Question inspired by this thread, “Do dishwashers actually work?”, although I’ve wondered about it sporadically over the years.
Note, I’ve never actually used a dishwasher myself. I just eat straight off the floor, usually.
Okay, so you pile all your dirty dishes, of various shapes and sizes, and bowls and pots too? And these are mostly standing up on edge side by side, with all the silverware in one bucket on the side, and bowls and pots wherever they will fit?
How does the washer get to all the surfaces of all those pieces? Does it just get so hot as to vaporize all uncleanliness? (Kind of like self-cleaning ovens supposedly do? I’ve never tried that either.) Does it squirt sprays of water with such high pressure that the water bounces around enough to get into every cranny? Or does some of the water quantum-tunnel through every item to get at the next item over? Does the washer actually fill with water like a laundry washing machine, and then slosh it all around vigorously?
Even if one used a washer regularly, how would one know how it does what it does? I don’t think I’ve ever seen one with a glass or plexiglass door that you could watch while in action.
(ETA: If there have already been threads galore on this question, as is probably the case since EVERY imaginable topic already has threads galore, I’d be happy enough just to see links. I didn’t search myself because I decided spontaneously to ask just now. We folks who do things like eating off the floor are impulsive like that.)
There is a spinning arm (two in a big machine) which shoots jets of very hot water at various angles. That’s generally sufficient to reach the surfaces of everything unless you do something dumb like put the glasses in right-side-up.
Also, the dish detergent helps the hot water loosen the dirty bits of the dishes. That gets the dishes physically clean. 180+˚F water then sanitizes durring the rinse cycle to get the dishes biologically clean.
I assume it just sprays so vigorously that it gets in every cranny: there is no other explanation though it always amazes me how clean everything gets even when you are (relatively) ambitious in terms of cramming the dishwasher every which way.
NB: dishwashers are usually more sanitary than handwashing. Supposedly, your kitchen sink is one of the most unsanitary places in the house (yes, that includes your herpes-riddled toilet seat). Also, they are usually less wasteful of water (and time!) than handwashing. Unless you wash super spartan. The water sprays in many directions, but generally upward and out from the center. For efficient cleaning, you put the eating side of bowls, plates, etc., facing downwards and towards the middle. Silverware goes in the basket, and cleaning efficiency depends on how tightly you pack them.
For that other thread (this one is shorter): if you have to rinse more than 1/10 dishes first, you’re doing it wrong. Usually the tricky ones have some baked-on food, or greasy stuff like peanut butter (dogs make a good prewasher for that).
I cannot speak for every dishwasher everywhere, but domestic dishwashers in the UK do not get anywhere near so hot, and rinses are either cold or use the hot water from the home supply, they do not heat it themselves.
[“… Dishwashers heat up the water in a very efficient way by using a continuous-flow heater which results in less heat loss than heating water in a tank and transporting it to the sink…”
A quick google brings up heaps more cites. Now admittedly 70C isn’t 180F, but it’s not far off and it is substantially more than what domestic hot water tap would put out. Looking at your UK dishwashers they don’t seem any different to what is sold anywhere else in the first world.
I was specifically talking about the rinses, not the wash parts off the cycle, as the previous poster had suggested that there was a near boiling rinse to “sanitise”. I admit I’m surprised by the claim that domestic washers get up to 70C - I thought 55-60 was more normal.
Anyway, yes, they heat the wash water that goes around with the detergent, and the extra heat helps to clean the food off the dishes. They do not heat the rinse water.
All the dishwashers I have had do, or at least have that option. Open the door during the rinse cycle and you are inundated with a steam cloud that fogs up your glasses.
[Most consumer dishwashers use a 75°C thermostat in the sanitizing process. During the final rinse cycle, the heating element and wash pump are turned on, and the cycle timer (electronic or electromechanical) is stopped until the thermostat is tripped. At this point, the cycle timer resumes and will generally trigger a drain cycle within a few timer increments.
Most consumer dishwashers use 75°C rather than 83°C for reasons of burn risk, energy consumption, total cycle time, and possible damage to plastic items placed inside the dishwasher.](Dishwasher - Wikipedia)
Actually you have it backwards. Washing is often carried out at lower temperatures because enzyme cleaners operate best then. Rinsing is carried out very hot, to sterilise and also to heat up the dishes so they dry well, the next step.
One other note. The bottom of the dishwasher is bowl like, and has a float to ensure it does not over fill. Thus, you can open the door mid cycle without water pouring everywhere.
The detergent is also very important. It is much more aggressive than handwashing detergent, so it can cut through the mess with just sprays of water.
Our dishwasher has three sources of water spray - there’s one on the top, one in the middle, and one on the bottom. The one in the middle spins, so water gets pretty much everywhere.
Mine says 155 F (68 C) for the NSF-certified sanitizing cycle (Maytag Jet Clean). From what I can figure out, it’s essentially a pasteurization cycle; if the temp and flow is at a certain temp for a certain amount of time, it’s considered sanitized. Lower temp = longer time and vice versa, within certain bounds.
In addition to the already mentioned spray arms and sanitizing cycle, mine has a soil sensor that somehow regulates the cycle length based on how dirty the dishes are, a “steam” feature that I suppose floods the dishwasher with high temp steam or water vapor for a while to soften hardened gunk, and the option to use hotter water than the standard.
