Peter T. Daniels
2017-11-30 17:56:38 UTC
Yesterday I heated a bag of frozen vegetables (that I had accidentally brought
home instead of a "Steam-in bag"), by placing the contents into a microwave-
save plastic bowl (squarish with rounded corners), adding 1/4 cup water (per
the instructions), and putting on the lid attached by friction at two or three
of the corners, leaving the fourth unattached so that the steam could vent (as
when using a "steam-in bag," which puffs up during the zapping and deflates
during the cool-down time). When the cooking was done, the bowl was badly
deformed -- and the lid tightly attached at all four corners (and all around).
Removing the lid was not overly difficult, and there was no burst of steam; the
bowl recovered its usual shape; the contents were packed into less than the
volume they ought to have occupied.
Where did the vacuum come from?
There was much more liquid at the bottom than with a "steam-in bag," which
suggests that the lid sealed itself early in the process so that steam couldn't escape.
home instead of a "Steam-in bag"), by placing the contents into a microwave-
save plastic bowl (squarish with rounded corners), adding 1/4 cup water (per
the instructions), and putting on the lid attached by friction at two or three
of the corners, leaving the fourth unattached so that the steam could vent (as
when using a "steam-in bag," which puffs up during the zapping and deflates
during the cool-down time). When the cooking was done, the bowl was badly
deformed -- and the lid tightly attached at all four corners (and all around).
Removing the lid was not overly difficult, and there was no burst of steam; the
bowl recovered its usual shape; the contents were packed into less than the
volume they ought to have occupied.
Where did the vacuum come from?
There was much more liquid at the bottom than with a "steam-in bag," which
suggests that the lid sealed itself early in the process so that steam couldn't escape.