A felt buff — also called a felt wheel — is a polishing wheel constructed from compressed wool felt, used in lapidary and jewellery workshops to impart a high lustre to gemstone surfaces and metal settings. It represents the final stage in the cutting and finishing sequence, removing the fine scratches left by earlier lapping and pre-polishing steps and bringing a faceted or cabochon stone to its finished optical brilliance. The felt buff is charged with a fine abrasive compound — most commonly cerium oxide, aluminium oxide, or diamond paste — chosen according to the hardness and chemical character of the material being polished.

Construction and Hardness

Felt buffs are manufactured by compressing and bonding wool fibres under heat and pressure into discs or cylinders of varying density. The degree of compression determines the wheel's hardness, which in turn governs its behaviour under polishing pressure. Softer felt wheels conform slightly to curved or irregular surfaces, making them useful for cabochons and carved pieces; harder wheels maintain a flatter contact face and are preferred for flat laps and the polished facets of faceted stones. Wheels are available in diameters ranging from a few centimetres for use on flexible-shaft machines and pendant drills up to larger discs mounted on dedicated polishing motors or combination units.

Polishing Compounds Used

The choice of polishing compound is determined by the Mohs hardness and chemical composition of the material being worked:

• Cerium oxide — the standard compound for quartz-group stones, glass, and many silicates. It acts partly through a mild chemical-mechanical interaction with silica-bearing surfaces, producing an exceptionally smooth finish.
• Aluminium oxide (alumina) — a versatile abrasive suitable for a broad range of gem materials, including softer stones where cerium oxide may be too reactive or insufficiently abrasive.
• Diamond paste — used for hard, refractory materials such as corundum (sapphire and ruby), chrysoberyl, and spinel, where softer compounds lack the hardness to remove residual scratches efficiently. Diamond paste is graded in micron sizes; grades of 0.5 µm to 3 µm are typical for final polishing stages.
• Chromium oxide — occasionally employed for certain silicates and for some metal surfaces, though its use has declined in favour of cerium oxide and diamond compounds.

Use in the Polishing Sequence

In standard lapidary practice, a felt buff is employed only after the stone has passed through progressively finer abrasive grits on a lapping wheel or grinding disc. Introducing the felt buff too early — before fine scratches from coarser grits have been fully removed — will result in a polish that appears bright under direct light but reveals sub-surface damage under oblique illumination or magnification. The wheel is charged by applying a small quantity of compound directly to the rotating surface; excess compound is removed by briefly running the wheel dry. Periodic re-charging maintains cutting efficiency, as the compound gradually depletes and the felt fibres become glazed.

Maintenance

Felt buffs require routine cleaning to prevent contamination between different compounds and to remove embedded stone particles that can cause scratching. A stiff brush or a piece of coarse abrasive held lightly against the rotating wheel will open the fibres and dislodge debris. Wheels used with diamond paste must be kept strictly separate from those used with oxide compounds, as even trace contamination can introduce scratches incompatible with the final grit size being employed. With proper care, a quality felt buff will provide extended service before the fibres wear to the point where replacement is necessary.

In the Workshop

The felt buff is standard equipment in both amateur and professional lapidary workshops, as well as in jewellery bench settings where metal polishing is required alongside stone finishing. Its combination of controlled firmness, compatibility with a wide range of polishing compounds, and ease of mounting on common workshop machinery makes it one of the most versatile and enduring tools in the lapidary's inventory.