Over the year, sebum accumulates on note's surface, reacts with oxygen in the air and turns a yellowish hue, said the study published in the journal Industrial and Engineering Chemistry Research.
Lawandy and his team decided to see if they could just clean it by removing the accumulated sebum.
They turned to 'supercritical' CO2 - that acts both like a gas and a liquid and is commonly used in other cleaning applications.
