An alcohol lamp — also termed a spirit lamp — is a small, open-flame burner fuelled by denatured alcohol (typically ethanol or methanol) and used in the lapidary studio principally to melt shellac-based dopping wax when affixing rough or preformed gemstones to dop sticks prior to faceting or cabochon polishing. Its defining practical virtue is a clean, soot-free flame: unlike a candle or petroleum-fuelled burner, a correctly trimmed alcohol wick produces no carbonaceous residue that might contaminate the wax bond or discolour a pale stone.

Construction and use

The instrument is simple in construction: a small glass or metal reservoir holds the fuel, a cotton wick draws liquid upward by capillary action, and a metal collar or snuffer cap controls both flame height and extinguishment. Reservoir capacity is typically 30–100 ml, sufficient for an extended cutting session. The flame temperature is moderate — well below that of a gas torch — which is precisely the quality that makes it appropriate for dopping: shellac and standard dopping waxes soften and flow at roughly 65–90 °C, a range easily achieved and maintained over an alcohol flame without risk of overheating thermally sensitive stones such as opal, tanzanite, or certain treated rubies.

In practice, the lapidary holds the dop stick and stone assembly in the flame just long enough to soften the wax, seats the stone at the correct angle, and allows the assembly to cool undisturbed. The same lamp is used to warm a transfer jig when re-dopping a partially faceted stone to cut the opposite end — a procedure in which even heat distribution is critical to maintaining precise alignment.

Historical context

The alcohol lamp has been a standard fitting of the gem-cutting studio since at least the mid-nineteenth century, when the expansion of amateur and professional lapidary work in Europe and North America created demand for reliable, low-cost bench tools. John Sinkankas, whose Gem Cutting: A Lapidary's Manual remains a foundational reference in the field, describes the spirit lamp as the conventional heat source for dopping, noting its controllability and the absence of troublesome combustion by-products. The tool's longevity in a craft otherwise transformed by motorised laps, digital angle gauges, and synthetic abrasives speaks to the difficulty of improving upon its functional simplicity.

Practical considerations

• Fuel: Denatured alcohol (methylated spirits) is standard; isopropyl alcohol at high concentration is an acceptable substitute. Fuel purity affects flame cleanliness.
• Wick maintenance: A charred or frayed wick produces an uneven, sooty flame; regular trimming to a flat, clean edge is recommended.
• Ventilation: Alcohol vapour is flammable; the lamp should be used in a well-ventilated space away from volatile polishing compounds.
• Heat-sensitive stones: For opal, emerald with heavy fracture filling, or any stone suspected of having resin or oil treatment, the lapidary should minimise direct flame exposure and consider low-temperature wax formulations or two-part epoxy dopping systems instead.

Relation to dopping wax

The alcohol lamp is functionally inseparable from dopping wax: neither is useful without the other. Standard shellac-based wax is brittle at room temperature, providing a rigid mechanical grip on the stone during grinding and polishing, yet releases cleanly when reheated. The alcohol lamp's moderate, adjustable flame makes it the preferred means of achieving this thermal cycle repeatedly and safely across a working session. Some contemporary lapidaries have adopted small butane micro-torches or electric wax pots as alternatives, but the alcohol lamp remains widely used for its low cost, ease of refuelling, and the fine degree of manual control it affords.