NEW ADDITIONS AND THE QUALITY OF USED METAL

Reducing porosity rates will be affected by the amount of new metal used. It is obvious that the greater amount of fresh used, the lower the amount of oxide build up therefore a lower porosity rate. Reality is additions of 25-50% new metal for most users. When reusing old metal we suggest some of the following:

1. When using non de-oxidized alloys, use approximately 1/4 teaspoon of flux, borax or a 50/50 borax/borax acid mix. In silicon carbide crucibles use only boric acid. This will help gather the oxides formed, cover the molten metal to protect from absorption and increase fluidity of the metal. Be careful of flux being poured into melt!
    
2. When using de-oxidized alloys, use only enough flux to gather the oxides formed by the de-oxidizing agents. Usually add the flux by a pinch between your fingers.
    
3. When possible remelt old metal to remove investment powder and chemical compounds from devesting solutions. Flux melt as necessary and remove this residue flux containing oxide before pouring into shot.

NOTES: When adding fresh additions, it is advisable to maintain a consistent addition of fresh metal, such as 40% each day. 1OK gold will require a higher percentage of fresh metal, such as 50%, due to the faster oxidation rate (lower gold). We recommend mixing and shotting before casting. We recommend shotting old metal with new mix before casting. These steps allow for the most uniform consistency and control. When fluxing white gold, boric acid is preferable. Double the amount of flux for white gold.