Controls and quality demands in the jewellery investment casting process

The investment casting process, extensively used for the production of jewels, is made up of different phases that, for their intrinsic typology, are deeply influenced by many chemical, physical as well as metallurgical factors. Even though investment casting has been used for decades, it is absolutely not properly optimised, also in consequence of the difficulty in deeply understanding, and therefore controlling, all the different phases of the process. It is therefore evident that different, and unfortunately many, kind of defects may appear in precious art-crafts. The identification of the defect nature represents a decisive step in order to determine its cause; the comprehension of such an aspect is, consequently, the first important action to prevent the defect reappearance and, then, for the optimisation of the entire process. The present paper presents a general overview of casting defects and quality demands in jewellery and takes into exam some possible "non conformities" that can arise in the production of jewels. The defective samples have been examined throughout metallographic observations together with the use of SEM coupled with EDS analysis.