The tomographic X-ray technique (TEDDI) has been used to continue investigation into crystallite alignment and polymorphic content inside a model batch crystalliser. Previously, the beta-polymorph of glutamic acid was shown to exhibit zoning with a supernatant alignment band under stirring conditions, whereas the alpha-polymorph has now been shown to demonstrate very different behaviour; in particular, its prismatic crystallites appear to be more buoyant than the beta-form platelets and there are no apparent preferred orientation effects. In a mixed phase suspension, the beta-form appears to dominate, impeding the rise of the alpha-form in the vessel. In addition, investigation into the effects of crystallite size reveals that the larger beta-form crystallites are more buoyant than smaller crystallites. Higher resolution experiments confirm results seen previously in lower resolution intensity maps. (c) 2006 Elsevier B.V. All rights reserved.