Summary for argentium polishing stains Discussion
Argentium polishing stains are described as black marks that appear after casting and polishing, and the questioner says they cannot be removed by pickling or more polishing. Marc Banks Blacksmith of Elizabeth City, North Carolina identifies the problem as fire scale and says it can be removed with aggressive polishing. Alexandru Savu of SC SAVPROD SRL in Bucharest, Romania adds that a chemical cleaning solution and silver surface passivation can help keep the metal clean for a longer period. The thread therefore points to fire scale as the likely cause, with mechanical removal and chemical cleaning/passivation as the suggested remedies.
Q. When I cast Argentium after polishing a piece, black stains appears on the surface. I can not remove it pickling or polishing.
Where is the problem?
Adriana Cuellar
AJM – Santa Cruz, Bolivia
2006
A. This looks like fire scale. Most likely your flask was too hot or your melt was too hot or both.
Neil Bell
Albuquerque, New Mexico
 | That is fire scale, it can be removed with aggressive polishing. You can use a chemical solution for cleaning and Ag surface pasivation (to be maintain clean a long period!). |