Home science: waterproof secret

How can you hide a message underwater without getting it wet?

Safe­ty pre­cau­tions

Warn­ing! Only un­der adult su­per­vi­sion.


  • glass con­tain­er with lid;
  • glass;
  • dou­ble-sid­ed tape;
  • mes­sage.

Step-by-step in­struc­tions

Fill a glass tank ap­prox­i­mate­ly half­way full with wa­ter. Tape a mes­sage to the bot­tom of a glass and fix the bot­tom of the glass to the in­ner side of the lid of the glass tank us­ing dou­ble-sid­ed tape. Gen­tly close the lid, im­mers­ing the glass, up­side down, in the wa­ter. When you open the lid and re­trieve the glass from the wa­ter, you’ll see that the mes­sage in­side is still dry! You can prove the pres­ence of air in the glass by cov­er­ing a can­dle with the glass and re­peat­ing the process – the can­dle will con­tin­ue to burn, de­spite the fact that the liq­uid lev­el out­side the glass is high­er than the flame.

Process de­scrip­tion

When the glass is im­mersed in wa­ter, it con­tains air. Wa­ter tends to push light air up­ward, com­press­ing it and trap­ping it in­side the glass, which pre­vents the wa­ter it­self from ris­ing to fill the glass. Your mes­sage is safe­ly hid­den in­side this air pock­et! You can choose won­der­ful chem­istry kits and get them on a month­ly ba­sis for your kids.

Many more cool ex­per­i­ments await you in the MEL Physics sub­scrip­tion!