From granulate to bar: a walkthrough of the atelier floor

The refining floor at Kreta Ayer is small — deliberately so. A larger operation might process ten times the daily throughput. Ours is sized to keep every batch inside the eyeline of a single supervisor, which is the only way to enforce the standards that the assay card ends up claiming.

Refine

Batches start as high-purity granulate — small gold spheres that come to us pre-refined by a Good Delivery source and are re-refined on our floor to remove any surface contamination and to normalize purity to 999.9. The re-refining pass happens under an inert atmosphere in an induction crucible; contamination risk is highest at this stage, so we do not open the crucible for anything but a scheduled sampling pull.

Assay

Every melt is sampled and fire-assayed on the same floor. Fire assay is slow — a full cycle runs several hours — but it is the only method that resolves the last few parts per million with any confidence. An XRF check happens on the finished bar as a redundant surface reading. If the two disagree, the fire assay wins.

Cast or strike

For the cast bullion line — 10 g and above — molten metal is poured into custom graphite moulds, air-cooled, and trimmed. For the struck line — 1 g to 5 g — the metal is rolled into a strip and each card is pressed under die. Struck bars have a sharper edge and finer surface detail; cast bars carry the honest tool marks of the pour, which is part of why the market prices them as it does.

Stamp

Serial number, weight, purity, and mint mark are hallmarked in a single pass on a hydraulic press. The die is changed for every weight class, and the serial die advances mechanically after each strike — a partial safeguard against duplicated numbers. On the cast line, the same stamps are applied while the bar is still slightly warm; on the struck line, they are applied cold.

Finish

Bar faces are hand-finished. Struck bars get a mirror polish on the field with a matte inlay behind the hallmark; cast bars get a fine brushed face that lets the pour texture read through. This is the stage where a bench worker's judgment matters most — the surface has to look correct at arm's length and take a loupe cleanly.

Certify

Each finished piece is sealed into a tamper-evident card that carries the same serial as the bar, the melt reference, the assay result, and the date. The card is not decorative — its seal is the piece of paperwork that lets a downstream buyer trust the bar without re-assaying it. Break the seal and the piece becomes secondary-market material.