Brassing occurs when gold plating on bag hardware wears down to expose the underlying brass (or zinc alloy) base metal. It appears as a warm, slightly orange or copper tone on what should be gold hardware — most visibly on raised edges, corners of clasps, and points where the chain or strap contacts the hardware.
Some brassing is expected and accepted on most bags used for any period; it's a natural consequence of plating thickness limits. Very heavy brassing is considered significant wear and affects condition grade. Light brassing on turn-locks, chain links, and D-rings is normal for bags with 2+ years of use.
Brassing vs. Tarnish
Brassing is the physical removal of plating — it cannot be polished away. Tarnish is a surface oxidation of the plating itself, which can be gently polished off with a soft cloth. If light polishing restores the gold colour, it's tarnish; if the warm brass tone remains, it's brassing. Replating is the only solution for significant brassing, which is costly and changes the hardware's appearance slightly.