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A Reproduction of the Royal Society's Cook Medal

 
In 2008, to mark the 30th birthday of the Captain Cook Birthplace Museum (1978) and the 280th anniversary of Cook's birth (1728) the museum issued a replica of one of the most important Cook commemorative medals.

Issued in 1784, the Captain Cook Medal was commissioned by the Royal Society, of which Cook was a Fellow, and produced in gold, silver and bronze [see Cook's Log, page 28, vol. 31, no. 3 (2008)]. A bronze example of the Medal had been recently acquired by the museum and, working in association with Westair Reproductions, a historical giftware manufacturer based in Birmingham, a replica of the gold and silver medals were produced. All three medals are now exhibited at the museum and a packaged silver issue is on sale to the public in the museum's shop at £4.99 each.

Here is an outline of the two-week process behind the reproduced medals.

The Master Mould

The master mould is normally made with vulcanized rubber but due to its value, in the case of the Captain Cook Medal, a special silicone mould was used. Silicone requires much lower heat and pressure than rubber in the vulcanization process, thus ensuring that no damage was caused to the original medal.

The process started with two round discs of un-vulcanized silicone. The discs were 30cm in diameter and 1.5cm thick. The original medal was placed on one side of the silicone disc and chalk was added to each half to stop them sticking together. Locators were then made in the bottom half of the disc to help the two halves align together, and a hole was cut in the centre of the top half of the mould for the metal to be poured through.

Click on any image below for a larger version
The Moulding  Frame
The Moulding Frame
The  Vulcanizer
The Vulcanizer
Once the two halves were placed together, the mould was inserted inside a hot moulding frame and then in-between two hot plates of a vulcanizer, where a small amount of pressure was applied.

The combination of heat and pressure "cured" the silicone and the now vulcanized mould was ready to be prepared for casting.

This final process involved cutting channels with a sharp knife through the silicone from the centre of the disc to the medal imprint, to allow the metal to flow, and from the bottom of the imprint to the outside of the disc, to allow air to be released when the mould was cast.

The finished mould was then ready for casting.

The Production  Mould
The Production Mould
The Casting  Machine
The Casting Machine
The Casting Process

Chalk was again added to the mould, this time to help the metal to flow through the channels and into all the cavities. The mould was then placed inside the casting machine between two metal plates and locked into place.

The casting machine spun under high pressure. Molten metal, heated to over 300 degrees centigrade, was poured down a funnel and distributed centrifugally through the mould. When the machine stopped, the mould was removed and opened to reveal the perfectly reproduced cast medal.

With the museum wishing to sell the reproduction medal in quantity, this process was repeated seven times to produce eight finished medals. These were then used to cast an eight-medal production mould in the same way as before, only this time, the mould was made from vulcanized rubber.

The Melting  Pot
The Melting Pot
Pouring the  Metal into the Mould
Pouring the Metal into the Mould
The Electro-Plating Process

The final stage of producing the silver and gold medals was the plating process.

After the cast medals were washed to remove any dirt and grease, they were attached to copper wires and hung in the plating bath, to await electrolysis.

When the medals were at the right temperature, heated plating solution was added to the bath and the castings lowered into the solution. The solution then coated the casting in the desired finish and after cooling, the castings were removed and washed.

The reproduction process was then finished.

The Castings
The Castings
The Royal  Society Cook Medal Commemorative Medal (Replica)
The Royal Society Cook Medal
Commemorative Medal
(Replica)
The Packaged Medal

To produce a finished product to be sold in the museum shop, a printed backing card for the medal was also produced. With text provided by Phil Philo, the Senior Museum Curator, the reverse of the card outlines a description and history of the Captain Cook Medal together with a short synopsis of the life of Captain James Cook.

On the front of the card is the image "The Death of Captain Cook, Kealakekua Bay, 1779" by John Webber.

Finally, the medal was placed in a plastic sleeve, ready for sale.


Jonathan Williams, Sales Manager, Westair Museum Reproductions www.westair.co.uk

The reproduction medal can be purchased from the Captain Cook Birthplace Museum for £4.99 plus £1.00 postage and packaging in the UK and £3.00 elsewhere. Please make cheques and international money orders payable to "Middlesbrough Council" and post your order to the Captain Cook Birthplace Museum, Stewart Park, Marton, Middlesbrough TS7 6AS, UK

Originally published in Cook's Log, page 18, volume 32, number 3 (2009).

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