Maeshori
The Japanese pre-treatment given to pearls after harvest to bring up lustre before they are sold.
Maeshori means pre-treatment. It covers a range of proprietary processes using alcohol, salts and controlled temperature to condition the nacre.
Done well it genuinely improves lustre and is permanent. Done aggressively it produces a temporary shine that dulls within a couple of years.
Because methods are trade secrets, maeshori is rarely disclosed in any detail, even between wholesalers.
When you are buying
This is one reason to buy pearls from a seller who handles them regularly rather than the cheapest listing. Over-treated pearls look excellent on the day and disappoint later.
Bleaching
A standard post-harvest treatment that evens out a pearl's colour and lightens it. Near universal in Akoya.
Lustre
How sharply a pearl reflects light. The single most important quality factor, and the one you can judge without any training.
Nacre
The material a pearl is made of: microscopic aragonite platelets glued in layers by conchiolin. Thickness determines both lustre and lifespan.
Akoya Pearl
The classic small round white saltwater pearl from Japan and China, usually 5mm to 9mm. The pearl in a traditional single-strand necklace.
Hanadama
A Japanese certification for the top tier of Akoya pearls, issued by an independent laboratory rather than a seller.