Caitlin said:
And some graft materials do not leave impressions of themselves? I wonder why that would be?
Good question. I suppose the short answer is like snowflakes. No two are identical. The experience and technique of the grafter is certainly reflected in the overall quality of the harvest. As we know, the ratio of imperfect to perfect is often greater than 10:1, so even with the most diligent surgery and husbandry, things can still go awry.
Catlin said:
What happens to the equivalent graft material in nucleated pearls?
The ideal pearl would be one where the mollusc didn't concrete the graft to the bead before the sac is fully formed. The quality of the bead is reflected in the finished pearl. It's nearly impossible to get a round pearl from an off-round bead or get a smooth nacreous surface from a rough bead. This is why some shells are preferable over others, namely American mussels for their thickness and tight extracrystalline structure.
Let's imagine for a moment we want to paint a basketball. If we spray painted it, the ridges and bumps will still remain pronounced in their original patterns, even after several layers are applied. If we were to dip the ball in paint, it would round out some of the angles, but the overall patterns would still be visible. Likewise it could develop drips or a ring/flatspot at the base. If we used a brush, it could leave brush marks.
Perfectly round non-beaded pearls, such as freshadamas are exceedingly rare and are merely the luck of the draw when selected from enormous pools of pearls. I've never witnessed freshwater grading operations before, but would hazard to guess the ratio is far greater than 1:1000.
Caitlin said:
How do they keep all that cellular material that is not epithelial cells on the outside of the sack after the sack forms?
They don't. Sometimes it's dissolved, sometimes it's encapsulated in a cyst or sometimes it's calcified and concreted as part of the nucleus or the graft may be rejected for a whole host of possible reasons. Extraneous or foreign cells in grafts can lead gaseous pearls, which has been discussed here recently in Adeline's thread and supported by Augustus Collection. Douglas has published some info on gaseous pearls as well. Again, there are no absolutes here, because it's reasonable to expect that even precision grafts can get unruly.
Caitlin said:
Why is it different in non nucleated pearls? Does it only happen when the grafter puts too much excess material into the graft?
Perhaps, but not always. Too little graft tissue where transplanted cells didn't take is also likely to fester. The remaining necrotic cells could become calcified and form a nucleus, but the process is delayed and the pearl will be smaller than other grafts the same age. Stunted, as it were, yet still viable as a pearl. The only difference between the two processes, is the bead and graft by virtue of their proximity to each other, trigger the epithelial cells to layup aragonite, where in non-beaded, the cells have to create it's own nucleus first.
The real beauty of discovering and studying natural pearls, is I am able to compare the growth of the pearl to the growth of the shell, which often match the patterns in latter layers of the shell. By this method, one can confirm the age of a natural pearl. This is why I find working with conjoined pearls intriguing, because they are pearls within pearls and created by often different means.
