Behind a simple silver bar lies a precise metallurgical chain, from raw ore to the certified and sealed bar. Understanding how a bar is made also means better judging its quality, purity and resale value. Here are the main stages.
Where the silver in a bar comes from
Investment silver comes from two main sources: mined silver, extracted from mines (often as a by-product of lead, zinc or copper), and recycled silver, from jewellery, silverware, industrial or photographic waste. In both cases, the metal arrives at the refinery in an impure form: concentrated ore, doré (raw gold-silver alloy) or batches to be remelted.
The refiner’s first task is therefore to purify this metal to reach the investment fineness, generally 999 ‰ (99.9% fine silver).
Step 1: refining to 999
Refining separates silver from other metals. The reference process for silver is electrolysis, in particular the Moebius process: the impure metal serves as the anode, is immersed in a silver nitrate solution, and pure silver is deposited on a cathode as crystals of a purity above 999. You also find cupellation (oxidising fusion that removes lead) and the Balbach-Thum process.
At the end of refining, the silver is ready as granules or cathodes, at a guaranteed fineness. It is this purity that distinguishes an investment bar from a simple silver object. We cover this point in our article on silver refining.
Step 2: melting
The refined silver is then melted. Pure silver melts at 961.8 °C — a relatively low temperature for a precious metal, which makes it easy to shape. The molten metal is homogenised, its purity checked (often by spectrometry), then directed to shaping. Mastering this step determines the absence of bubbles and defects in the final bar. To go further, see the melting temperature of silver.
Step 3: casting or minting
This is where the two main families of bars diverge:
- The cast bar (cast bar): the molten metal is poured directly into a mould. As it cools, it takes on a shape with irregular contours, with a rough, matte look. It’s the most economical method, reserved mainly for large formats (1 kg and more), where the premium per gram is lowest.
- The minted bar (minted bar): the metal is first rolled into a strip of constant thickness, from which planchets are cut. Each planchet is then struck under a press between two dies, which imprint the design, weight, fineness and refiner’s logo, with clean, shiny surfaces.
We compare these two methods in detail in cast vs minted bar.
Step 4: marking, hallmarking and sealing
An investment bar carries a series of marks: the refiner’s logo, the weight, the fineness (999.0), a serial number for large formats, and where applicable a hallmark of guarantee. These elements make it possible to identify and authenticate the bar. This is the subject of our guide on the hallmarks of a silver bar.
Minted bars are finally sealed in a certified blister (CertiPAMP type at PAMP) that acts as a certificate and protects the surface. This seal is valuable: a bar kept in its original packaging is bought back without a “doubt discount”.
Who makes silver bars
Manufacturing is concentrated in the hands of a small number of accredited refiners, many of which appear on the LBMA Good Delivery List. The best known are Swiss (PAMP, Valcambi, Argor-Heraeus, Metalor), German (Heraeus, Geiger) or Anglo-Saxon (Royal Canadian Mint, Scottsdale Mint). We dedicate a page to each, starting with the PAMP silver bar.
Why it matters for the investor
Knowing about manufacturing sheds light on three concrete decisions:
- The format: a 1 kg cast bar costs less per gram than a small minted bar, because its manufacture is simpler.
- The brand: a recognised refiner guarantees purity and resale liquidity.
- Authenticity: seal, serial number and hallmarks are your best allies against counterfeits.
In summary
- A bar is born from refining (up to 999 ‰), melting (961.8 °C) then casting or minting.
- Cast = rough and economical (large formats); minted = clean and decorative (higher premium).
- Hallmarks, serial number and seal guarantee authenticity.
- Favour a recognised refiner (LBMA) for a smooth resale.
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This article is informational and does not constitute investment advice.