A mild bleaching process is used to clean the surface skin and remove any residues. They then undergo a light polishing using crushed walnut shell to “buff up” their inherent lustre.

Poor quality, misaligned drilling will reduce the value of even a fine pearl, so care still has to be taken at this stage. A technician only has one chance to get it right.

This is with the exception of South sea pearls which are generally left undrilled until the after they are sold by lots.

Knotting, as well as adding length, removes the risk of losing all but one pearl should the row break.