Inlaying precious metal like gold into a harder host metal is a process that has not changed for centuries. The techniques that the old masters used are exactly the same today and even the style of tools hasn’t changed. What has changed is the host metals have got a lot harder so the tools are also made of stronger materials.
Not to be confused with gold plating which is a micro thin layer of gold plated onto the surface of the metal, gold inlay is actually set and bonded into the metal and is quite thick. For the Taniwha watch 0.5mm 24 karat gold wire was used.
Step 1: The main outlines of the design are cut. The areas to be gold inlaid are then cut deeper (approximately 0.25mm) and relived. The outer edges are then undercut that gives a dovetail to the cavity. In bigger areas teeth are then cut into the surface to help grip the gold.
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Step 2: The gold wire is annealed then pressed into the cavity and then set by gently tapping it into place. At this stage this is to only hold the gold steady so that it doesn’t fall out.
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Step 3: The gold is then hammered in with a brass or bronze textured punch. This forces the gold down onto the teeth and spreads out along the bottom of the cavity filling the dovetails from step 1. The gold is now firmly in place.
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Step 3a: All the cavities are filled with the gold over the entire surface.
Step 4: The gold is then stoned down with a series of abrasive stones ranging from coarse to fine until it is flush with the surface. Wet and try grit paper can be used as the very last step but care must be taken not to round the edges.
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Step 4a: The entire surface is finished with the stones and abrasive paper.
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Step 5: All the main outlines are then recut including where the steel joins the gold.
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Step 6: The detail is then engraved into the design.
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Step 7: Extra lustre is given to the gold by burnishing very lightly. This is an optional step as depending on what is being engraved, as a high lustre is not always desirable.
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