You transfer 100 grams of fine gold to your workshop. Six weeks later they deliver a ring weighing 12 grams. Your account is debited 9.9 grams, and 90.1 remain.
All three numbers are correct. But if you do not know where the 9.9 comes from, you can neither check it, nor challenge it, nor predict it on the next order.
This article explains that calculation, step by step, with a single example we follow from beginning to end.
First, an obvious point that settles half the misunderstandings
Your 100 grams have not gone anywhere. They are on your account, at your workshop, and they stay there until you order something.
A jobbing workshop works on consignment: the metal remains your property at all times. It does not buy it, resell it or own it. It holds it, transforms it, hands you back a piece and deducts what that piece consumed.
So this is not an invoice, it is an account in the banking sense: credits, debits, a balance. The trade calls it a weight account.
Two immediate consequences.
The account is kept in grams, never in euros. The gold price may double between your transfer and the delivery; it changes nothing about the number of grams the workshop owes you.
And it only moves on delivery. While the ring is in production your balance does not change: the metal is at the workshop, and it is still yours.
Why the account is kept in fine gold
Your ring weighs 12 grams. But 12 grams of what?
18 carat gold is not pure gold. It contains 750 parts per thousand of fine gold, the rest being copper, silver or palladium depending on the colour. So a 12 gram ring in 18 carat contains:
12 × 0.750 = 9 grams of fine gold.
The remaining 3 grams are the alloy, and the alloy cost you nothing: the caster adds it.
That is why a weight account is always kept in fine gold, at 24 carats. It is the only unit that does not move.
Take two 12 gram rings, one in yellow 18K, the other in white 18K. Same weight on the scale, different alloys, different colours. In fine gold they both come to 9 grams. On an account kept in 18K they would happen to match; the day you produce a piece in 14 or 9 carat, the account starts lying and nobody notices.
Remember: the carat describes the piece, fine gold counts the metal.
The debit calculation, in three lines
Back to the ring. It leaves the workshop, it is weighed, it ships to you. Here is what happens to your account.
Line 1: the net weight. The finished piece is weighed and anything that is not metal is removed. A plain 12 gram ring stays at 12 grams. A ring set with diamonds weighs more than its metal, and we come to that below.
Line 2: conversion to fine gold. 12 grams of 18 carat make 9 grams of fine gold.
Line 3: the flat-rate loss. The workshop adds a flat percentage, most often in the region of 10%.
9 × 1.10 = 9.9 grams of fine gold debited.
Your statement then looks like this.
| Movement | Fine gold | Balance |
|---|---|---|
| Initial transfer | + 100.000 g | 100.000 g |
| Delivery, 12 g 18K ring | − 9.000 g | 91.000 g |
| Flat-rate loss 10% | − 0.900 g | 90.100 g |
Three lines, three numbers you can verify. You can redo the arithmetic by hand, and that is precisely the point: a weight account you cannot recompute yourself is worthless.
If your workshop shows the same movement in alloy grams, it will write 13.2 grams instead of 9.9. It is the same metal: 12 × 1.10 = 13.2 grams of 18 carat, which contain 13.2 × 0.750 = 9.9 grams of fine gold. Both notations are correct, but you have to know which one you are reading, otherwise the 3.3 gram difference looks like an error.
What the 10% flat rate actually pays for
This flat rate is not a disguised margin. It pays for metal that genuinely disappeared between the ingot and your ring, and that cannot be recovered.
- The saw kerf. A cast piece arrives attached to a tree by feed rods. They have to be cut, and every pass of the saw turns a little gold into dust.
- Filings from deburring. Casting marks are filed off. Some of it is caught in the trays, some is not.
- Polishing sludge. This is the heaviest item. Polishing tears off metal that ends up in the felts, the brushes, the compounds. Workshops have these residues processed, but the yield is never a hundred percent.
- Setting residue. The setter removes material to seat each stone.
A figure for scale: on an ordinary piece, these real losses often sit between 5 and 8%. So a 10% flat rate covers them with a margin, and that is deliberate. The margin absorbs the unfavourable cases, one of which we detail below.
What you do not see, and why that is normal
Behind your single debit line, the workshop manages two flows that are none of your concern. It is useful to know they exist, if only so you do not go looking for them.
The caster's loss
When the workshop sends metal to its caster, the caster takes a loss, generally between 2 and 4%. An important detail: that loss applies to the total cast weight, meaning the piece and the feed rods.
That loss is paid by the workshop, not by you. It never appears on your statement.
The feed rods
On a 12 gram ring, the complete tree often weighs 40 or 50 grams. Those rods are cut, sorted, then sent back for recycling, and their metal returns to the workshop's pool, not to your account.
That is the mechanism that makes the flat rate viable. The workshop charges 10% on the finished piece, pays the caster's loss on a much larger weight, and recovers the rods. Under normal conditions the balance tips slightly in its favour, and that is the price of the service.
When the balance breaks
A small piece on a large rod, a heavily pierced design, a run of prototypes: a flat rate computed on 12 grams no longer covers the real loss taken on 50. The workshop loses money on that piece.
Those cases are settled individually, between people who talk to each other. But they can only be settled if they are seen, and they are only seen if the total cast weight is traced, not just the delivered weight. If your workshop asks for an adjustment on a specific piece, it is not cheating you: ask for the tree weight, and you will know.
The stone trap, the costliest error
If your ring goes out for setting, it comes back heavier. Stones have a weight, and that weight is not metal.
Take the same 12 gram ring, set with 0.80 carat of diamonds. One carat is 0.20 gram, so the stones weigh 0.16 gram. The piece coming back from the setter weighs 12.16 grams.
If the workshop debits on that gross weighing:
12.16 × 0.750 × 1.10 = 10.032 grams of fine gold.
Instead of 9.9. You have been charged 0.132 gram of fine gold that is in fact diamond. On one ring that is small. On a full pavé, across an entire collection, it runs into tens of grams a year.
The weight that counts is always the net weight: gross minus stones. And that stone weight must come from the bill of materials, not from an eyeball estimate.
The same rule applies to a chain mounted on a pendant: if the chain came from you, it must not be debited a second time.
The flat rate is not a universal constant
Ten percent is the most common order of magnitude in French workshops, not a rule. The rate is negotiated, and it is legitimately negotiated at two levels.
By client, according to volume and type of production. A regular customer ordering simple pieces does not get the same rate as an occasional customer ordering complex ones.
By product, when a model has unusual geometry. A heavily pierced piece loses more in polishing, and that can justify its own rate.
What must be written down is the rate and its base: on fine weight or alloy weight, on the plain piece or the set piece. A rate without a base means nothing, and that is where most disagreements come from.
What comes into your account
The debit side is the complicated subject. The credit side less so, but it takes four forms that are not handled the same way.
Account-to-account transfer. The most common and the most misunderstood: nothing moves physically. Brands and workshops deposit their metal with a bailee, a kind of metal bank, and transfer grams from one account to another. The metal never leaves the vaults.
Component shipments. Chain by the metre, clasps, findings. These are objects, they arrive by carrier, they are weighed on arrival.
Direct supplier delivery. You buy in your own name but have the goods delivered to the workshop. The parcel never passes through you. This case has a regulatory consequence we cover just below.
Recovered metal. After-sales returns, bought-back jewellery, offcuts from old collections. This metal is rarely at the required standard: it must be refined before it can be credited in fine gold, and refining has a cost that is deducted from what is credited.
One principle common to all four: the weight is what counts. As soon as metal leaves your stock, your position must be deducted, whether or not the shipment is attached to an identified inventory lot. Attaching to a lot is a traceability convenience, never a condition.
The precious metals register: what goes in, what does not
Manufacturers and dealers in precious metals keep a register of their purchases, sales, receipts and deliveries. The obligation does not depend on who owns the metal: it covers everyone holding such materials in the course of their profession. So your workshop must record your gold, even though it does not own it.
Be careful with the legal basis, a great deal of online content is out of date. Article 537 of the French General Tax Code, long cited as the reference, was repealed by ordinance no. 2023-1210 of 20 December 2023, effective 1 July 2025. The text now in force is article L. 834-6 of the French Commercial Code, supplemented by articles 56 J quaterdecies to 56 J octodecies of annex IV to the General Tax Code.
Three practical rules that often surprise people.
The virtual is not recorded, the physical is. An account-to-account transfer at the bailee produces no entry: nothing came in, nothing went out. But when the raw pieces come back from the caster, that is a physical receipt of precious material: it is recorded, at the weighed weight, with the delivery note as evidence.
Wax is not a precious material. Sending a wax tree to the caster is not recorded. This is a frequent confusion.
On direct supplier delivery, the counterparty is you, not the supplier. The parcel never passed through your premises, but the metal does enter your consigned stock at the manufacturer. It is your name that appears in their register.
The six causes of drift
A weight account never drifts all at once. It drifts through small repeated omissions. The six that keep coming back, in order of frequency:
- A casting return not entered. The parcel arrived, it was opened, nobody entered the weighing the same day.
- A rod shipped without a trace. It goes off for recycling, it comes back as a credit two months later, and nobody knows which shipment it belongs to.
- A component received without weighing. A chain, a clasp, entered into stock without going past the scale.
- Stone weight not deducted. Covered above. It is the costliest single error.
- A failed piece not traced. The metal still exists, it went to scrap gold, but nothing says so.
- Invisible metal in transit. This one is not an error: it is a normal state. But if it appears nowhere, it looks like a discrepancy.
Closing, the only moment of truth
None of the above is worth anything unless it is reconciled regularly. A serious close, every two weeks, fits in one equation:
Balance at the bailee + metal in transit + physical inventory at the workshop = sum of client accounts + the workshop's own account.
If it balances, all is well. If not, the gap is investigated before the next close, never after. A threshold that works in practice: beyond one gram, you go looking.
One gram looks trivial. Repeated every two weeks across ten clients, it makes 260 grams a year, and nobody will ever know whose they were.
Four questions to ask before your first order
If you are opening a weight account with a new workshop, these four answers prevent most disputes.
- What is the loss rate, and on what base? On fine weight or alloy weight, on the plain piece or the set piece.
- Is stone weight deducted, and where does it come from? From the bill of materials or from an estimate.
- How often can I get a statement? And in what form, exportable or not.
- What happens on a failed piece? Who bears the loss, depending on the cause.
A serious workshop answers all four without hesitating. It is a rather good test.
Liink keeps this account on both sides of the relationship. Every consigned gram is expressed in fine gold, every delivery produces the three lines of the calculation, and the precious metals register fills from physical receipts. The brand and the workshop read the same statement, at the same moment, and nobody has to remember anything.