Mysterious chemical drawings

Science draws with an invisible hand – discover how it’s done!

Safe­ty pre­cau­tions

Warn­ing! Only un­der adult su­per­vi­sion.


  • wa­ter­col­or pa­per;
  • black-and-white im­age of a skull;
  • so­lu­tions of cop­per sul­fate;
  • am­mo­ni­um car­bon­ate;
  • potas­si­um io­dide;
  • iron(II) sul­fate and tan­nin;
  • plas­tic skele­ton;
  • cof­fee fil­ter.

Step-by-step in­struc­tions

Ap­ply a cop­per sul­fate so­lu­tion to the eye sock­ets of a black-and-white im­age of a skull. Leave the im­age over a so­lu­tion of am­mo­ni­um car­bon­ate – sud­den­ly the skull’s eye sock­ets start turn­ing blue!

Ap­ply a so­lu­tion of potas­si­um io­dide to wa­ter­col­or pa­per. Dip a plas­tic skele­ton’s feet in a cop­per sul­fate so­lu­tion. Now if this skele­ton walks on the pa­per, it leaves dark foot­prints be­hind!

Use a tan­nin so­lu­tion to draw an in­vis­i­ble skull on a cof­fee fil­ter. Leave it in an iron(II) sul­fate so­lu­tion. The liq­uid starts ris­ing to re­veal the in­vis­i­ble skull!

Process de­scrip­tion

Am­mo­ni­um car­bon­ate de­com­pos­es to re­lease a gas called am­mo­nia. These gas mol­e­cules bind to cop­per ions, yield­ing a new dark blue com­pound. Share the re­sults with our teach­er via the MEL Sci­ence app!

Cop­per sul­fate can also re­act with potas­si­um io­dide. This time, it yields molec­u­lar io­dine and a dark brown tri­io­dide com­plex.

The an­tiox­i­dant tan­nin pos­sess­es a lot of spe­cial frag­ments that can trap iron(II) ions. This cre­ates a new com­pound with a dark vi­o­let col­or.

Ul­ti­mate­ly, none of these im­ages ap­peared on their own – they were drawn by the "in­vis­i­ble hand" of sci­ence!

Sim­i­lar ex­per­i­ments are in­clud­ed in the “Chem­istry for spies” set from the MEL Sci­ence sub­scrip­tion.