I'm curious why every front-loaded washing machine I've seen so far comes with a window, while other household machines, like dishwashers, don't.
From a design or UI/UX perspective, why would one want a user to be able to see their clothes while they're getting cleaned? For me, there is nothing I have to control during the process that a window would be helpful for.
In a washing machine the objects that are being washed move around. It's a dynamic process, that is unpredictable and always unique. Watching the movement is fun, it indeed gives a sense of control to the user, even if it is not actually required. Quite a few people even find it relaxing to watch the washing machine. The window also prevents users from trying to open the door when the machine is filled with water.
In addition, it might be useful to some people to actually see what is being washed. If I come home, and see that the washing machine is packed with white fabric, I know I can wear my favorite white shirt soon.
In a dishwasher the items don't move. Making a window in the dishwasher would not expose anything interesting to watch at all. Given the working principle of a dishwasher (same water being reused as much as possible), watching his internal process might actually give you a bad appetite and convince you from hand-washing the dishes. A dish washer also does not fill the whole machine with water. It actually uses very little water. Opening the door while this machine is filled with water would not result in water pouring out of the machine.
Another argument not to have a windows in the dish washer: a benefit of having a dish washer is that you can just put any dirty dish, cup or whatever straight into the machine, thus making the kitchen look more tidy. If you would have a window in the dishwasher you would be looking at dirty dishes again for 90% of the time.
On the other hand, dish washers with a window DO exist.
Electrolux brought this machine to the market after "market research", but it appears to have been removed from their current product range.
In the event of a stopped dishwasher (due to electrical fault or buggy software or something) the water in the device streams out of ordinary drains inside, and the water sprayers stop adding more water. If you were to open it after it had shorted out, you aren't going to get soaked.
That's not true of a front-load washing machine. If one of these is forcibly stopped at certain points in its cycle, then it remains full of damp clothes resting in soapy water.
Opening one of these without knowing what's inside would lead to a rather unpleasant surprise.
The window helps you see what's going on inside in the one case when you do need to interact with it mid-cycle: when it's broken.
Just looked up the answer, and quite a few places seem to have the same thought.
In front load washing machines, the window is given to see what is going on inside. In the top loader machine, you can open it at any time even when the machine is on wash mode but you cannot do so in front load machine, for the water will spill if you open the window on the washing mode. Otherwise, windows do not provide any other functional leverage to washing machines.
Quoted from http://www.why.do/why-do-washing-machines-have-windows/
Which actually does make sense. Since you can't see what's going on with your clothes from opening it, you need a window to be able to see.
As well as @Indofrasier answer, you can see if things are caught in it, if the cycle stopped for whatever reason, or if there's mechanical issues.
The first washing machines did not have a window. Then Louis Zimarik started creating washing machines with windows which were a great success. The idea behind the window was: Zimark found out that it was much easier to put a rubber seal around a glas door than a metal door. In addition he wanted to be able to check the operation of the machine. And therefor he needed a window.
Additionally people trusted a machine more where they can see what it is doing, when the washing machines where brand new and a bit "spooky" for the people. Today there is no technical reason for the glass door but it is being kept just because of the "traditional" reasons.
(german) source: http://www.sat1.de/ratgeber/waschmaschine-mit-fenster
His patents can be found here: https://www.google.de/search?tbo=p&tbm=pts&hl=en&q=ininventor:%22Louis+Zimarik%22
I call it a debug window, an almost life-saver in many situations:
Without debugging window, it would be hard to figure out the situations above.
The authors of the book Warum gibt es kein Katzenfutter mit Mäusegeschmack? asked Miele and Bosch, both German manufacturers of washing machines and dish-washers. These are their answers:
Miele
Bosch
You can see if anything is caught in the door seal so you can stop the cycle.
You can see if the water has emptied if there has been a fault, say from an electricity cut.
As the son of an ad man, I'd go with "Because the window is such a wonderful selling tool for the machine."
As an engineer, I'd go with "So you know whether there's a problem with unusually high water or suds level BEFORE you open the door and make a mess."
Neither of those is as much of an issue for a top-loader.
I think the comments in Mike's answer get the closest, but don't quite reach the reason. Most here seems to be forgetting that front-loading dryers also often have windows, so it's not solely a matter of the water.
This is something I have to deal with almost every single week:
The window lets me know beforehand when the spinning motion of the machine has accidentally piled my clothes up at the front of the machine. If I open the door without knowing the clothes were piled up, they are far more likely to fall out and onto the dirty floor. But because I can see them piled up as I approach the machine, I know they're positioned badly and I have to open the door slowly and catch them.
Dishwashers (hopefully) don't have anything flopping around where they can pile up against the door, so there's no need to see where everything is before opening the door.
I personally think it is for safety.
Since things move around there. What if some object accidently gets in there? A cat or a toddler? Or if something is left inside your clothes? Your cell phone. You would obviously catch a glimpse of it and turn the machine off.
I bet it's combination of two things:
A few years ago, I lived in a room that shared common areas with many other housemates. Included in these common areas was a Maytag Neptune washer. This was the first front-loading washer that I have ever seen WITHOUT a window. It threw me for a loop. The basket does have a slight tilt to it (maybe 15-30 degrees upward, compared to most which are straight), but any decent load would tumble out of the basket when the door was opened. Without the window, I feared my laundry would leap out of the basket and on to the floor.
Sidenotes:
Oduvan's answer is on the right track.
In the past, with earlier simpler washing machine models, you added starch or fabric softener at certain times during the wash cycle. The machines did not have special cups or dispense at right time; they did not have timed cycles that paused or beeped. They were a simple tub that filled with water and whatever you added to it. The window was necessary so that you could see what cycle it was at to add starch or softener.
Old machines had a door at the top, it was virtually useless to have a window there since you can always open it. On the newer machines you can't actually know if you can open the door w/o a window since there still may be water inside despite of what you might assume from the machine's indicators.
I got reminded of this "fable" from when elevators were first introduced in tall buildings like skyscrapers. They made some "user research" tests and people shared that they felt like those things went up and down way too slow.
So after some thinking, they installed mirrors inside and in the waiting area to serve as a distraction. As an effect people reported they weren't as discontent with the speed of operation, they felt like time passed faster when they had a distraction like a mirror. It also served as a countermeasure for the feeling of claustrophobia.
Probably the same rationale went into putting a window on microwaves. Watching what's going on with your food helps with waiting for it for a minute or two. And that window required some engineering to produce. The microwave radiation would escape through glass, so it needs a metal mesh on the inside to form a perfect Faraday's cage. That's also why it's somewhat semi-transparent.
The window is there to demo the unit in the store and improve sales over units that don't have a window. Stores would place material inside and leave it running in a high traffic area to get the product more attention. Most high end washers have a demo mode that cycles threw the different wash modes in a short repeating sequence.
Top loading washers don't have a window because you can't see inside when you walk past a demo unit.
The trend for front windows is the result of competition among brands seeking prime space in retail stores. As more brands offer easier models to demo fewer where selected by retailers to run in demo mode.
Front loading washers use to be a premium home appliance, but they've become much more affordable as governments enforce water conservation laws for washing machines.
To differentiate front loaders from low-end and high-end brands. Manufactures have to introduce new gimmicks that make the appliance demo better in the stores. As a result, we now see touch controls, fancy dials, touch screens and other such gimmicks.
It's all about sales...
