It is important to note that it is the composition of the alloy powder that is regulated - not the final filling. Stability criteria of the final product such as corrosion, emission of mercury vapor, etc. are not mentioned. The amount of mercury used to form the final amalgam mass is not regulated in this standard apart from demands regarding unmeasurable, subjective working qualities. ISO 1559 1st ed. One of the drawbacks identified in conventional amalgam is the instability of the metal in terms of corrosion leaving a black, tarnished surface.
Tin is however one of the most probable metals to form corrosion products.
As a consequence mercury is liberated when the gamma-two phase corrodes. Another drawback is the suspicion that conventional amalgams high creep values are responsible for an increased incidence of marginal fractures. Conventional amalgams are also subjected to the formation of droplets on the surface of severely deformed metal - a subject to be discussed later. Corrosion was identified as one of the major drawbacks of conventional amalgam. This corrosion mainly takes place in the gamma-two phase.