How to engineer a reverse explosion

Safe­ty pre­cau­tions

Ob­serve safe­ty rules when work­ing with heat­ing de­vices.


  • emp­ty alu­minum can;
  • heat­ing de­vice;
  • bowl of cold wa­ter;
  • heat-re­sis­tant gloves;
  • 10mL wa­ter.

Step-by-step in­struc­tions

Pour 10mL wa­ter into an emp­ty alu­minum can. Place the can on a heat­ing de­vice, such as a small stove with a can­dle, and heat it un­til a large amount of steam is re­leased. Put on a heat-re­sis­tant glove. Quick­ly put the can up­side down in cold wa­ter. Ob­serve as the can "ex­plodes" in­wards!

Process de­scrip­tion

Such an in­ward ex­plo­sion is known as im­plo­sion. When the can is heat­ed, the air in­side it ex­pands, and some air is forced out. As the wa­ter in the can be­gins to ac­tive­ly evap­o­rate, the form­ing va­por dis­places even more air. The sum of the pres­sures of the re­main­ing air and wa­ter va­por is equal to at­mo­spher­ic pres­sure. When the can is cooled, the pres­sure in­side falls and be­comes low­er than the out­er at­mo­spher­ic pres­sure, which crush­es the can. This ef­fect is en­hanced by the con­den­sa­tion in­side the can.