Bronze or brass?
Is this bronze or brass, and how would I know?
You almost certainly cannot tell by looking. Once a patina is on, bronze and brass reach a similar range of colours and neither weight nor a photograph will separate them. The reliable method is documentary, not visual: require the metal to be named on the quotation and on the invoice, in words, before any money moves.
01 · The short version
The short version
A finished brass casting and a finished silicon bronze casting can look identical. Not similar. Identical, to most buyers, under most lighting.
That is not a failure of attention. It is what patina does. Patina is a chemical reaction on the surface of a copper alloy, and both metals accept a similar range of colours. Whatever difference exists in the raw metal is largely gone by the time the piece is finished.
So the question "is this bronze or brass" has no reliable visual answer, and the useful response is to stop trying to answer it by eye.
02 · The difference
What actually separates them
Both are copper alloys. That is the source of the confusion, and it is also the reason the difference is real.
| Bronze | Brass | |
|---|---|---|
| Copper alloyed with | Tin, or silicon in the case of silicon bronze | Zinc |
| Raw material cost | Higher | Lower |
| Behaviour in the mould | Different flow and different shrinkage | Different flow and different shrinkage |
| Colour after patina | Broad range | Broad range, overlapping heavily with bronze |
| Usually chosen for | Editions, permanent work | Decorative work, cost led projects |
The price gap between them is a metal price gap. It is not a margin choice made by an individual foundry, which is why it does not disappear when you find a cheaper supplier. If the metal price gap has disappeared from a quotation, something else in the quotation has changed instead.
03 · Four questions
The four questions that settle it
Ask any foundry, including this one, for all four in writing. A supplier who answers all four plainly is telling you exactly what you are buying, and the whole exercise costs nothing.
1. Which metal, named? Not "bronze finish", not "bronze colour", not "antique bronze", not "bronze effect". Those describe an appearance, and an appearance can be produced on almost anything. The answer you want is a metal: silicon bronze, or brass.
2. Solid cast metal, or a composite? Cold cast and bronze resin are resin with metal powder in them. They are a different product, they are legitimately cheaper, and they should be named. See is cold cast bronze real bronze.
3. Chemical patina, or paint? A patina is a reaction with the metal underneath. Paint is a layer sitting on top of it. They age completely differently and they are worth different money.
4. If the work is editioned, what happens to the mould when the edition closes? The answer determines whether your edition stays an edition. See who owns the mould.
04 · Cheaper quotes
When a quote comes back much cheaper
This is the situation that brings most people to this page: a lower quotation elsewhere, described in the same words, for what appears to be the same object.
It is worth working out what changed, because a lower price usually reflects something real. Any of these will move the number, and all of them are ordinary decisions rather than misconduct:
- a different metal
- a resin composite instead of solid cast metal
- a thinner wall, so less metal in the piece
- less chasing, so the joins and the casting texture are still faintly visible
- a painted finish instead of a chemical patina
- fewer stages done in one place, with the piece moving between workshops
None of that is a reason to distrust a supplier. It is a reason to compare like with like. When both quotations name the metal, name the finish and describe the same amount of finishing work, the comparison becomes honest and you can simply pick the better price.
05 · Where we stand
Where we stand
We do not describe a brass casting as bronze, including when a client asks us to. If a project is brass, the quotation says brass and the invoice says brass.
That is a standard rather than a complaint. It exists so a client can rely on what our documents say, and so a buyer who later resells the piece is not handing on a description they cannot support.
07 · Common questions
Common questions
How can I tell if a sculpture is bronze or brass?
Not by eye, in most cases. Both are copper alloys, both take a similar range of patinas, and a finished patina removes the colour difference that exists in the raw metal. The dependable method is to require the metal to be named in writing on the quotation and the invoice before paying.
Why is bronze more expensive than brass?
The raw metal costs more. Bronze is copper alloyed with tin or, for silicon bronze, with silicon. Brass is copper alloyed with zinc. The gap is in the material itself, so it persists no matter who does the casting.
I was quoted much less for bronze somewhere else. What does that mean?
It means one of a small number of things, and it is worth finding out which. It may be a different metal. It may be a resin composite rather than solid cast metal. It may be a thinner casting, or less chasing, or a painted finish rather than a chemical patina. Any of those can be legitimate at the right price, but they are not the same product.
Does weight tell me which metal it is?
No. The densities of common bronze and brass alloys are close enough that weight is not a usable test, and wall thickness varies more between castings than the alloys do.
What should I ask a foundry to put in writing?
Four things. The metal, named. Whether the piece is solid cast metal or a composite. Whether the finish is a chemical patina or paint. And, if the work is editioned, what happens to the mould when the edition closes.
Is brass a bad choice?
No. Brass is a legitimate material and the right answer for plenty of projects. The problem is never brass. The problem is paying a bronze price for it.
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