    • I was actually looking for the last line of that poem when I came upon this site.
      the way I learned it at PS 45 on Staten Island was
      First the shining crystal
      Then the silver bright
      Delicate cups and saucers
      We will wash alright.
      Then the larger dishes
      Bowls and platters too…
      ??????probably something about pots and pans, no?

      • my mother was trying to remember the poem also. She can add "When we do the dishes we will do them right" This is probably the ending of the poem.