Homogenising of the melt is usually the most difficult and time consuming stage of glass melting. Flow stretches and aligns inhomogeneties in glass melts, rotating them towards the direction of flow. This accelerates homogenising by decreasing the distances over which diffusion must occur both within and outside the inclusions, both of which shorten times to achieve acceptable homogeneity. Alignment parallel to the direction of flow also generally minimises the optical distortion of images seen through the final product which is caused by cord or ream. It is shown that viscosity has a considerable effect, more viscous inclusions deforming more slowly. The final shape and orientation of such miscible inclusions depends on the total amount of shear to which they have been subjected.
