Diamond spray is an aerosol or pump-bottle suspension of graded diamond powder in a volatile carrier solvent, applied to faceting laps and polishing surfaces to deposit a thin, uniform abrasive layer. It occupies the same functional role as diamond paste but delivers the abrasive in a format that promotes rapid, even coverage and minimal waste — qualities that make it particularly well suited to smooth, non-porous lap materials such as phenolic resin and ceramic, on which paste may bead, migrate, or fail to adhere consistently.

Abrasive Grades and Sequence

Diamond spray is manufactured in a range of micron grades corresponding to successive stages of the cutting and polishing sequence. Typical grades available from specialist lapidary suppliers include:

• 15 micron — coarse pre-polish; removes deeper scratches left by grinding laps
• 6 micron — intermediate pre-polish
• 3 micron — fine pre-polish; suitable as a final step on softer gem materials
• 1 micron — near-final polish on most gem species
• 0.25 micron — final polish, producing a high-lustre surface on hard stones such as corundum and topaz

The progression from coarser to finer grades follows the same logic as any abrasive sequence: each step must remove the scratch pattern introduced by the previous one before advancing. Because the carrier solvent evaporates quickly, the abrasive layer left on the lap is thin; this demands more frequent reapplication than paste but also reduces the risk of over-charging the lap surface, which can cause facet rounding on hard stones.

Lap Compatibility

The choice between diamond spray and diamond paste is largely governed by lap material. On phenolic laps — a dense, smooth polymer surface widely used for final polishing — spray distributes more evenly than the thicker paste formulation and is less prone to pooling at lap edges. Ceramic laps, valued for their dimensional stability and hardness, similarly benefit from the spray format. On softer or more textured lap materials, such as tin, lead-alloy, or wooden laps, paste tends to charge the surface more effectively and may be preferred. Some cutters use spray on a charged leather or felt lap for the final polishing pass on delicate or included stones, where a gentler action is desirable.

Application Technique

Correct application is straightforward but consequential. The lap should be clean and rotating at working speed before the spray is applied; a brief burst from a distance of roughly 15–20 centimetres deposits an even mist across the surface. Excess solvent evaporates within seconds, leaving the diamond particles distributed across the lap. Most practitioners apply a small amount of extender fluid — typically a light oil or water, depending on the lap type — to maintain the abrasive in a workable state during cutting. Reapplication is needed whenever the lap begins to run dry, which is audible as a change in the cutting sound and visible as a reduction in swarf production.

Suppliers and Availability

Diamond spray is produced by several specialist lapidary suppliers. In the North American market, Gearloose and USFG (United States Faceters Guild) affiliated suppliers are among the better-known sources, offering both aerosol cans and pump-bottle formats in the micron grades listed above. European and Australian lapidary suppliers carry comparable products under various house brands. Pricing reflects the cost of synthetic diamond powder, which is consistent across grades; the carrier and propellant formulation account for a relatively small proportion of the product cost.

Comparison with Diamond Paste

Diamond paste — the same abrasive suspended in a grease or oil-based carrier — remains the more widely used format for charged metal laps (copper, tin, and their alloys) and for bench polishing of cabochons. Paste charges the lap surface more deeply and persists longer between applications. Spray is generally preferred where a thin, controllable charge is needed, where the lap surface does not readily absorb a paste carrier, or where the cutter values the speed and cleanliness of aerosol application. The two formats are not interchangeable in all situations, and many experienced faceters maintain both in the workshop, selecting the appropriate format for each lap type in their sequence.