Rainbow plating

Safe­ty pre­cau­tions

Warn­ing! Only un­der adult su­per­vi­sion.

Equip­ment

• cop­per(II) sul­fate so­lu­tion;
• metal­lic plate;
• sand­pa­per;
• ad­he­sive sten­cil;
• bowl of wa­ter;
• heat­ing de­vice;
• al­co­hol;
• cot­ton pad;
• col­or­less nail pol­ish.

Step-by-step in­struc­tions

Sand a steel plate and wipe it down with a cot­ton pad moist­ened with al­co­hol. Glue a sten­cil onto the plate. Ap­ply a so­lu­tion of cop­per(II) sul­fate. Af­ter 10 sec­onds, rinse the plate in a bowl of wa­ter. Care­ful­ly re­move the sten­cil and warm the plate on a heat­ing de­vice. This yields a rain­bow coat­ing, which can be pre­served with a pro­tec­tive lay­er of col­or­less nail pol­ish.

Process de­scrip­tion

Coat­ing the steel plate with the cop­per(II) sul­fate so­lu­tion re­sults in a re­dox re­ac­tion in which iron, as the more ac­tive met­al, dis­places cop­per from the so­lu­tion of its salt. In this case, the points of con­tact be­tween the so­lu­tion and the iron plate are cov­ered with a thin lay­er of cop­per. If this cop­per lay­er is heat­ed, a rain­bow film of cop­per ox­ides ap­pears. The col­or of this film varies de­pend­ing on how thick it is.

This and oth­er safe home ex­per­i­ments are wait­ing for you in the MEL Chem­istry sub­scrip­tion!