Brass doorknobs (or any other brass objects) sterilise themselves after about 8h since bacteria have a hard time surviving on brass. This is called the Oligodynamic Effect.

Oligodynamic effect

Silver spoons self-sanitize due to the oligodynamic effect

The oligodynamic effect (from Greek oligos “few”, and dynamis “force”) is a biocidal effect of metals, especially heavy metals, that occurs even in low concentrations. The effect was discovered by Karl Wilhelm von Nägeli, although he did not identify the cause. Scholarly texts from ancient India promoted the use of Brass and Silver in ritual cleansing practice as well as in consumption of food and drink. The ancient text Sushruta Samhita promoted the use of certain metals for early surgical procedures. Brass doorknobs and silverware both exhibit this effect to an extent.


The metals react with thiol (-SH) or amine (-NH(1,2,3)) groups of proteins, a mode of acti… Continue Reading