There is clear harmony in the marriage of pure white platinum and the lush warmth of gold.  However, there are technical difficulties for the jeweler creating their bonds.  There are two major groups of bond types for metal work of all kinds; mechanical bonds and metallurgical bonds.

We are all familiar with many types of mechanical bonds.  We understand mechanical bonds quite readily because they are easy to see.  A few examples are screws, clasps, keys, and expansion fittings. There are many types of metallurgical bonds.  It helps a great deal to understand metallurgical bonds when alloys are perceived as solid solutions.  Alloys are mixes of pure metals dissolved into each other.  However, they do not mix completely into each other at all temperatures or concentrations.  Platinum and gold do not form many solid solutions at room temperature.

There are many types of metallurgical bonds.  Some examples are welds, soldering or brazing, puddling, and diffusion. There are two factors that might be a concern in the metallurgical bonding of platinum to gold.  The first, as previously mentioned, is that platinum and gold do not form many solid solutions at room temperature.  In general, they do not like to mix at all, like oil and water.  This makes for limited malleability and brittleness.

The second concern, mostly when brazing, is the coefficients of linear expansion.  Gold and platinum expand or contract at varied temperatures as all materials do, but at very different rates. 

There are major factors for achieving a good bond.  They are: Relief of all residual stresses; intimate contact of surfaces; and cleanliness of the interfaces.

It is wise to consider engineering factors when designing pieces that involve the bonding of platinum to gold.  If engineered properly, the mechanical bonding techniques of expansion fitting is very effective. The purity of platinum, its high melting point, and the non-corrosive nature of many of its alloys allows for special bonding techniques.  Gold can easily be puddled into recesses and onto unaffected platinum surfaces, so long as contaminants and oxides are kept from the gold.  Bi-metal casting is an excellent solution for combining gold and platinum.

Understanding the principles of bonding the alloys of platinum to gold alloys gives us many possibilities for experimentation.  The wonderful variations a jeweler can combine with the precious colors of noble platinum and gold are only limited by our imaginations.

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Bonding Platinum and Gold for Finished Jewelry
Steven Kretchmer
Steven Kretchmer Design

This is an abbreviated version of the original work. For full technical details, please consult the original paper.