Carmine Alum Staining Protocol

Carmine is a commonly used stain in histology used by early botanists such as John Hill in their studies in 1770s. The stain was used to study microscopic tissue structures when in ammoniacal solution form and it is still used today in histologic studies. Carmine staining, however, can be an alternative to hematoxylin counterstaining of immune-stained tissue sections. A variety of carmine formulations exist for very clean and sharp nuclear staining.

• Carmine stain preparation. Place 2.5 g Alum potassium sulfate and 1.0 g Carmine to 500 ml dH₂O. Boil for at least 40 minutes and keep hot. Filter through paper and adjust to final volume of 500 ml. There will be a lot of stain that doesn't dissolve. This can be minimized by keeping the solution boiling while filtering a small amount at a time.
• Carnoy's fixative preparation. In a fume hood pour 60 ml of ethanol into a suitable container, add 30 ml chloroform and 10 ml glacial acetic acid to give a total volume of 100 ml.
• Spread tissue on glass slide and fix in Carnoy's fixative for 2 to 4 hours.
• Wash in 70% EtOH for 15 min, change gradually to distilled water, rinse in distilled water for 5 min.
• Stain in carmine alum stain, wash in 70% EtOH 15 min, 95% EtOH 15 min, and 100% EtOH 15 min.
• After photographic documentation, the tissue can be embedded in paraffin for sectioning and conventional histological staining.

• The extraction action should be rapid and should not be delayed for too long, to avoid changes in the composition and structure of the tissue cells.
• Before staining, it is important to understand the preparation method of the staining solution used, as different staining solutions are processed differently after staining.
• The time used in the staining process should be flexible according to the room temperature, the freshness of the staining solution and the actual situation in the laboratory at the time of staining.

Special Staining Services

Immunohistochemistry (IHC), Immunofluorescence (IF) Service

Transmission Electron Microscopy (TEM) Service