Quality control
Bronze casting defects: what to accept
Every hand-cast bronze piece carries marks. Which ones are normal, which ones are rejects, and how to write an acceptance rule into your order.
Every piece of bronze that leaves our floor in Dong Quy carries marks. Some are how the metal behaves and belong on a finished piece. Some are faults, and we remake those at our cost before the crate closes. The line between them is a written rule, not taste: a height difference of 1–3 cm on a large piece is normal, over 5 cm is a defect. Here is the rest of that list, so it goes into your order rather than an argument later.
Why does hand-cast bronze never come out identical?
Each piece is cast in a hand-dressed mould, then cut from its gate, chased and patinated by hand. Two moulds from one master are never identical to the tenth of a millimetre, and metal shrinks as it cools in proportion to thickness. Our altar pieces run about 5 mm in the wall, 8 mm where the piece carries load — a foot, a handle, a lid knob. A size 65 five-piece set weighs roughly 36 kg; two of them can differ by a few hundred grams and both be right. An acceptance rule demanding an exact match to a drawing is one no hand foundry passes.
Which surface marks are normal?
- Fine orange-peel texture on large flat faces. Polishing it out would thin the wall.
- Grinding marks where the pouring gate was cut off — on a base or inside a foot, dressed level, invisible in display position.
- Patina shifting in tone across one piece. A perfectly even colour is the signature of paint, not bronze.
- Height 1–3 cm off the nominal size on anything over half a metre.
Which faults are always rejects?
- A crack of any length, or a hole through the wall.
- More than 5 cm off the nominal size.
- Wall under about 5 mm, or under 8 mm at a foot, handle or joint.
- Engraved text closed up, or a Vietnamese diacritic that cannot be read.
- Two pieces of a set that will not stand level side by side, or a base that rocks.
| What you see | Normal or defect | What happens |
|---|---|---|
| Fine orange-peel texture on a flat surface | Normal | Left as cast; grinding it out thins the wall |
| Grinding marks where the gate was cut | Normal, on a base or inside a foot | Dressed flat, unseen in display position |
| Height 1–3 cm off nominal size | Normal | Shipped; measured heights go with the packing list |
| Height more than 5 cm off nominal size | Defect | Remade at our cost before shipment |
| Gas pinholes under about 1 mm, off the display face | Normal | Filled and dressed |
| Crack of any length, or a hole through the wall | Defect | Remade; never filled and sold |
| Patina uneven in tone across one piece | Normal | Shipped; a set is patinated in one batch |
| Engraved characters closed up, diacritic unreadable | Defect | Remade; text is proofed on photo first |
How many pieces should be checked in a lot?
For altar sets, every set: five pieces have to work together, so a sample check says nothing about whether the crane stands level beside the burner. For repeats of one small item in quantity, name the sample size in the order and what a failure in it means — sort the lot, or reject it.
We publish no AQL figure: quoting one we have not agreed with you would be a number invented for a web page. Put yours in the order and we will confirm it in writing or say it is not realistic for hand casting. Same honesty on certification — we hold no ISO or BSCI file. What carries the promise is the rule you and we sign, photographs at each stage, and the standard applied to the sets in our showrooms in Nam Dinh, Hanoi and Hai Phong.
Who pays to remake a rejected piece?
We do, for faults on the list above found before shipment — the whole point of catching them while the lot is on our floor. What a remake costs you is time: a new casting runs the same 21–30 day window unless we can add it to a batch already in progress. That is the argument for inspecting before the container is booked. Once a crate has travelled, the question becomes transit damage and is handled a different way: bronze damaged on arrival.
How do I write an acceptance rule the foundry will agree to?
Keep it to one page: nominal sizes and the tolerance you accept in centimetres; wall thickness at the load points; the automatic rejects; how many pieces are checked and by whom; who takes the acceptance photographs, and when. Send it with the enquiry, not after the deposit. We mark anything we cannot meet before the mould is dressed — the one moment when changing it costs nothing. For the dimensional side see tolerances in hand casting; for how the check is run, pre-shipment inspection; our own process is on quality control.
Questions buyers ask
Two sets of the same model are slightly different. Is that a defect?
No. Within 1–3 cm of height and a few hundred grams, that is hand casting. Sold as a matched pair they should still be patinated in one batch — worth asking for in the order.
Can I let small pinholes go?
Under about 1 mm, away from a face or lettering, yes: they are filled and dressed. Pinholes in a row, or anything you can get a fingernail into, go back.
Will the foundry remake a rejected piece free of charge?
Yes for faults on the reject list, found before shipment. No for a change of mind on size, finish or design after the mould is dressed — that is a new piece, and we say so plainly.
Can I reject a whole lot because of a few pieces?
Say so in advance and we will agree the threshold in writing. A lot rejected without a rule set before production is a dispute; with one it is arithmetic.
Who takes the acceptance photographs?
We do, before the crates close: each piece numbered, a tape measure in frame on tall pieces, the inside of the foot where the wall shows. To watch live, ask for a video call from the floor.
Send the acceptance rule with your enquiry. Tell us the models, sizes and quantities and we will mark what we can hold to, in writing, before anything is cast. Use the request a quote form or WhatsApp at +84 926 199 999; we answer within two working days.