Bead Nuclei Production in Vietnam

Bead Nuclei Production in Vietnam

HaLong Bay in northern Vietnam is where most of the pearl farms are working. HaLong Bay is a UNESCO World Heritage Site and the pristine waters are a major component of this industry. I traveled to HaLong Bay in 2011 to visit pearl farms.

Vietnam has farmed pearls since the 1990s. When the harvest is good, the quality is very high. As well, when the harvest is bad the production is subpar. The companies that manage the pearl farms are trying to find ways to control the quality of their production. 

One of the most important aspects of pearl culturing is the sourcing of a quality bead nuclei that will be implanted in the oyster along with a tiny piece of mantle tissue to start the pearling process. The selection of a pure white bead is critical to the successful farming of pearls. Ideally, the best shell from which to make bead nuclei is freshwater shells from Kentucky Lake in Tennessee. 

In 2018, Devhand Chodhruy started his own production of bead nuclei in Vietnam to supply his pearl farms with a constant supply of high quality bead nuclei. He imports the raw shells in huge containers from Tennessee and processes them in Vietnam.

Upon receipt at the facility, the staff remove the shells from the bags and sort them into separate piles according to species. Processing begins with each half (valve) of the whole shell being sawn into two pieces. The thickest portion, from which the largest beads can be fashioned, is separated for use in the next step, which involves cutting each new portion into strips. A machine containing evenly spaced blades then cuts the strips into separate cube-like pieces. Staff use vertical blades to round the corners of the larger cubes in preparation for the next step in the process, which is grinding the final spherical beads between two stone discs. The smaller cubes used for the small nuclei do not warrant such painstaking attention, so they move to another machine that automatically rounds them to the desired form. Next, the large and small preformed nuclei are sized by sieving and then pass on to a grinding process that involves a series of stone discs of different grain sizes, from coarse to fine grain, to finalize the shaping. The discs arrive at the factory unscored, so another step in the process is to create the evenly spaced grooves in which the shell bead nuclei eventually sit. This is done by placing metal ball bearings onto the correctly sized ring-shaped template base. The new blank disc is lowered so that the ball bearings make contact with it, eventually creating grooves in the new disc. Water is applied throughout the process.

After the grinding work is complete, the nuclei pass on to a room where a staff of predominantly women sit with Perspex-based trays on their laps and another group sits at a table with closed-sided trays. The trays are gently rocked from side to side to make the nuclei with the most perfect symmetry (roundness) roll into a basket on the floor. Nuclei that do not make the grade—the ones that do not roll smoothly enough—are removed by hand and returned to the previous grinding step, where their size is sacrificed for the sake of a more precise shape. Roundness is then double-checked using the closed-sided trays , and once they pass this step, nuclei are transferred to two wooden barrels, where they are exposed to a weak acid treatment. The acid removes the powdery surface texture and, in effect, polishes them into a final product. The proprietary acid bath step is very important. Too strong an acid will cause the shell to crack and etch too quickly, while too weak a solution will not effectively smooth the bead surface.

Next in the nuclei’s journey comes a final check of the shape precision and color/imperfection grading so that they may be sorted into high-quality nuclei lots with matching grades for use in specific farms around the world depending on requirements (refer to earlier comment on color/imperfections and types of mollusks on farms). The shape is checked one final time using a machine (figure 4F) developed by the Chinese pearl industry that has been slightly modified and is manufactured in Vietnam. It consists of two stacked rotating glass discs with simple boundary walls that allow the beads, which gently drop from the hopper onto the outer surface of the first glass disc, to roll along. If the nuclei are perfectly spherical, they will follow the wall and drop into a basket and pass the test. If, on the other hand, there are any small flat or uneven surface areas, they will not roll smoothly and will travel away from the wall in keeping with the motion of the rotating glass. Those that fail eventually exit on the opposite side of the disc and are taken back to the grinding step. It was very evident that the speed of the glass discs was critical to this part of the process and had to be continuously monitored. The Witco team was working to make the speed more consistent or at least reduce the range of speed, for variability is sometimes needed depending on the bead size.

Color/imperfection sorting, the last step in the process, takes place in the same room as the machine with the stacked glass discs. Nuclei are examined and split into groups of varying degrees of whiteness. The whiter the nuclei, the better the quality and the higher the selling price. Discussions made it clear that the factory’s work has just begun and they already supply nuclei to quite a few farms. Production will be increased as steps in the process allow, and different sized nuclei will continue to be produced, although all the smaller nuclei are destined for the farms operated by Orient Pearls (Bangkok) in Vietnam. The more banded or off-white nuclei are typically sent to existing clients for the production of Tahitian bead cultured pearls, where the whiteness is not as critical as in Japanese and Vietnamese akoya production. It was interesting to learn that the maple leaf mussel produces the purest white beads needed for akoya production, while the washboard mussel produces the more banded and hence less expensive nuclei that are acceptable to the Tahitian pearl farmers and farms where golden Pinctada maxima are produced.

By the end of the visit to the factory, it was apparent that the roundest shape and whitest color were the paramount objectives in nuclei production. Obtaining these two goals, however, requires considerable experience, trial and error, investment, and adaptability. It was also very surprising to learn that only 3.5–4% of the imported shell leaves the factory as nuclei. The target is to produce 5% or more, but that still means that much of the original shell is not suitable for nuclei or is wasted, further underscoring the challenges of nuclei production.

Thank you to GIA field trip in 2018 for the current information of bead nuclei in Vietnam.

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