Over the millenia people have worked precious metals, they have evolved many different techniques for producing different finishes, structures and effects, however one of the oldest and still most important is casting. Although some aspects of the process have been streamlined with technology to improve speed and quality control, the basic process remains the same now as it did in the earliest metal casting processes, reckoned to date back around five or six thousand years BCE.
In this post, our master caster Andy Barnes takes us on a whirlwind tour of this ancient, and complex process…
The first step in the casting process is making a metal master, which might be produced in a variety of different ways, from hand-sculpting wax to making shapes and lettering in brass or other metals. It could even be taking a handmade, hand-chased piece of precious metal jewellery. However the master is made, it’s encased in liquid rubber, which solidifies to make a reusable mould for preparing wax masters for the casting process.
Making a rubber mould is quite a skill. It takes a lot of precise scalpel work to cut the mould to remove the original master, and make it reusable. One of the key skills is making little vents in the rubber so that when the liquid wax gets pumped in to make the wax master, the air can escape and no bubbles spoil the moulding.
“In the old days they used to cast using sand based moulds, which was hit and miss quality wise, it’s amazing the results they could get, though. The old sand-casters were very highly skilled master craftsmen.”
“It’s an organic process and never 100% reliable, but the slow kiln and high temperatures have greatly increased the reliability of mould making. The mould making takes much longer than the actual silver casting, but it’s essential for a consistently high quality finish.”
“We recycle as much silver as possible, but recycled silver loses some of its strength and durability. We have to balance our sustainable recycling programme with freshly alloyed silver to maintaining a workable finished product.”
“In the old days, we used a centrifuge to drive the liquid silver deep into the mould, and before that, silversmiths would heat the silver in a crucible, pour it into a sand mould and swing the red hot flask around their heads. Which produced unpredictable results, as well as being really dangerous.”
Most workshops can’t handle the sheer volume of business to keep a full time master caster employed, but feeding our busy workshop with fresh casts – and curating our huge library of moulds and masters we’ve accumulated over the last fifty years – keeps Andy busy all year round.
With Andy’s experience and expertise, we’re always pushing the art of casting forwards and incorporating cutting edge technology into the silversmith’s traditional craft. It’s the work of people like Andy that keeps Grant Macdonald’s workshops at the leading edge of precious metal craftsmanship.
“Part of my job is the same now as it was back in the 1600s, the other part is pushing the limits of what’s possible with the latest technology. I’m like that movie Back to the Future.”