Imagine two bronze ding vessels from the same period. One is unearthed in Anyang, Henan. The other in Changsha, Hunan.

Place them side by side, and you would hardly believe they came from the same era.

One is grey-green, calm, with a thin, tight patina and clear decoration. The other is mottled red and green, encrusted like armour, its original decoration almost buried.

This is not a difference in casting technique, nor in date. It is a difference in soil.

Bronze is an alloy of copper and tin. Buried in soil, it does not simply "oxidise". It enters a centuries-long chemical conversation with water, oxygen, acids, alkalis, and microorganisms in the soil.

The result of that conversation is patina.

Different soils give bronze different patinas.

Three environments, three patinas. Read the patina and you can roughly tell where it came from.

The north has little rainfall, alkaline soil, and good drainage. Buried there, bronze reacts slowly and the patina stays thin.

The most common colours are grey-green and blue-green — the classic northern bronze patina. It is often only a thin layer, clinging to the surface, with decoration still clearly visible.

The most prized northern patina is called black lacquer — a dense dark brown oxide layer, glossy as lacquer. It is not really "rust", but more like a skin the bronze has grown. Dealers say black lacquer is the finest of northern patinas.

There is also local turquoise green — fine, vivid, not garish, unique to northern pits.

Northern patina: thin, tight, bright.

The south has heavy rainfall, acidic soil, and a high water table. Buried there, bronze reacts quickly and the patina grows thick.

The most common colours are red rust and green rust — vivid, but loose, sometimes flaking at a touch.

The south also produces a special patina called mercury stain — a silvery grey sheen on the surface, as if coated in mercury. It is not real mercury, but a special oxide layer formed in long-term humid conditions.

Some southern bronzes, buried too long in too wet a place, are stained entirely deep brown or black-brown, with no decoration visible. These are often unpopular on the market, but a dedicated circle of collectors actively seeks them out — because those deep tones cannot be produced in the north.

Southern patina: thick, vivid, loose.

There is another case: bronze submerged in water for centuries.

Water holds less oxygen than soil, so the reaction is slower. This produces a special water-pit patina — grey-blue, relatively even, sometimes with a silvery sheen.

Water-pit bronzes often survive well, because low-oxygen conditions are the least corrosive to metal. But they have one problem: once removed from water, the patina can crack. They need careful conservation and cannot be kept too dry.

There is a saying in the trade: "Water pits produce masterpieces." It is not without reason — water-pit bronzes often preserve their form and decoration far better than southern-pit pieces.

Newcomers often ask: which patina is the most valuable?

That is the wrong question. Patina has no hierarchy — only authenticity.

Northern black lacquer is beautiful. Southern mercury stain is equally prized. Water-pit grey-blue has its own quiet appeal. Three patinas, three kinds of beauty.

What you should really guard against is fake patina — grown quickly with chemicals. Fake patina is flat in colour, single-layered, and has no "root". Real patina grows from the metal body; fake patina is painted on the surface.

Reading patina is ultimately about reading authenticity, not price.