A diamond paste syringe is a small, sealed applicator — typically holding between one and ten grams of compound — pre-filled with oil-based diamond polishing paste and used to dispense controlled quantities of abrasive onto faceting laps, cabbing wheels, or polishing surfaces. By confining the paste within a syringe barrel, the format minimises contamination between grit sizes, a critical concern in fine lapidary work where even a trace of coarser abrasive introduced onto a finishing lap can scratch an otherwise polished surface.

Composition and construction

The paste itself consists of micron-graded synthetic diamond powder suspended in an oil carrier — most commonly a petroleum-based or light synthetic oil — chosen for its ability to hold the abrasive particles in uniform suspension without drying out during use. Grit designations follow the mesh or micron convention standard in lapidary supply: common grades range from approximately 3,000 mesh (roughly 6 microns) through 14,000, 50,000, and finer, with the highest grades used for final pre-polish and polish stages on hard gem materials such as corundum, spinel, and chrysoberyl. The syringe body is typically polypropylene, with a fine-gauge tip that allows the user to deposit a small bead of paste — often no more than a millimetre or two in diameter — directly onto the lap surface or onto a fingertip for transfer.

Use in faceting and cabbing

In faceting practice, diamond paste syringes are most commonly employed on metal laps (copper, tin, or typemetal alloys) and on composite ceramic or phenolic laps where the paste is charged into the surface rather than applied as a slurry. The syringe format is particularly valued when working through a sequence of progressively finer grits: each grade is stored in its own labelled syringe, and the lap — or a dedicated lap for each grade — is charged afresh without risk of cross-contamination from a shared container. Cabbing applications follow similar logic, with paste applied to leather, felt, or canvas polishing wheels for the final stages of dome finishing.

Economy of use is a practical advantage. Because diamond powder at fine micron grades is costly, the ability to dispense a precise, small quantity reduces waste. A single gram of 50,000-mesh paste, used judiciously, can polish a considerable number of faceted stones before exhaustion.

Suppliers and availability

Diamond paste syringes are produced and distributed by several specialist lapidary suppliers. Crystalite Corporation, a long-established manufacturer of diamond lapidary products, offers a range of graded paste syringes widely used in both amateur and professional workshops. United States Faceting Supply (USFG) similarly stocks graded syringes as part of broader polishing compound ranges. Syringes are typically sold individually by grade or in sets spanning a sequence of grits, allowing a lapidary to build a complete polishing progression from a single purchase.

Practical notes

Storage is straightforward: syringes should be kept capped and stored horizontally or tip-upward to prevent the oil carrier from separating or migrating. Contamination discipline — never allowing a syringe tip to contact a lap charged with a coarser grade, and wiping the tip before recapping — is the single most important handling practice. When a lap is to be charged with paste for the first time, a small amount is dispensed and spread with a fingertip or a clean wooden stick across the working surface, then the lap is run briefly before the stone is applied.