5µ paraffin sections of neutral buffered formalin fixed tissue are suitable.
Other fixatives are likely to be satisfactory. Cryostat sections usually show brighter metachromasia.
Unmounted frozen sections may also be floated in each solution and mounted on a slide just before coverslipping.
Bring sections to water via xylene and ethanol, except for cryostat and frozen sections.
Place into methyl green solution for 1-5 minutes. (frozen sections stain more rapidly than paraffin sections).
Rinse well with water.
If necessary, differentiate in dilute acetic acid until amyloid is red and contrasts well with the tissue.
Rinse well with tap water.
Drain all water from the slide until just damp and blot dry.
Flood with triethylphosphate, then with xylene, and coverslip using a resinous medium.
Amyloid – purple-red
Background – Green
Nuclei – Green
The methyl green must not be washed with chloroform. Doing so will remove any crystal violet and it is the crystal violet which actually stains the amyloid metachromatically.
Ethyl green is often supplied under the name methyl green. This works as well as true methyl green, but must also not be washed to remove any crystal violet.
If the metachromatic staining is poor due to a low crystal violet content, a little crystal violet may be added to the methyl green solution.
Reference Drury, R A, and Wallington, E A, (1967). Carleton's histological technique., Ed. 4, p. 222.
Oxford University Press, London, England.