In the new pearl optimization process, pretreatment is as important as bleaching, and its purpose and treatment method are different from the old process, which is mainly designed for how much pearl luster will be destroyed by the old process. The main purpose is to protect the solidified nacre from damage during bleaching and polishing. The main steps are cleaning, not punching, protecting nacre, finishing and punching. Among them, the treatment of non-perforated protective bead layer is its characteristic. The effect of pretreatment is to prevent the pearl surface from direct contact with bleaching solution, avoid oxidative damage and enhance the luster of pearl. The mixture of benzene and ammonia water is omitted, and the newly adopted reagent is not described because the process is confidential.
In order to achieve the above objectives, it is required that the reagents used must be colorless, transparent, heat-resistant, acid and alkali-resistant, chemically stable, and have no side effects on human body, and can withstand ultrasonic cleaning and polishing.
The characteristics of bead protection layer treatment are: 1, no perforation; 2, the brightness is obviously enhanced; 3. In the bleaching process, a large number of splashing bubbles will not be attached to the pearl surface.
Second, bleaching
2. 1 decontamination treatment
Cultured pearls are not inherently complete. During its growth, organic impurities such as free cells in the mother shell, mucus secretion, and necrotic parts of the outer membrane are wrapped between the pearl layer and the pearl core or between the pearl thin layers, so that more than 90% of pearls directly obtained from the mother shell are dirty pearls with different degrees of black spots, which seriously affects the luster of pearls. Therefore, pearls must be treated before they can be used for decoration. Decontamination and bleaching can restore the original luster of pearls and is a key link to increase the value of pearls.
Besides bleach, the best formula of decontamination and bleaching is composed of solvent, penetrant, stabilizer, surfactant and other additives. The selection, dosage and composition of various reagents are the key to determine the bleaching quality. When used properly, its bleaching effect is good; Otherwise, the pearl will deteriorate. Damaged pearls.
There are two kinds of surfactants, ionic and nonionic. In pearl bleaching, nonionic interface activity is the best, such as Span and Tween. Although the dosage is only one thousandth, it plays a special role in wetting, infiltration, diffusion and washing.
Stabilizers are mainly used to adjust and control the PH value of bleaching solution, because the main chemical component of pearls is calcium carbonate, which will corrode pearls if the solution becomes acidic. Although the PH value of the bleaching solution has been changed by alkali in the pearl bleaching process, the PH value usually decreases with the bleaching process, so the selection and stability of the PH value of the bleaching solution in the pearl bleaching process is very important.
There are no large number of bubbles attached to the surface of pretreated pearls during bleaching, which is different from the old process. The bleaching solution does not directly contact the pearl surface, but enters the inner layer of the pearl from the pearl hole, and reacts with the coloring substance to decolorize the pearl, thus eliminating the possibility of "walking" on the pearl surface and pearl damage.
Bleaching temperature is controlled in low temperature system. Although the bleaching time is prolonged, the bleaching is thorough and effective, and the pearlescent damage rate is extremely low.
2.2 dehydration treatment
Dehydration treatment refers to cleaning pearls and removing bleaching solution remaining in pearls. At present, although the principle of pearl yellowing is still inconclusive, it is found in experiments that pearls without dehydration treatment will appear turbidity, white spots and slow yellowing, which will affect the quality of pearls, so dehydration treatment is more important.
Third, post-processing.
In order to further improve the luster of pearls, pearls after decontamination and bleaching generally need post-treatment, that is, whitening, color matching and polishing, which can be flexibly selected, among which polishing is the most important.
Four. conclusion
Pearl processing technology can improve the quality of pearls to the greatest extent, and its uniqueness lies in:
1. Pretreatment of non-perforated protective bead layer;
2. Low temperature system for bleaching;
3. Selection of emerging polishing materials.