What is Casting Grain?
Purified samples of precious metals that come in small granules. See “Grain” for the unit of measurement. Casting grains are used to create exact amounts of precious metal in metal alloys. Smelted non-precious metals grains are called master alloys.
Some casting grains can come with the master alloys already mixed in to maintain stability, but most jewelers or wholesalers prefer their grains to be pure so they can determine the final alloy percentage themselves.
Casting grains are available in a variety of karats, colors, and sizes. The color variation is due to the composition of the alloyed metals which also ultimately determines the relative strength of the grains. When master alloys and casting grains are combined they create precious metal alloys that can be evaluated for specific characteristics. These characteristics including the following:
- Scratch resistance
- Tarnish resistance
- Color
- Metal pliability
Gains are created through the process of casting. In casting, hot liquid metal is poured through a hollow instrument into a mold that contains a negative impression of the desired design. Finally, both the metal and mold are cooled, which allows for the separation of the newly solidified casted metal from the mold.
To create the granulation of the metal for casting grain, hot liquid metal is introduced directly into the water causing the metal to bead into the circular shape known as a grain. This process is often performed in a protected atmosphere to ensure final quality. The protected atmosphere prevents the introduction of oxygen during the metals’ most vulnerable stage. The introduction of oxygen while the metal is still molten could result in imperfections in the final product.
In most large modern grain casting operations, chemical analysis, and casting tests are completed on samples of the grains before they are made available for sale to the public.
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