There is much more phosphotungstic acid in the solution than hematein. The phosphotungstic acid binds all of the available hematein to form a blue lake pigment. This lake stains the muscle cross striations, fibrin, nuclei, and other tissue elements blue. The rest of the phosphotungstic acid stains the red-brown components, such as collagen.[2]
Staining procedural notes
Zenker fixative is preferred, although formalin fixed tissue can be used. If this is the case, the tissue should be mordanted in Zenkers solution before staining. Most texts recommend mordanting in Zenker fixative overnight at room temperature, but it can be done for 3.5 hours in a 56 to 60 degrees Celsius oven.
PTAH solution, Gram Iodine, 5% sodium thiosulfate, 0.25% Potassium Permanganate, and 5% Oxalic Acid solution are needed.[2]
After staining, slides should be dehydrated quickly because the red-brown components lose their color when exposed to water or alcohol.
Vargas SO; Sampson BA; Schoen FJ (June 1999). "Pathologic detection of early myocardial infarction: a critical review of the evolution and usefulness of modern techniques". Mod. Pathol. 12 (6): 635–45. PMID10392641.