Spectrum makes a good diastase of malt they call "Maltin" catalog number
DI104.
I use the diastase digestion method as described in the AFIP Laboratory
Methods in Histotechnology, where a phospate buffer solution is used in
place of distilled water. However, the DW has also worked fine. I typically
use a little more diastase than is called for--I've found that Spectrum's
diastase was a little weak. Be sure to refrigerate the dry diastase.

Jon Kerr
Histology Manager
Reference Pathology Services