Lesson4: Pearl Processing Workflow
a. Sorting
Pearls are categorized based on their quality into different grades: those suitable for sale, those with potential for further processing, and those without processing value.
b. Cleaning
The pearls are cleaned to remove surface impurities. For example, Akoya pearls are cleaned by soaking them in saltwater to eliminate tiny impurities such as cellular tissue.
c. Drilling
Holes are drilled into the pearls to remove some surface imperfections and to allow chemical agents to penetrate the pearls during subsequent processing, speeding up the reactions.
d. Bleaching
This process removes surface stains, pigmentation, and reduces imperfections, resulting in a more uniform, whiter appearance or enhancing the natural color of the pearls. For instance, Akoya pearls often have a greenish tint when first harvested, which can be removed using hydrogen peroxide.
e. Luster and Whitening Enhancement
Brightening and Whitening: Fluorescent brightening and whitening agents are used to remove chemically stable pigments from the pearl surface.
f. Polishing
The goal is to smooth the surface of the pearls without altering their shape. The speed of polishing and the choice of polishing materials are crucial for determining the quality of the polish. A variety of polishing materials are available, with walnut shells and corn cobs being commonly used.