Short answer
A fake Fifty Fathoms Grand Feu is a copy of a Blancpain dive watch whose dial carries grand feu enamel. Grand feu means glass powder melts in a kiln above 800 degrees Celsius. Copy dials sold as grand feu carry lacquer, resin, or a printed decal in most cases. Prices for first copy watches run from $80 to $400. A kiln-fired enamel dial at that price is not possible. Firing takes time, several passes, and rejects.
What grand feu enamel is
Grand feu is vitreous enamel. A metal dial blank gets a layer of powdered glass. The blank enters a kiln between 780 and 900 degrees Celsius. The powder melts, flows, and hardens. Each color needs its own pass and its own firing. A three-color dial fires three times or more. Reject rates run high. Bubbles, dust, and hairline cracks scrap a dial at any stage.
Enamel does not fade from UV light. It does chip. A drop on a hard floor can crack the surface. There is no repair short of refiring, and refiring risks the whole dial.
Genuine Fifty Fathoms reference points
Blancpain launched the Fifty Fathoms in 1953 for French combat swimmers. Fifty fathoms equals 91.44 metres. The case carries a rotating bezel for dive timing. Select Fifty Fathoms Bathyscaphe models use grand feu enamel dials. The calibre 1315 movement has three barrels and a 120-hour power reserve. Blancpain does not list dial material for every reference.
What copy dials use
- Lacquer over a stamped blank. Glossy. Shows orange peel at 10x.
- Printed dial with a clear coat. The print sits on top of the surface.
- Resin or epoxy dome. Soft under a fingernail.
- Two-layer enamel paint, air cured. Not fired.
- Most low-tier copies use a Miyota 8215 or a Seiko NH35 movement.
Checks with a 10x loupe
- Look at the dial edge. Fired enamel shows a rounded rim where it meets the metal.
- Search for air bubbles under the surface. Paint shows none.
- Check print depth. Enamel print sits flush or below the glaze. Decal print sits above it.
- Press a fingernail on the dial at an angle. Fired enamel is glass hard.
- Shine a light across the dial. Enamel reflects from the glaze layer. Paint reflects from the top coat.
Price bands
Copies at $80 to $150 use printed dials and mineral glass. Copies at $250 to $400 add a sapphire crystal, a screw-down crown, and better case finishing. No copy in this range uses a kiln-fired dial. A fired enamel dial from a specialist dial maker carries a cost in the hundreds of dollars on its own.
What is unknown
Dial material is not visible in photos. A seller can claim grand feu and ship paint. Confirming the material needs a lab test or a scratch test that damages the dial. Treat any listing that puts grand feu in the title as a style claim, not a material spec. Water resistance figures on copies are also unverified. A claim of 300 metres from an online seller has no test report behind it.