BLACKENING UNITED’S DEOXIDIZED STERLING SILVER ALLOYS: May be accomplished using “Silver Black” from Griffith Distributors @ 303 442 8284 or “Black Max” from Rio Grande @ 505 839 3000. It is helpful to use iron or steel hooks for the dipping process with these chemicals as it helps speed the reaction. The normal “Liver of Sulfur” solutions do not blacken United’s deoxidized Sterling Silver alloys well. Some of our customers have reported that a photographic chemical called “Rapid Selenium Toner” will blacken our deoxidized Sterling Silver Alloys.
REMOVE ALL INVESTMENT RESIDUE ON STERLING SILVER SCRAP BEING RE-MELTED. Any investment powder residue on scrap being re-melted will decompose at elevated temperatures releasing sulfur compounds into the melt. The sulfur compounds will combine with oxygen forming sulfur dioxide gas that is absorbed by the molten metal causing porosity in the silver castings.
Sterling silver may be hardened by the following methods:
For hard rolled sheet, plate and wire, solution anneal at 1200 degrees F. for 20 minutes and quench in water or pickle solution. The articles are then placed in a pre-heated oven at 300 degrees C / 575 degrees F. for 1 hour and allow to air cool. For investment cast articles, just the lower temperature heat treatment is required. If the articles are soldered after heat treatment, the heat treatment must be repeated to restore hardness.
ACID GOLD PLATING SOLUTIONS SHOULD BE USED on United’s deoxidized Sterling Silver Alloys. The usual cyanide gold plating solutions do not bond well to our deoxidized Sterling Silver Alloys unless various pre-treatments or sub-plating processes are used.
ADVISE YOUR CUSTOMERS NOT TO WEAR STERLING SILVER JEWELRY IN THE SWIMMING POOL. The high Chlorine and/or Bromine contents used in swimming pools can accelerate the tarnishing of Sterling Silver jewelry.
REMOVING THE BLACK TARNISH FROM STERLING SILVER may be accomplished by placing a double layer of aluminum foil in the bottom of a dish pan, adding hot water and 2 – 3 heaping tablespoons of baking soda. Place the black tarnished item in the dish pan to soak in contact with the aluminum foil for a few minutes and the tarnish will come off. Rinse the items well and buff with soft polishing cloth to restore luster.