Figure 5.31 shows the convective field in the form of schlieren images. A well-defined plume rising from the top surface of the crystal is seen at both times of t=2 and 30 hours for four view angles. At t=2 hours, the plume was temporally stable, though a swaying movement was seen from one projection angle to the other. The swaying motion was due to the disturbance of the flow field caused by the turning of the growth chamber for recording the projection data. The tilt in the plume at selected angles for small time is also related to the non-symmetric shape of the initial crystal itself. At a later time (t=30 hours), the gradients are large enough to give rise to a stable and symmetric convective field. This is accompanied by uniform deposition of the solute on the crystal surfaces. As discussed in Section Growth Patterns in The Diffusion Regime, this regime yields the highest quality of the crystal in terms of symmetry of the faces and its transparency, along with the fastest growth rate. 

Figure 5.32: Concentration contours around a growing crystal in the presence of well-defined convective plume for the four view angles at two different time instants