As we found them
September 13, 2019

Conserving a cannon

By: By Peter G. Underwood, 29 August 2018
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There is a considerable, and important, difference between conservation and restoration. “Conservation” is concerned with the stabilisation of an object so that further deterioration of its condition is slowed or arrested, whereas “restoration” seeks to return an object to a former condition.

Cannon made of cast iron are vulnerable to corrosion, this being most familiar in the form of surface rust. Iron guns can also suffer another form of corrosion, caused by the residue of black powder after firing, which is acidic and eats into the bore of the cannon and venthole, reducing iron to a “honeycomb” form and rendering the cannon unsafe to fire.

When recovered, conservation of a cannon commences with a visual inspection, aimed at assessing its condition, noting visible damage and any markings or decoration that could provide clues as to its provenance. Photography can provide a useful visual record but, unless specialised equipment is available, the images may not provide sufficient contrast to allow detail to show. This is why a careful visual inspection, note-taking and sketching may be essential to capture the available evidence.
Cannon Durr 9801 is a cast iron muzzle loader unearthed during excavation for cable-laying in Orange Street, Cape Town, on 4 September 2013. It was located just outside the African Pride’s 15 On Orange Hotel.

The gun was moved to the backyard of the Gardens Information Office and here it remained, encrusted with clay and gravel, and partly buried under stones and upturned park benches.

When examined, it was evident that the bore was packed with sediment and that the trunnions had been broken off — a major loss because the foundry identification mark would, almost certainly, have been cast in relief into the left-hand trunnion. However, using the dimensions and characteristics of the gun, it was possible to deduce (with a high degree of confidence) that it had been cast by the Finspång bruk (foundry) in Sweden. This foundry was responsible for casting most of the guns commissioned by the Dutch East India Company (VOC) and the Dutch Admiralties.

The style of the gun, and the sequence of decorative reinforcing rings, suggest that it was cast sometime in the period from the late 1600s to early 1700s. Durr 980 has a base ring diameter of 500 mm, a length of 2 810 mm and a bore of 140 mm, suggesting that this is an 18-pounder. If this is correct, then the find is of considerable significance because this calibre is rare for this period and no other gun with these dimensions has, so far, been found in South Africa.

The condition of the gun was such that conservation was needed if further deterioration was to be avoided: accordingly, Martin Venter (Chair of the Cannon Association of South Africa) and Desiree Doyle Venter agreed to work on it.
The first task was to move the gun to a suitable working area and this required the use of a hoist and several strong arms.
Then the heavy work of chipping rust commenced, always with care in case some foundry or other marks were uncovered. In this case, just in front of the vent, a VOC marking, and the letter “H” were discovered.
Once the loose rust had been removed, the next step was to apply a rust-converting paint, allowing this to dry overnight to leave a secure surface. This was then painted and now awaits a carriage.
The conserved gun will be placed in the Company’s Garden, between the restaurant and the Cape Town Heritage Trust building.
Peter G. Underwood
29 August 2018