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Metal Impregnation

Although staining with dyes is the most common way to make tissue structures identifiable microscopically, it is not the only way this may be done. Depositing metals onto or into structures is also very common. Silver is the metal most commonly employed, although gold, iron and copper have also been used. In spite of being a standard practice, it is still not completely understood in some respects. Learn more about metal impregnation from the resources below.

Silver Impregnation

Differing silver impregnations depend on differing processes, and some of these still appear to be somewhat arbitrary, while others can be almost fully understood. To illustrate, the precipitation of silver onto aldehydes by reduction from a methenamine silver solution (Gomori’s or Jones’ methods) is fairly easy to comprehend, but the impregnation of the various cells and their processes in brain is still largely a mystery. Learn more from the resources below.

Non-Silver Impregnation

Silver is the most common metal used for impregnation of tissue structures, but it is by no means the only one. Although it is relatively uncommon, gold can also be used for materials such as amyloid or the demonstration of astrocytes with Cajal’s gold sublimate (gold and mercuric chloride). Learn more from our detailed guide below.


Protocols for Metal Impregnation

Find step-by-step instructions for silver and non-silver impregnation methods.

View Protocols >


  1. Drury, R A, and Wallington, E A, (1967).
    Carleton’s histological technique., Ed. 5., p. 110.
    Oxford University Press, London, England.
  2. Wallington, E A,, (1965),
    The explosive properties of ammoniacal-silver solutions.,
    J Med Lab Technol, v 22, page 220-3.