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Cast Gold Springs; The next problem I was set was to provide a harder 9ct yellow gold for an earring clip post that would not bend when being opened and closed. The design was such that when the clip was opened there was the likelihood of the post bending due to the nature of the design, which was soldered on two small points, and the softening of the component taking place during soldering. I had observed whilst formulating 18ct palladium master alloy that the resultant metal was quite tough, so I used this to try a tough alloy for the post. It achieved the desired result regarding the toughness but unfortunately the colour was deficient as it had a distinctly pale colour due to the palladium content. Further work on this by the addition of copper only brought about a slight softening, not enough to preclude it from doing it's job, but with a brownish colour. I could not get the colour for the job required so didn't do any more with it for some time. Until a customer needed some necklet clasps cast, so I tried this alloy for the tongues with success, as the tongues can be cast and retain their tensile strength after casting, only needing their sprues removed and to be polished. This alloy has proved to be very useful for this purpose. The main drawback with it is it's limited colour range as the palladium necessarily keeps it pale. Starting with the master alloy I then used for 18ct Pd white gold consisting of copper, silver and zinc I added 12% Pd and 37.5% Au. We then replaced the Zn with additional copper to try to improve the colour for use with yellow gold. Then reduced the Pd to 5%.
We now use a master alloy Pd 8. 1, Cu 43.7, Ag 48.2. to which we add gold to make the appropriate carat rating required. We use this master alloy for 14ct and 18ct which, due to the increase in gold content, gives a much better yellow colour. The lower carat ratings are still not yellow but perform the task of retaining their tensile strength as cast. This series of alloys, which has evolved over a period of 20 years, can be wrought using normal jewellery fabrication methods. We make flat springs for Albert clips or draw wire to make springs for Cartier type clips. The fact that it will work harden means it will also loose some of its tension if being heated near red heat but it will still retain sufficient of it's tensile strength to maintain some of its spring advantage to be of benefit under certain situations. The main advantage of these alloys is their ability to retain an increased tensile strength when cast. Consequently cast jewellery components requiring spring tension action can be marked carat rated completely as the article contains all carat rated alloys. |
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