The larger of these cannons, the siege cannon, was recovered from the Spanish Armada wreck of the Trinidad Valencera, off the coast of Co. Donegal. The Trinidad Valencera was a Venetian merchant ship that had been seized in Sicily in 1586 and forced into the service of Philip II of Spain. At 1,100 tonnes she was the fourth largest of the ships of the great armada of 1588, with which Philip tried to invade England. After a battle with the English and a violent storm, many ships from the fleet were wrecked around the Irish coastline.
The siege cannon was cast in 1556 by the Founder Royal, Remigy de Halut, in Brussels. It bears an inscription stating who made it, together with the arms of Philip II and is decorated with dolphins and stylised foliage. It is bronze, weighs 2.5 tonnes and would have fired a 41 lb iron ball. This was one of a number of siege guns that the 130-ship armada carried in preparation for the proposed conquest of England, together with 19,000 soldiers and their supplies.
The smaller ‘pedrero’ cannon from the Juliana was recovered off Streedagh Strand in Co. Sligo. The Juliana was one of three Armada vessels wrecked on this part of the coast in the storm of 21 September 1588, where they broke up and where the bodies of 1,000 crew members were later found.
The pedrero cannon was small and comparatively light in weight. It fired a large stone ball and would have been a ferocious weapon at close quarters in ship to ship fighting.
When the cannons were raised, they were completely impregnated with salt from the sea. Salt, when combined with oxygen and water in the air, causes rapid corrosion in metal, so the salt had to be removed before the cannon could be dried out. This was achieved by placing the cannons in tanks of fresh water, alternating between hot and cold to make the metal expand and contract to force the salt out. The last two washes were carried out with de-ionised water, to ensure that the salt content of the cannons was as low as possible.
The cannons were then dried out thoroughly and the painstaking work of cleaning off corrosion and concretions could begin; a process which took several weeks. The layers of dirt and corrosion had to be carefully removed mechanically with hand tools to reveal the original surfaces of the cannons under them. A thin coating of lacquer was then applied, followed by a coating of wax to protect the cannons while on exhibition at Collins Barracks.