Sizing an 18k and Platinum Ring

Editor’s Note: Working with platinum is unlike working with any other metal: It polishes differently, requires greater heat to work with, and is easily contaminated.

1. Measure out a 2.54 mm portion of the shank and, with a jeweler’s saw, cut away that portion of the metal. This will make the ring exactly one size smaller.

2. Using bow-closing pliers, gradually close the gap. By doing this evenly, you will keep intact the roundness of the ring; after soldering, the ring will need only a slight adjustment on the mandrel. For a tight fit, saw through the seam one more time once the gap has been closed.

3. To prevent the gold from oxidizing, firecoat the ring in a solution of boric acid and denatured alcohol. Then, using a torch and a soft flame; burn off the alcohol. This will evenly distribute the boric acid and make a protective glaze. Apply the yellow ochre to the gold section of the seam.

4. With a reducing flame, solder the platinum portion of the ring with 19k white weld solder. Be careful not to damage the gold sides. With the yellow ochre in place, the solder will stop before it overflows onto the gold. Pickle and clean the ring, then inspect the seam. If the seam is satisfactory, firecoat the ring again and apply flux to the gold areas, which will be soldered next.

5. Laying the ring on its sides, use 18k hard yellow to solder the remaining seams. The white solder will not flow again, since its melting temperature is higher than that of the gold solder. For this operation, I prefer to melt the 18k solder into a ball then pick it up and place it with a soldering pick,

6. The soldered seam,

7. Using a mandrel, check to make sure the ring still has the proper roundness,

8. After pickling and cleaning the ring, remove the excess

solder with a sandpaper stick-or a sponge file,

9. Use a silicon wheel to remove all traces of sizing, then round the ring on
the mandrel to ensure the ring size is correct.

10. Burnish the seam, using a tungsten burnisher that is brightly polished. This will blend the metal over the thin

solder area and make the seam invisible,

11. Lap the sides of the ring on a hard felt lap.

12. Gently polish the top of the ring with a bristle brush and a cotton buff, and the inside of the ring with a felt inside ring buff and a small felt buff.

13. The final two-color ring. The polishing compounds have been removed by steam or ultrasonic cleaning, and the original satin finish of the platinum has been
reapplied using a ScotchBrite pad or a fiberglass brush.

AJM, Feb. 2000
Jurgen J. Maerz | 800-759-9997 | (fax) 800-616-9997