One problem my roommates and I have is figuring out whether the dishes are dirty or clean. How could you design a dishwasher to always tell whether the dishes inside are clean or dirty? How can we work around the current dishwasher design to figure out whether the dishes are clean or dirty?

  • 2
    You can usually tell by looking at the dishes. Barring that, newer dishwashers usually have some sort of status display indicating the cycle is finished.
    – DA01
    May 2, 2012 at 5:53
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    FWIW, I disagree with closing this, There is a clear question here, and it does relate to physical person-machine interfaces. It could do with some enhancement, but I think there is a good question in here May 2, 2012 at 8:02
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    this is one of those google interview questions, isnt it? How could you weigh an elephant without scales etc etc? how do you know if the firdge door light has gone out once you've closed the door?
    – colmcq
    May 2, 2012 at 12:06
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    I also think this is a legitimate design question.
    – PhillipW
    May 2, 2012 at 13:07
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    The lack of integration of electronics in kitchens is quite depressing: what's needed are appliances which can talk to smart phones.
    – PhillipW
    May 2, 2012 at 15:39

1 Answer 1


Weigh the dishes. A dishwasher that had a built-in scale could tell when something had been added rather than taking out. If the weight increases while the door is open, then the contents are dirty. If the weight has only decreased so far, then everything is still clean. This would fail on edge cases like taking out a clean dish and putting in a dirty one at the same time, but most people don't pretend to be Indiana Jones while managing their dishes.

  • It is important to note that Indiana Jones didn't make the switch right (it is for the audience to try and recall whether his bag of sand was too heavy or too light). But he was able to run fast though.
    – Amir Kirsh
    Dec 20, 2021 at 20:46

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