The Bloom is on the Gold

November 22nd, 2008 by James L. Sweaney, CGA, FGA. GG

We recently followed a thread on the Orchid forum about “bloomed” gold. We have a beautiful example of bloomed gold in our estate department, a great Art Nouveau ring set with a very nice precious coral cameo and diamonds.

Note the beautiful rich color of the 18K gold and the soft matte surface. Bloomed gold simulates the look of 24K gold.  Besides Art Nouveau, it’s often seen on the “Revival” pieces of the Late Victorian period where the look of ancient high karat gold is sought.

Early in my career as a goldsmith, I learned the basic technique of leaching out the copper on the surface of both silver and gold alloys using repeating heating and quenching of the metal into standard jeweler’s pickle (a warm, slightly acidic solution).  This technique is not too predictable and can create problems with the metal because of the repeated heatings.  Other techniques use acids, iodine, and various nasty chemicals including cyanides.  Later in my training, I studied with an elderly German goldsmith who showed me another way using potassium nitrate and other salts—much better results but toxic fumes required doing the technique outside or under a fume hood.  Different techniques all create subtly different looking surfaces—some actually recrystallise the surface of the gold alloy.

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