Modern K2S Rapid Blackening Recipe
硫化钾快速乌银成色配方
并非所有「乌银效果」都需熔合真乌银：硫化钾（K2S）1–3% 水溶液 40–60 ℃ 浸 30 s–3 min，可令铜/银面生成硫化铜黑膜，视觉效果与镶嵌乌银接近、成本百分之一。配方分级：1% 浅灰、2% 深灰、3% 丝绒黑（超过 3% 膜层疏松脱落）。浸后流水冲净、氨水中和 30 s、微晶蜡封护。沟槽内颜色更深天然形成浮雕感——这是「假乌银」在批量饰品上的主流路线。
Most "niello look" today is chemical: soak copper/silver in 1–3% K2S solution at 40–60 °C for 30 s–3 min to grow a copper-sulfide black film—1% gray, 2% dark gray, 3% velvet black (above 3% it turns loose and flakes). Rinse, neutralize 30 s in ammonia, seal with microcrystalline wax. Grooves take a deeper tone naturally, faking raised relief—at 1% of fused-niello cost, this is the mainstream route for production jewelry. ---