Metal refining
5 steps from ore to pure
The gold used by the Mint is refined in five major stages:
1. Pre-melt
Doré bars in purities ranging from 5% to 95% are melted in a furnace. Dip samples are taken from the molten gold to determine its purity.
2. Chlorination
Chlorine gas is injected into the molten metal mix. All metals but gold float to the surface to form a slag of molten chloride. The resulting 995 fine gold is poured into an anode mould.
3. Degolding
Soda ash is added to the molten chloride slag recovered from chlorination. The reaction causes gold particles to collect in a silver-gold alloy 'button' that settles at the bottom of the crucible.
4. Electrolysis
This process brings gold to 9999 purity. The gold anode is placed in a bath containing a solution of hydrochloric acid and gold chloride. The anode is then subjected to an electric current. The anode dissolves, and the dissolved gold plates onto a titanium cathode. Impurities (mostly silver) fall to the bottom of the cell or form soluble chlorides.
5. Final pour
9999 fine gold is cast into bars of various sizes or turned into granulation gold.
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Design
Beautiful coins begin with beautiful designs. We take pains to choose coin designs that resonate with Canadians. They must be meaningful, memorable ? and reproducible on metal.
Selecting a theme
While the obverse side of all Canadian coins bears the effigy of the reigning monarch, the reverse side displays a distinctive design with a thoroughly researched theme. The theme usually reflects an event, place or milestone of national interest.
We sometimes conduct public opinion polls to help determine which themes Canadians find most interesting or evocative.
Choosing a design
Once a theme has been chosen, the Mint commissions artists to submit designs. We provide them with background information, design concepts, creative and technical guidelines, coin specifications, and previous examples.
While we traditionally enlist the services of well-known Canadian artists, many of the most distinctive designs in our collections are the work of the Mint's own staff of talented designers and engravers.
The art of coin design
Coin designs must have artistic merit, be reproducible on metal blanks, and accurately depict the subject matter.
For example, the initial design for the 2-dollar polar bear coin was scrutinized by a zoologist to make sure the bear's anatomical details were correct. The Mint's production experts then suggested enhancements to make the design stand out on the round, metal surface of a coin, such as concentrating details in the centre of the coin, not around the rim, and the use of a strong contour line to distinguish the bear from the background.
Who decides which designs are chosen for Canadian coins?
Ideas for new coin designs come from contests, research and the general public. Recommendations are sent to the Government of Canada, which makes the final decision for all coin designs.
Numismatic coins are approved by the Minister and circulation coins by the Governor in Council.
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Hand crafting
The art of the detail
The Ottawa Mint specializes in the production of hand-crafted commemorative coins and medals. In contrast to the high-volume turnover of the Winnipeg facility, the Ottawa operation produces an average of just 8,000 collector coins per eight-hour shift. Each piece is treated as an individual work of art.
5 steps from precious metal to a precious collector coin
1. Concasting
2. Rolling
3. Preparing for striking
4. Striking
5. Engraving
1. Concasting
A numismatic coin begins its life. Silver is melted down into large bars, then these newly-poured bars are chopped using a cutter into smaller pieces. These pieces slowly move out of the furnace and through a series of cooling boxes before proceeding to the saw, which cuts the bars into pieces approximately two feet long. Next, the planer removes a thin layer of silver in order to expose the shiny, unoxidized interior.
2. Rolling
Bars are thinned out by passing through two steel rollers at the roughing mill to produce 4 mm thick gold bars and 8 mm thick silver bars.
Annealing
Silver is annealed by heating in a furnace. Gold bars do not require heating as they are much softer and more pliable. Over the course of 6-7 hours, the temperature of the annealing furnace reaches a white-hot 700°C. Annealed silver bars are then rolled a second time by the finishing mill.
Finishing
Bars are then thinned out a second time in the finishing mill. Skilled workers measure each of the rolled metal sheets produced by the finishing mill to ensure that the desired dimensions are reached with total precision.
Blanking
The blanking press then cuts blanks (coins without any image) from the rolled metal sheets. These blanks are punched out with a special die the size of a coin, powered by 40 tons of pressure per square inch. The leftover material, called scissel, is sent back to the refinery for recycling.
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3. Preparing for striking
A blank must undergo many steps before a design is committed to its surface. Each stage is necessary to ensure longevity, precision and appearance.
Rimming
This machine removes the rough edge left by the blanking press and adds a raised rim prior to striking. Doing this ensures that the detail from the die will transfer flawlessly when the coin is struck. A rim can add 10 to 15 years to a coin's life.
Blanks are burnished by tumbling for up to six hours with stainless steel beads of various sizes that wash and polish their surface. Each tumbler is used for a specific alloy to prevent cross-contamination. Blanks are then spread out evenly and thoroughly hand-dried with towels to prevent scratching.
Degreasing
After burnishing and prior to striking, the blanks go through a final inspection and cleaning. Degreasing is done using the Finsonic process: blanks are dipped in alcohol and hot water (50-60°C) for about 15 minutes. Imperfect blanks are sent back to the concasting room and re-melted.
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4. Striking
Coins produced at the Ottawa Mint are unique works of art. The painstaking care involved in making numismatic coins represents a commitment to the highest standards of minting. Blanks are transformed into coins in either the automatic press room or the manual press room, where images are added to both sides.
Automatic striking
Automatic presses are mainly used to strike coins made of non-precious metals (nickel, copper, etc.), but occasionally strike more precious pieces such as gold bullion and investment coins. In an automatic machine, the dies will strike an average of 2,000-5,000 hits before they are changed.
Manual striking
Manual presses are used to strike blanks made of precious metals (gold, silver, platinum) to create collector or numismatic coins. Most proof coins are struck twice or even three times. Tool steel dies, placed inside each press, are used to imprint the desired design on the coin's surface.
5. Engraving
The Mint's engravers execute the meticulous designs that grace finished coins. Each design is carefully translated from paper to die, and quality controlled every step of the way.
Etching and copying
The original design is etched onto discs much larger than the coin to retain as much detail as possible. A plaster copy of the coin design is transferred onto a rubber disc, producing a positive image. It is then transferred onto an epoxy resin disc to produce a negative impression of the original design.
Reducing
A reducing machine works like a key cutter by following the contours of the original epoxy disc to engrave a smaller scale version onto a brass plate.
Die making
Dies used to strike coins are copied from the reduced original design. A second reducing machine takes the brass plate and shrinks all of the information onto a steel die called the matrix, technically the original die. This can take up to 48 hours, after which the matrix is copied to produce the master punch, a process called hobbing.
The master punch is then hobbed onto another blank die to produce working dies (or proof dies), which are used in presses to make coins. Proof dies are capable of striking coins and leaving a frosted image on top of a mirror-like background.
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Mass production
Speed meets precision
The Winnipeg Mint is Canada's high-volume coin production powerhouse. Here, the industry's most technologically advanced processes and equipment produce up to 15 million plated coins each day for Canadian and foreign circulation. Our adherence to the highest manufacturing standards is what makes the Royal Canadian Mint a valued provider of coins to countries worldwide.
How circulation coins are produced
Circulation coins are minted using the world's most advanced minting techniques, patented technologies and rigorous statistical sampling to ensure the highest quality standards.
Producing blanks
Large coiled strips of core steel are fed into a high capacity punch press, which can produce over 13,000 blanks per minute!
Refining the raw materials
The core metal blanks are deburred to remove any rough edges, then rimmed (a raising and slight rounding of the edges), annealed (heated to better receive the strike), and cleaned.
Enhanced security
Electroplating is the practice by which steel coin blanks are coated with nickel and copper plate for protection. The Mint's exclusive patented multi-ply plating technique is the world's only multi-ply layer process that can match the electromagnetic signature of any traditional alloy coin – an enormous security advantage for the coin-operated vending industry.
Exacting standards
After plating, the coins are dried, polished and then sorted by a state-of-the-art inspection camera which examines up to 180,000 blanks per hour for blistering, colour variations and surface defects. Now the coins are ready for striking by a high-speed coining press. Once the coins have been rolled and wrapped, they are shipped to the Mint's coin pool sites across the country for distribution to financial institutions.
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