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Electron Microscopy Sciences

Technical Data Sheets

Alcoholic Congo Red Solution

EMS Catalog # 26090-05 & 26090-06

Benhold’s Method for Amyloid


10% Buffered Neutral Formalin


Cut paraffin 6 microns (12 microns for thicker sections, minute amyloid deposits with Congo Red, Sirus Red, Crystal Violet Stains)


  1. Deparaffinize and hydrate to distilled water
  2. Stain 10 minutes in Mayer’s Acid Hemalum (#26853). Wash in three changes of distilled water
  3. To 40 ml of stock Alkaline Alcohol (#26385) add 0.4ml Sodium Hydroxide 1% (#21172) just before use. Transfer sections to alkaline alcohol for 20 minutes
  4. Stain 20 minutes in freshly alkalinized Congo Red Solution (#26090-05): to 40 ml Stock Congo Red Solution add 0.4 ml Sodium Hydroxide 1%. Filter and use within 15 minutes.
  5. Dehydrate quickly in three changes of absolute alcohol. Clear through two changes of Xylene (#23400). Mount.

Congo Red (Benhold’s) Method for Amyloid Standard and Microwave Procedure Staining:

  1. Deparaffinize and hydrate to distilled water
  2. Stain in filtered Congo Red, 1% Aqueous (#26090) for 1 hour
    If using microwave stain in Congo Red, 1% Aqueous (#26090) for seconds. The hot stain  jar is removed from the oven and allowed to stand at room temperature for 60 seconds
  3. Rinse in distilled water
  4. Differentiate rapidly in Alkaline Alcohol (#26385)
  5. Wash in running tap water for 5 minutes
  6. Counterstain in Mayer’s Hematoxylin (#26602)for 5 minutes
    If using a microwave oven  - stain in microwave for 30 seconds
  7. Wash in running tap water for 15 minutes
  8. Dehydrate and clear through 95% ethyl, absolute alcohol changes, 2 minutes each
  9. Mount using resinous medium

Stain results:

Amyloids Pink Red
Nuclei Blue
Elastic Tissue Light Red


Clark G. : Staining Procedures, Williams and Wilkins Co. , Baltimore  C 1973, p. 49 Puchtlere, H. & Sweat, F. : J. Histochem., 10:355f (1962)

Online Ordering

Alcoholic Congo Red Solution is available online from the EMS Catalog. For ordering or product information, click here.