Suction glass

How to make a suction glass

How can you turn an or­di­nary glass into a suc­tion de­vice?

Safe­ty pre­cau­tions

None.

Equip­ment

  • tray;
  • glass;
  • can­dle;
  • nap­kin.

Step-by-step in­struc­tions

Put a nap­kin on a flat tray and moist­en it with wa­ter. Place a can­dle in the cen­ter of the nap­kin and light it. Cov­er the can­dle with a glass and press down hard to en­sure a good seal. When the can­dle goes out, the glass will stick to the tray so se­cure­ly that you’ll be able to use it to lift the weight of sev­er­al fruits!

Process de­scrip­tion

The can­dle flame heats the sur­round­ing air. When cov­ered by the glass, the tem­per­a­ture of this air is al­ready above that of the am­bi­ent air. The amount of air in­side the glass doesn't change, and its ini­tial pres­sure is equal to at­mo­spher­ic. As the can­dle burns, it con­sumes oxy­gen, and af­ter a while the con­cen­tra­tion of oxy­gen in­side the glass is no longer suf­fi­cient to sus­tain com­bus­tion. Though the can­dle con­tin­ues to heat the air, it will go out be­fore the pres­sure in­side the glass ris­es enough to cause any vis­i­ble ef­fects. Af­ter the can­dle goes out, the gas in­side the glass cools to am­bi­ent tem­per­a­ture; mean­while, its pres­sure drops, be­com­ing much low­er than that of the air out­side the glass. This pres­sure dif­fer­ence caus­es the glass and the tray to press firm­ly against each oth­er.