A brass dop is a short, precision-machined cylindrical rod of brass used in gem faceting as the primary means of holding a rough or partially cut stone against the lap. The stone is temporarily secured to one end of the dop with dop wax or a modern thermoplastic adhesive, while the opposite end is gripped by the collet of a faceting machine's quill. Brass dops are manufactured in a standardised range of diameters — typically from around 4 mm to 25 mm or more — allowing the faceter to select a dop whose face closely matches the girdle diameter of the stone being cut, thereby maximising support and minimising the risk of the stone shifting under pressure.

Material Properties and Why Brass Is Preferred

Brass — an alloy of copper and zinc — is the material of choice for dop sticks in professional and serious amateur faceting for several well-established reasons. Its moderate thermal conductivity allows the dop to be heated evenly and predictably with an alcohol lamp or dedicated dop heater, softening the wax to a workable consistency without the risk of overheating that might damage heat-sensitive stones. Once cooled, brass retains its shape without warping, a limitation that can affect aluminium dops over repeated heating cycles. Brass is also readily machinable, meaning that dop faces can be turned to precise diameters and flat or cupped profiles with consistent tolerances — a requirement when the dop must seat accurately in a faceting machine's collet. Its density gives the dop a reassuring rigidity during cutting, reducing vibration transmitted to the stone.

Aluminium dops are lighter and less expensive, but they are more prone to dimensional distortion with repeated thermal cycling and offer slightly less rigidity. For this reason, brass remains the benchmark material among professional faceters and is standard equipment supplied with most quality faceting machines.

Forms and Profiles

Brass dops are available in several end profiles to suit different faceting tasks:

• Flat-face dops — the most common form, used for attaching the table facet of a stone during pavilion cutting, or for any situation where a flat wax bed is appropriate.
• Cone or V-dops — machined with a conical recess that cradles the pavilion of a partially cut stone during crown cutting, providing a mechanical as well as adhesive grip.
• Notched or grooved dops — used in transfer dopping to align the stone precisely when flipping it from pavilion to crown orientation.

The shank diameter of a brass dop must correspond exactly to the collet size of the faceting machine in use; the most widely adopted standard in modern machines is a 6.35 mm (¼ inch) shank, though older or specialist machines may differ.

Use in Dopping and Transfer

The process of attaching a stone to a brass dop — known as dopping — begins by warming the dop, applying a small quantity of dop wax to the face, and pressing the pre-warmed stone into the softened wax. Correct centring and alignment at this stage are critical, as any tilt introduced here will propagate through every subsequent facet. Once the wax has cooled and hardened, the dop is inserted into the faceting machine and cutting proceeds.

When the pavilion is complete and the stone must be transferred to cut the crown, a second brass dop — typically a cone dop sized to receive the finished pavilion — is warmed and aligned against the first using a transfer jig. The wax on the new dop bonds to the pavilion, and after cooling, the original dop is carefully released by gentle rewarming. The precision of this transfer operation depends heavily on the dimensional consistency of the brass dops and the accuracy of the transfer jig, underscoring why machined brass is preferred over softer or less stable materials.

Care and Maintenance

Brass dops require little maintenance beyond cleaning residual wax from the face after each use — a task accomplished with gentle heat and a cloth, or with a solvent such as acetone for stubborn residue. The shank should be kept free of burrs or corrosion to ensure a clean fit in the collet. With reasonable care, a set of brass dops will last indefinitely, making them a sound long-term investment for any serious faceting workshop.