Root Causes of Loose Wire & Gray Niello
嵌线松动与乌银发灰的根因分析
标签：根因分析, 松动, 乌银发灰, 熔剂残留, 锁槽缺陷
嵌线松动的常见根因：槽底比槽口宽（应口窄底宽形成倒扣）、银丝未退火（冷硬丝回弹）、敲击顺序错误——正确做法从槽两端向中间逐步压实，先轻后重；槽内有氧化皮或抛光膏残留也直接削弱咬合。乌银发灰不黑多因：表面覆盖硼砂玻璃状熔剂残膜（稀氨水或 10% 柠檬酸温洗可除）、抛光局部过热致硫化银部分分解析出游离银、酸洗过度留下亚表层。判定后处理：残膜清洗后重新抛光；过热件需重新低温熔合一次（低于初熔 20℃）恢复致密黑色。
Loose wire traces to four roots: grooves wider at the mouth than the base (the reverse of the required undercut), unannealed springy wire, wrong hammering order—work ends toward center, light to heavy—or oxide and polishing compound trapped in the groove. Gray rather than black niello comes from a glassy borax flux film (removed with dilute ammonia or warm 10% citric acid), overheating during polish partially decomposing the sulfide, or over-pickling. Fixes: clean and repolish filmed surfaces; overheated areas refuse once at 20℃ below original melting to restore dense black.