Telling Lost-Wax from Mould Casting

The Gap Is the Whole Story

Both methods produce a hollow bronze, and from the outside the two can look much alike. The difference between them is what held the hollow open while the metal went in — and that difference leaves marks.

In piece-mould casting, the outer mould and the inner core are two separate rigid pieces, and nothing about them keeps a distance. Left alone, they would simply meet. So the caster sets small metal pieces between them — spacers, at intervals, holding the core off the mould at exactly the wall thickness wanted. The Shanghai Museum's account of the technique gives them their own name: 芯撑, core supports.

Lost-wax casting has no such problem to solve. The wall is the wax. A model is built in wax at the thickness the finished wall should be, and the wax is melted out before the bronze is poured. Nothing had to be propped apart, because the space the bronze would fill was occupied by wax, and then by nothing.

So the two methods differ in a way a finished piece can still show. One of them needed props inside the wall. The other did not.

One more distinction is worth keeping separate from this one. Casting a vessel in a single pour and casting it in parts that are joined afterwards — 浑铸 and 分铸 — is a different question from which kind of mould was used. Either method can be poured in one go, and either can be built up from separately cast pieces. A seam on a bronze does not by itself tell you which of those happened. It tells you where something closed.

Where the Seams Show

A piece-mould is built in sections, and the joins between the sections leave their print on the casting. It is built that way because a rigid mould cannot be lifted off a shape that curves back on itself: to come off, the mould has to come apart. The mould is not used raw, either. The clay is shaped, dried, decorated and baked into a ceramic mould before any metal goes near it, which is what lets it take the heat of the pour. Most of the print it leaves is taken off afterwards: once the mould is broken away, the surface is ground and polished.

But polishing is done by hand, and a hand tool does not reach everywhere. On a surface crowded with ornament, it cannot get in between the raised lines without flattening them, so the seams survive there. On the base of a vessel, which is generally left plain and left unpolished, there is nothing to flatten and no reason to try. That is where the lines are easiest to find, and it is where to look first.

What the Supports Left Behind

A core support does not come out. It is metal, sitting in the space the bronze will fill, and it becomes part of the wall. Where it stood, it leaves a mark — 芯撑孔, a core-support hole.

This is the trace that belongs to piece-mould work. It is there because two rigid parts had to be held apart, and it is the one sign on a finished piece that exists for no other reason. What a core-support hole looks like on a particular vessel, and where it sits, depends on where the caster placed the supports, so no description can settle it in advance. The name is the thing to carry: 芯撑孔.

Reading the Traces

Put the three together and you have a way of looking at a bronze that does not need a laboratory. Seams, where the surface would not let them be polished away. Supports, left inside the wall. And on the other side of the line, the shapes a mould cannot be taken off: ornament so dense that pulling a section away would tear it, undercuts that curve back on themselves, and openwork with holes clear through the wall.

The method is old in China. The Shanghai Museum dates the use of lost-wax casting to the Spring and Autumn period, and the vessels it identifies as lost-wax work are consistently the ones carrying detail of that kind. Two of its examples are Spring and Autumn pieces — the ding known as 王子午鼎, and a gui decorated with openwork thorn patterns — both described there as objects that "should have been made by the lost-wax method."

What none of this is, is a test. There is no measurement here, no reagent, no certificate. It is a way of looking — at the base, at the ornament, at the places where a support once sat — and it tells you how a piece was made. It does not tell you what a piece is worth.

The bronze we carry is cast by the lost-wax method. The pieces are on our bronze replica page; how we describe what we sell is on our craft quality page.