nigrescent

In addition, non-coated paper in high-humidity environment of sulfide, chemical pulp and fill applicatron dottle out acid melted, making of gold and silver monlchamus nigrescent who lose their luster.

此外，否涂料在矮湿度境况下，化学硫化物以及增添料洋磕酸矾土感化，也会使上金、银不朱发黑而获得光华度。