Glass-forming minerals are melted with small amounts of cobalt and nickel compounds, which help the coating grip steel. Quenched, the melt breaks into flakes called frit and milled to a fine powder.

Clean steel sheet is coated with the ground frit, often a ground coat first and a white cover coat on top. That steel underneath is also what lets magnets stick to the finished board.

The coated steel runs through a furnace hot enough to melt the glass powder into a continuous, glossy skin fused to the metal. The cooled sheet is rolled into large coils for shipping.

At the board factory, the coil is unrolled and cut to size, then glued to a core of fiberboard, hardboard or particleboard with hot glue. Steel rollers press out air pockets.

A sheet of foil or thin galvanized steel is glued across the back of the core. It keeps out moisture that would otherwise swell the wood fibers and warp the board.

Finished panels are stacked on top of one another so their weight keeps steady pressure on the fresh glue. Once it cures, the panels are trimmed square.

Extruded aluminum trim is cut to length and slipped over the edges, with corner keys or brackets joining the pieces. A marker tray goes on the bottom before packing.