Pre-finishing Platinum

Quality Assurance Benchmarks highlight workmanship of semi-finished and finished jewellery. Learn best practices for pre-finishing platinum jewellery.

Perspective view of a platinum ring with a halo setting, featuring a split shank set with diamonds

The last and most important step in any platinum repair, alteration or manufacturing process is finishing. Finishing includes pre-finishing, polishing and buffing.

Pre-finishing – After making an alteration such as a sizing change, it is necessary to burnish and pre-finish the worked area to remove irregularities from the surface. In this case, pre-finishing involves using files and/or abrasives in progressive steps prior to polishing.

Polishing – Using a variety of wheels and compounds progressively to smooth and brighten a platinum piece

Buffing – Using a variety of wheels and compounds progressively to obtain a superior bright white high platinum lustre

Perspective view of a platinum solitaire, featuring a split shank set with diamonds

The last and most important step in any platinum repair, alteration or manufacturing process is finishing. Finishing includes pre-finishing, polishing and buffing.

Pre-finishing – After making an alteration such as a sizing change, it is necessary to pre-finish the worked area. In this case, prefinishing involves using files and/or abrasives in progressive steps prior to polishing.

Polishing – Using a variety of wheels and compounds progressively to smooth and brighten a platinum piece

Buffing – Using a variety of wheels and compounds progressively to obtain a superior bright white high platinum lustre

Pre-finishing: Quality Assurance Benchmarking

Little or no metal should be removed during the three steps of pre-finishing platinum jewellery. If removing a small amount of metal is necessary, take the following precautions.

Close-up view of a jeweler using a rotary burnisher to prefinish the inside of a platinum ring

Start with the appropriate grade of file or abrasive. For example, in a sizing-up process, the dimensions of the added piece will be larger than the ring dimensions. Begin pre-finishing by filing to make the new piece closer in size. Do not remove metal from the ring.

After filing the added piece to match the shank dimensions, begin with the smoothest grade of abrasive to remove the file marks. Grades range from 220 (coarse) to 8000 (ultra-fine).

Platinum rings must be rounded prior to pre-finishing

Side view of a platinum princess-cut solitaire

Rounding requires light hammering of the ring on a mandrel, using a rawhide or nylon hammer. When rounding this ring, be careful not to distort the geometry or dimensions.

Side view of a platinum band featuring three flush-set diamonds

Attempting to pre-finish a ring that’s out of round will cause deformation and/or reduction of overall dimensions. Dimensional retention of proper shank depth and width is important for long-term wear.

Maintain Design Elements and Engineering Detail

Perspective view of a platinum ring with diamonds set in the shank

Pre-finishing should not remove design elements or engineering details such as the prong shapes below the side stones. Selecting the right tools for pre-finishing is essential for success.

Most of the pre-finishing for this ring is completed after the stones have been set. If not careful, excessive pre-finishing could reduce prong dimensions, which can make the stones more likely to fall out of their settings.

It’s important to carefully pre-finish and polish after setting the stones. This practice provides a better finished look.

Three illustrations featuring platinum, three-prong solitaire earrings

Note that the sides of the prongs have flat surfaces that intersect with a rounded gallery wire. Careless pre-finishing can cause deformation of the parts and a mismatch between the earrings.

Most of the pre-finishing for these earrings, such as the sides of the prongs, is completed before setting the stones. Excessive pre-finishing can increase the likelihood of stone loss.

Pre-finishing and polishing prior to setting provides easier long-term cleaning of the debris that collects during normal wear.

Pre-finish all small, hard-to-access areas

Two close-up views of platinum solitaire settings, featuring negative space and other design details

Pre-finish beneath the stones and inside all junctions, holes, recesses and any negative space in the design

Remove the cast surface, tool marks and any oxidation left behind from soldering (platinum cobalt alloys only)

Maintain Dimensions

Close-up views highlighting the height and depth dimensions of a platinum band, including an illustration depicting clock locations (12:00, 3:00, 6:00 and 9:00)

Record the critical dimensions of pieces being repaired or altered before starting work. If sizing, for example, record the width and depth dimensions at the 6:00 location where the joint will occur. This information may be important for discussions after work has been completed.

Record the width at the 6:00 location where the joint will occur

Also record the depth at the 6:00 location where the joint will occur

Shape Retention: Maintain Flat Areas

Close-up view of a platinum solitaire with the center stone removed

Observe the piece carefully before you begin, and select tools and techniques to keep the integrity of the original form. Flat areas need to remain flat, and curved, shaped and rounded areas must be true to their original form.

Be careful to retain all shaping. On the featured ring, the prongs are flat. They must remain flat as the bezel edges are pre-finished.

Close-up view of the ring being prefinished

Use a variety of pre-finishing tools that fit the contours of the jewellery

Pre-finishing: Tools and Techniques

Initial Pre-finishing Steps

Close-up view of a jeweler cleaning a platinum solitaire in preparation for prefinishing

Clean and then inspect the piece, documenting any damage. Next, burnish the piece, tightening stones if necessary. Begin pre-finishing. To avoid contamination, keep all filing and pre-finishing tools dedicated to platinum.

Abrasive Wheels

These Foredom rubberised wheels contain ceramic abrasive material and are available in six grades. They range from coarse 120 grit (blue) to superfine 1500 grit (white).

These wheels are resilient, hold an edge and generate less heat

When pre-finishing platinum, start with the inner surfaces. As wheels wear and become smaller, they are ideal for use inside a ring.

Identify grades of abrasives on the tool’s shaft. Proper placement allows for quick location of, and access to, the tool needed.

Cross-contamination is one of the biggest problems encountered during the platinum finishing process. So always remove the debris from the piece that has been left behind from coarser grades of materials before moving on to finer grades.

Close-up view of a jeweler using an abrasive wheel to prefinish a platinum ring that incorporates flat wires as part of the design

Finer abrasive wheels (1000 grit and higher) leave a semi-polished surface on platinum, making the polishing steps more efficient

This wheel has a flat surface that is ideal for pre-finishing the flat wires of the ring design

Close-up view of a jeweler using a shaping stone to shape an abrasive wheel

For rounded edges or tight sharp areas, abrasive wheels can be shaped using a shaping stone. Here, a knife-edge is being formed onto a wheel that had a flat bottom.

Abrasive Bands

3M Flexible Diamond bands and discs are made from a two-ply polyester backing film evenly coated with diamond-filled dots. They are available in a wide variety of abrasive grades, and can be used wet or dry for progressive smoothing.

Keep all abrasive tools labelled and organised for more efficient finishing

Abrasive Papers and Film

Six varieties of platinum micro-finishing film

Micro-finishing film contains electrostatically and consistently oriented micron-graded mineral particles, making progressive pre-finishing efficient

These materials are fast-cutting, uniform and resin-bonded, and are available plain or with an adhesive polyester film backing

Here, the film is wrapped around flat sticks. It can be used in a variety of pre-finishing applications.

Micro-finishing film is also available in strips and other shapes. It can be custom-fitted for tools that have various applications. This is important for retaining design details and uniformity.

For organisation and efficiency, label the abrasives from coarse to fine. Use them only for platinum.