Authentication by the study of the structure of the materials present in the object

Techniques allowing a magnification and a best resolution of the surface :

Metallography

a. Principle :

consists in cutting off a sample from the objects to authenticate, in polishing the metallic fragment after its coating with resin and in observing, with the help of a microscope equipped with an inverted objective, the structure and the composition of the alloy as well as the aspect and the possible deep penetration of the corrosion products

b. Applications :

objets made out of copper alloys (cf. bronze, brass) or even auriferous alloys

c. Advantages :

this type of examination allows :

• to reveal :

• the inner corrosion in old bronzes from which the external patina has been completely removed
• the false patinas obtained from paint or corrosion products taken from ancient objects
• the external patinas or internal deteriorations resulting from an accelerated corrosion induced by immersion in acid solutions

  Genuine object: presence of internal corrosion

  False object: homogenous structure, absence of in depth alteration

• to identify the method used for the assembling of parts which have been cast separately (cf. hard solder, tin-lead solder)
• to give precise details about the manufacture mode of metallic objects (cf. hammering)

Other techniques of magnification : stereoscopy - electron microscopy