Saturday, 15 October 2011

The Construction of a Viking Shield; Part 2

Having sourced the correct wood, the task of assembling the shield began. The redwood was cut to 1 metre lengths, 145mm wide, and reduced to 1cm thick. The longitudinal edges were then scored and each adjoining edge applied with pearl glue to ensure good adhesion...
 The boards were then placed flat against two stable vertical uprights such as those of the garden shed (see image) and the adjoining edges then firmly pressed against each other, ensuring that there was contact along their entire length. The boards were then gently secured to the uprights with a couple of tacks, which also ensured that constant even pressure was applied to the join until the glue had set. The structure was built up in this manner until it was 1 square metre in size. Note: that the uprights were covered with plastic to prevent the structure adhering to them.

As seen in this image, pearl glue is so called because it resembles
tiny amber pearls. Pearl glue, is the modern term in the UK for what is otherwise known as carpenters glue, hide glue or animal glue. It is an extremely strong glue, but is not, however, especially resistant to damp or moisture.[1] Being made from the boiled down remains of animals it is one of the oldest glues known to man[2] and if the 10th century Scandinavians were going to use glue this would almost certainly be it.

It is argued that the use of hide glue in every aspect of the construction of the shield represents a significant weakness in the shield simply because it is vulnerable to moisture and damp conditions. It has been argued that such shields were not expected to last long in battle, because of their apparent fragility. That may be, but the point is how long were they expected to last before they were used in battle. A shield will be of little use in battle if it cannot withstand the elements. This raises an interesting question which will be addressed later.

Having left the completed structure in situ for 24 hours, a circle of 85cm diameter was drawn onto the wood before carefully removing the structure from the uprights. After ensuring that the structure was free to move, it was lifted up by the corners of the top board. There was no evidence of poor adhesion, in fact quite the opposite as the motion of manoeuvring the fragile boards towards the work bench was enough to effect it in such a way as to make it make it gently sway back and forth.

From this experience it was evident that the structure, as a whole, had so little rigidity that some form of substantial reinforcement was necessary. Placing the ‘shield’ on the work bench, and using a jigsaw, the excess wood was carefully removed, including the centre hole. This made the structure lighter and easier to handle. At this point the shield was left on the work bench for a few hours. (See image right.)

It is appropriate at this juncture to return to the question of the weight of the shield. Pinus sylvestris, when green, has a moisture content of about 70%. This equates to a mean density of approximately 800kg/m³.[3] During the kiln drying process which can last for a period of 7 to 8 months the moisture content is reduced to around 12%, which equates to a mean density of 520kg/m³.[4] However, because the equilibrium moisture content is dynamic, being susceptible to changes in the local humidity and
temperature, this figure could rise slightly.[5]
Kiln dried 520kg/m³ divided by 100 = 5.2kg/Sqm or 11.44lbs /Sq m.
Green 800kg/m³ divided by 100 = 8.0kg/Sqm or 17.6lbs /Sq m.
The diameter of the shield is 84cms. (Area = Pi*r²).
Area = 3.142 * 1764cm = 5542.5 Sq cm.
1 m² = 10,000cm². Shield has a surface area of 5,543 cm², which (rounding down) equates to 55% of m². From these figures it can be calculated that: Shield made of Kiln dried Pinus sylvestris = 6.292lbs (6.3lbs) (2.8Kg)
Actual weight of shield, with hole removed for boss = 6.1 lbs (2.7Kg)
If shield had been made of ‘green’ Pinus sylvestris = 9.7lbs (4.4Kg)

Not an insignificant figure, and the differential would reduce if the ‘green’ wood had been subject to air drying.

Having been left lying flat for a few hours on the work bench, because of the anisotropic nature of wood[6] and moisture and temperature equilibration, dimensional change had occurred. As wood shrinks least along the longitude this meant that each board had provided longitudinal stability to its neighbour. As the boards had been flat sawn, tangential shrinkage had occurred causing a cup warp with the result that the ‘shield’ had arched laterally.[7] The distance from the surface of the workbench to the apex of the arch being about 2 inches (50mm).

At this stage, it is argued that not even the attachment of a boss, grip and rim binding would have been wholly effective. To impart the structure with enough strength and rigidity to make it functional for the purpose it was design for, would, it is argued, require the structure to be faced on one side or both with either linen, raw-hide or leather or a combination of these.
In respect of linen although there are some modern sources that suggest that linen could have been used to face Anglo-Saxon / Viking shields, the author at the time of writing this article is unable to find any hard evidence that linen was ever or actually used in this context [8]; that does not mean, however that it never was, and as the purpose of this exercise is to learn about the construction it was decided to face both sides of the shield with linen canvas.
...to be continued...
(This work is an extract from a paper entitled "The Construction of a Viking Shield" by Anthony C. Lewis BA(Hons) MCFM JP.   The full work can be found HERE )

[1] Savage, D. 2010
[2] Ibid
[3] Davies, I. 2008.
[4] Ibid.
[5] Swell, R. 2011.
[6] Woodford, C. 2011
[7] Wengert E.M. and Meyer, D. 1993 in Woodweb. 2001.
[8] ss, E.M. (2011) Education Officer. Museum of Cultural History, University of Oslo.

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