Improved Puchtler's Congo red method for demonstrating amyloid

This paper describes a modification of Puchtler's alkaline Congo red method for demonstrating amyloid in human tissues. Special emphasis is given to the stability of the new staining solution, which has much greater stability than the one reported by Puchtler. This was accomplished by reducing the amount of sodium chloride and alcohol in the solution. The method is less time consuming than Puchtler's method because we found it unnecessary to pretreat tissue with alkaline sodium chloride in alcohol. Tissue sections are stained with a modified Weigert iron hematoxylin and placed into the alkaline Congo red solution for 20 min. They are then dehydrated rapidly in alcohol, cleared in xylene, and mounted with synthetic resin. Staining results obtained with this method are consistent and reliable.