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When you put a duvet cover in a washing machine without buttoning it up any other items of bedding (e.g. pillow cases) inevitably end up inside it. Instinctively, I would think that the opposite would happen (although I have no rigourous basis for believing this) due to the contents of the duvet cover being pushed out of it as it rotates. Why does this (to me at least) counter-intuitive behaviour occur? (Or are my findings not reproducible?)

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    $\begingroup$ I think it's statistical: items flop all over, but once inside the cover (happens to me with fitted sheets) they can't get out again. $\endgroup$ Jan 4 '14 at 16:19
  • $\begingroup$ @CarlWitthoft But surely something is as likely to move into the duvet as out of it (unless it is completely full)? $\endgroup$
    – rlms
    Jan 4 '14 at 16:37
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From the Dutch National Science Quiz 2006 (my translation):

Question 14: You put a duvet cover together with smaller laundry in the washing machine. Why, at the end of the program, all smaller laundry has twisted itself in the duvet cover?

Due to the left-and-right cycling of the drum

Washing machines predominantly cycle one way. To loosen the laundry, the drum sometimes abruptly turns the other way. Due to this opposite movement, suddenly a few liters of water bumps very forcefully into the laundry, and therefore the opening of the duvet cover will come to lie completely open. Smaller laundry falls in one piece at a time. As soon as the machine goes into centrifuge mode, the smaller laundry pieces are being pushed in further. It is very difficult for laundry that is in the duvet cover to get out.

NB: The false answers were (my translation):

Because small laundry pieces are more sensitive to water vortices than large items

Due to the area (size) difference between the duvet cover and smaller laundry


I would like to add, from personal experience, that it is very rare that all smaller laundry ends up in the cover. Sometimes half of it will get in there, and sometimes just the odd sock. But perhaps that's just me and my machine.

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    $\begingroup$ The Google Dutch-English translation was understandable and might be a reasonable starting point. $\endgroup$
    – DWin
    Jan 4 '14 at 17:11
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Perhaps: once the duvet gets packed by items by chance, the friction in between the items and due to inside of the duvet hampers the return of the items to the outside. It is a "trap" for items:-)

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  • $\begingroup$ Some fish netting works as such a trap. $\endgroup$
    – Urgje
    Jan 4 '14 at 21:45

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