Sizing Down: Platinum Cobalt with no Diamonds in the Shank Using a Torch

Quality Assurance Benchmarks highlight workmanship for semi-finished or finished jewelry. Learn how to evaluate the quality of a platinum cobalt ring with no diamonds in the shank that was sized down using a torch.

Side view of a platinum solitaire with no diamonds set in the shank

Ring is round

No excess solder

Finger size is accurate

Sizing joint is not visible

No pits in the solder joint

Oxidation removed from all portions of the ring

Perspective view of a platinum 4-prong solitaire with no diamonds set in the shank

Sizing joint is not visible

No pits in the solder joint

Quality and hallmark stamps are visible

Shank’s shape and original dimensions maintained

There are no tool marks and the piece is brightly polished and finished

Potential Problems and Engineering Features

Avoiding Problems by Using Proper Torch and Soldering Techniques

Hold the platinum ring with tungsten carbide- or platinum-tipped tweezers. Place a few layers of tissue between the tweezers and the ring to prevent scratches.

Cover the center stone with firecoat solution. Wrap it with wet tissue to protect from the intense heat.

Use 1,700 platinum seamless repair solder. Preheat the inside of the ring, holding the torch below the joint. Position the torch so that the area just beyond the flame’s inner cone is at this location, then move the torch to a position above the joint, directly heating the joint and solder.

Use an intense oxidizing flame for soldering platinum cobalt

Pull the torch back as soon as the solder melts and flows into the joint. The flame must be intense, as the wet tissue and carbide-tipped tweezers act as a heat sink and pull heat away from the joint.

How-to Video

Sizing Down Platinum Cobalt with no Diamonds in the Shank Using a Torch

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Tool and Topic Related Info

Consumers often ask to have the removed piece returned to them. In this case, the removed piece has a weight of 0.3 pennyweights.

Close-up view showing a platinum band with a piece removed from the ring shank in preparation for sizing it down

The piece is too small to be of any value to a consumer. A retailer factors the value of the scrap into the price for the service. Allowing the consumer to keep the piece would considerably increase the cost.

The piece removed during size reduction weighed 0.3 pennyweights. Twenty pennyweights equal one troy ounce.

Approximately 2.2 millimeters = 1 size

The current platinum market price is $1,686.00 per ounce. Based on current pricing, the value of the small piece of scrap is approximately $25.00.