The macrography of ferrous metals, which has made it possible for these metals to study judiciously the processes of rolling, forging, stamping, casting, has so far not been applied with the same success to light alloys, precisely because the difficulty of obtaining the desired crystallographic appearance.

Patience and long research have enabled S. N. C. M. to develop an appropriate reagent with which the macrographies of the light metals needed for the above studies can be more easily obtained.

The study of forging and die-casting of light alloys becomes possible, because the macrographies thus made make it possible to study and apply the most judicious processes for the good execution of the parts.

The first photograph shows a piston that has not been processed by the indicated process. The study of the texture of the metal is therefore very difficult.

The following photograph shows a piston section where the metal appears in an almost amorphous state, without crystallisation, which makes it brittle.

The last photograph shows another piston obtained with a corrected matrix, in order to facilitate the flow of the metal without destroying the crystallization.