Negative Staining- Principle, Reagents, Procedure and Result 3.95/5 (38) Negative Staining- Principle, Reagents, Procedure and Result. The main purpose of Negative staining is to study the morphological shape, size and arrangement of the bacteria cells that is difficult to stain. eg: Spirilla. It can also be used to stain cells that are too delicate to be heat-fixed.