Issue 13
Starring Silver
An average day. The alarm clock wakes you, and you switch on the light. You take a shower, heat water for coffee. You drive to work, take the lift to your office, switch on your computer. Just a typical workday, but it wouldn't be possible without silver.
You use silver every time, you turn on a light or run water out of a tap. Silver alloys help your tray of ice cubes freeze and your towels warm on a rack. A coating of silver turns a piece of glass into a mirror. At the flick of a switch, it helps ice melt from the rear windscreen in your car. When you travel, it is present in nearly any form of transport you choose.
Silver is the best conductor of electricity and best reflector of light and is second only to gold in workability. Its antiseptic properties ha' been known since ancient times when a silver lining was used to coat containers to keep drinking water potable. It alloys well with other metals, giving it hundreds of uses in brazes and solders.
At Thessco's twelve-acre site in Sheffield, if it has to do with silver, they probably either manufacture it or supply someone who does. Their products range from the decorative to the practical. They manufacture bars approved for London Good Delivery, coin blanks, hollowware and flatware, a well a gamut of products used by the chemical and electrical industries: anode, sheet, strip, wire, tape, tubing, casting powder, crystal, and brazing alloys.
Thessco's involvement with precious metals as The Sheffield Smelting Company dates back over 200 year. Today its refining, melting and raw material production form part of the Solpro Group, which was formed in 1967 by Mr Paul Tear.
From Croesus to the Bundesbank
In the museum at the Bank of England is a tiny disc made of a natural gold/silver alloy, known as electrum. One of the first coins ever minted, it was produced in Lydia, a part of Asia Minor, during the 7th century BC. King Croesus, who ruled Lydia from 564 to 560 BC, established the first government mint.
Though today's methods allow for a bit more precision and speed, the' basic process hasn't changed all that much. Back then, a disc was cast, placed on an anvil and covered with a die, then hit with a hammer to imprint an image onto the disc. Every year, Thessco stamps out many millions of thin discs whose destinations are mints around the world. Blanks of 999 silver can be used in circulation, but are a bit soft. Most coins used in circulation - such as a 10 DMK piece - have copper added for durability.
Planes , Trains and Automobiles
The word brazing dates back to the Middle Ages when the process for joining together plates of armour using brass powder or wire became known as 'bra5sing' and later brazing. "The Master from the Worshipful Company of Armourers and Braziers showed us an armoured glove from the 1600s with articulated fingers, all brazed together," said Paul Tear. "It was an amazingly sophisticated piece of work."
Unlike welding, the advantages of soldering and brazing become clear when joining two different metals with two dissimilar melting points.
Otherwise, when the two metals are heated, that with the lower melting point would dissolve into a molten pool of spreading liquid, while the second metal remained solid. But a third metal - the solder or braze - melts at a much lower temperature and sticks onto both parent metals to form a bond. Because silver alloys easily with so many other metals, it is an ideal choice to create brazes and solders, with a wide range of melting points and applications.
Thessco regularly manufactures 250 different alloys, of which about 100 are brazing alloys with countless applications. They are invaluable to the home appliance industry, to hydraulics and pneumatics, and heating and ventilating. The strength enables them to withstand the contraction and expansion caused by shifting temperatures. They can fill any sized space to create a solid joint.
"Silver brazing alloys are available for both thick and thin joints," explains James Tear, the second generation to the founder of the Sol pro Group. 'Thin braze. flow like water into the tiniest cracks and crevices to form a tight seal. But imagine trying to fill a wide gap with water - it would spill out all over the floor. So, when joining together a wide gap, you use a stodgy braze, one with Good consistency of treacle or molasses, to fill the gap. 'The result is a smooth, attractive and above all strong joint.
In one application or another, silver alloys are used in virtually every form of transport - bicycles, trains, buses, trucks, automobiles, bicycles and ships. And ice skates. "The skaters of the world are gliding on blades attached with bits of silver brazing alloy – and it is the strength of those bits that allow them to jump six feet in the air and land on an edge, "Paul tear points out.
What Silver Hath Wrought
When Samuel Morse typed out " What God hath wrought" on the first telegraph in 1832, it was silver that formed the contacts. As an unparalleled conductor of electricity, its applications naturally grew along with the industry.
Thessco manufactures strips, tapes and wires for electrical products such as contacts and fuses. Their wires start out as 4-inch thick billets but can be drawn down to about 30 microns - roughly one third the thickness of a hair. ln one unusual application, this fine wire is knitted into a gauze, which is then used in specialist seawater batteries for torpedoes and the like.
The silver used in a fuse must be very pure, in order to ensure that the fuse dependably carries current - and equally dependably blows as soon as it is overloaded. Because silver conducts electricity so well, only tiny bits are needed. The fine wire consistently carries the correct amount of current without breaking - but must burn through as soon as the current is overloaded.
When making a switch, a small silver contact is brazed onto a large copper block. While copper isn't as good a conductor of electricity, it's there for economic reasons. "You try to achieve a balance between size and expense when designing a switch," says James Tear. "Expense is an overriding factor. You could use only silver, but then people would want to steal switches for their silver content."
Electrical contacts are used for switching on anything from a bedside light to a power station. Thessco's customers produce various grades of switches. The largest might switch on the power to an entire hospital. The next size clown might isolate one floor. The next, one wing. The smallest would switch on a monitor for a single patient.
The art of silver
Of all the uses of silver, ornamental silver has perhaps the longest history: silver accessories have been found in tombs dating from 4000 BC. It is second only to gold in terms of workability and is more practical: many pieces would become prohibitively expensive if fashioned out of gold.
A Solpro Group division manufactures cutlery (any item with a cutting edge), flatware (knives, forks and spoons) and hollowware (basically any large piece, from a candelabra to a bowl, or a teapot to a tray). Thanks to the use of computers, the time needed to manufacture each piece has been greatly reduced.
Some patterns used by Solpro date to the earliest designs ever produced, while others can be brand new, individually created for a special customer. From a drawing of a single piece, they can produce the tools and dies needed to manufacture a full set of flatware. Then each piece will be cut, stamped, polished and if desired, enamelled and gold-plated.