Why Does Heating This Suck In The ClingFilm ?

  • 2 Replies
  • 2287 Views

0 Members and 1 Guest are viewing this topic.

*

Offline neilep

  • Withdrawnmist
  • Naked Science Forum GOD!
  • *******
  • 20602
    • View Profile
Why Does Heating This Suck In The ClingFilm ?
« on: 13/11/2007 17:02:37 »
Dearest Peeps Of International Plastic Wrapping Fun & Luff,

See this bowl of yummy veggies ?


[attachment=1488]

Nice isn't it ?..Notice how veggy like and ready to be zapped by microwave hugs they are ?


But, when ewe heat it.....heat expands yes ?....the clingfilm expands to create a dome......so why does the clingfilm get sucked in onto the vegetable AFTER the cooking is done ?..surely it should continue to expand or maintain it's dome like structure eh ?


I've sent an email via a Medium to Sir Christopher Wren ( he's an authority on domes)...but I got an 'out of office' reply !!

Can ewe help me ?


Men are the same as women, just inside out !

*

lyner

  • Guest
Why Does Heating This Suck In The ClingFilm ?
« Reply #1 on: 13/11/2007 18:15:26 »
Loadsa pressure when the water inside's boiling.
This forces some steam and air out past the film / bowl gap.
When it cools, the steam condenses and the pressure is lower - atmospheric pressure pushes in and, because it is pushing inwards on the (by now soft) film, forms a better seal than before and keeps the pressure inside, low. Hence the dome.
They always tell you to put a tiny hole in the film to stop the vacuum-pak effect.

*

Offline neilep

  • Withdrawnmist
  • Naked Science Forum GOD!
  • *******
  • 20602
    • View Profile
Why Does Heating This Suck In The ClingFilm ?
« Reply #2 on: 14/11/2007 12:56:50 »
Loadsa pressure when the water inside's boiling.
This forces some steam and air out past the film / bowl gap.
When it cools, the steam condenses and the pressure is lower - atmospheric pressure pushes in and, because it is pushing inwards on the (by now soft) film, forms a better seal than before and keeps the pressure inside, low. Hence the dome.
They always tell you to put a tiny hole in the film to stop the vacuum-pak effect.

THAN YOU THANK YOU THANK YOU very much !!....I understand !!

YAYYYYYYYYYYYYYYY !!
Men are the same as women, just inside out !