Cleaning pearls...there are several ways...and experts don't always agree on the best method.
Here, pearl expert, George Kunz, along with Charles Stevenson share what they feel is the best way.
For cleaning pearls, first rub them with a cloth dipped in alcohol diluted with warm (not hot) water, or in a weak solution of soap and water, then dip another cloth in clean water and rub the pearls until they are dry.
Be careful not to leave them wet. Either salt, rice, pearl-powder, or some exceedingly soft substance may aid in cleaning them, but no abrasive such as ground pumice, electro-silicon, or any powder that is sold as a polishing powder, should be used.
There are many things that will cause injury to pearls.
Occasionally they are affected by the wearer having exudations from the skin induced by some disease or else by acids which pass out through the pores with the perspiration.
A smoky atmosphere in which a sulphuric acid is present owing to sulphur in the coal, violent usage such as knocking severely, or dropping--all of these will in time cause more or less injury to a pearl, more especially to one of the whiter varieties; but it is believed that those of a yellowish cast are not so susceptible. Diderot mentioned this as early as 1765.
If there be any foundation for the belief that it is not well to lock pearls in a safe-deposit box, this is probably owing to the fact that the absolute exclusion from the air may cause the drying out of the organic constituent of the pearl.
This may be obviated by putting the pearls in a piece of linen absolutely free from any chemical, at the same time placing with them a bit of blotting -paper or fiber-paper saturated with water; the whole should then be wrapped up in paraffin paper, which will prevent the evaporation of the moisture.
I've also noticed that in fine pearl jewelry stores small glasses of water are placed inside of the jewerly display cabinets to prevent drying out of the pearls.More "How To" pages.Another method for cleaning pearls.