Iron and Conservation
steel and modern arc welding techniques have largely supplanted traditional
wrought ironwork. Chris Topp, a blacksmith in the ancient tradition,
looks at the historical development of the material and the need for
its continued use in conservation work today.
12th century iron bound door of Stillingfleet Church (left) and
its replacement made by Chris Topp and Co (right).
the Romans came, Britons were noted for their iron jewellery; an expensive
metal in literal terms, for the time and labour expended to make even
a small cinder of iron. Early wrought iron was made in the fire from
ore and charcoal. The heat was sufficient for the charcoal to reduce
the iron oxide to iron, but not to melt it. As a result the silicate
slags were included, not refined away as we might do now, but entrained
in the fibrous structure of the material. For this reason, the old
irons have lasted for hundreds of years. Iron may corrode, but not
its coating of silicate slags.
little survives because wrought iron may be repeatedly recycled and
benefits from reworking. Scrap could be bundled, heated until it glowed
white hot, and forged again by hammering into a solid mass to produce
an iron of a higher quality.
earliest surviving architectural ironwork in this country is probably
Norman, such as the portcullis, 'ex solido ferro', at Raby
Castle and barred treasury windows as at Canterbury Cathedral. Doors
too were often strongly bound with iron, frequently of a decorative
nature, such as the famous example of Stillingfleet Church, illustrated
above. Dating from c1145, it has only recently been renewed. The original
is conserved within the security of the church.
the exquisite precision of the locksmith and the armourer, to the
prosaic work of the mender of ploughs and the shoer of horses, the
art of the blacksmith developed. Little of this early architectural
ironwork is typical. The catch of a door or the bar of a window for
example, were more or less ornamented according to the whim of the
smith and as today, the available budget. Familiar types emerged,
such as the Suffolk latch, and various forms of hinges. Frequently
inventive, often crude, but always fashioned in accordance with the
nature of the iron.
the introduction of blast furnaces in the 15th century the availability
of wrought iron increased. Craftsmanship reached new heights in the
period of Great English Ironwork which started in 1690 or thereabouts
with the arrival of a Belgian, Jean Tijou. Some of the finest examples
of the period include his own work, such as the screens at Hampton
Court, and the work of his disciples such as Thomas Bakewell's garden
arbour now known as the 'Birdcage' at Melbourne Hall (1707-1711),
William Edney's St. Mary Redcliffe gates (c1710), and the Davies Brothers'
gates at Chirk Castle (1715-1721).
change was toward a freer use of beaten sheet metal ornamentation
applied to the bars to form baroque leaf-work, swags, masks and all
manner of delights. The techniques were no doubt derived from armoury.
The material was superb, not only for its ability to accommodate deep,
cold, repoussť work, but also for its persistence, for much of what
we can see today has weathered nearly 300 years.
accurately recreate items from the past, we must, even today use materials
and methods similar to those used then. Draughtsmanship is a thing
of the modern age, so too are obsessions with dimensions, symmetry
and squareness. The delicate lace work of the Golden Gates at Chatsworth
is no worse for the absence of a straight line or a square corner.
Built without drawings, held together with thousands of tiny rectangular
rivets, all different sizes, filed, no doubt, by a team of complaining
apprentices. Not easy to restore, but made infinitely more difficult
by the attentions of an arc welder of our own time, in the interest
of a former standard of 'restoration'.
iron of this period is now referred to as charcoal iron, a highly
carburised form of iron which was made by constant reworking in the
fire. It was even hardenable, unlike the puddled irons of the 19th
century, and there is no substitute for it. Only very recently has
this iron been made again for the conservation industry. It is available
in sheet form.
Ironwork took its course through the 18th century, from Baroque to
Rococo, and into a more austere era of mechanisation.
CAST IRON AND THE VICTORIAN AGE
iron has been known to the Chinese since before Christ, and was in
general use in Britain in the 16th century, mainly for items like
ordnance, firebacks and cooking pots. It was not until the 18th century
that any large scale use in architecture became apparent. The Adam
brothers experimented with cast iron. At first it was used as an ornament
to wrought ironwork. It was not however until after the foundation
of the Carron Ironworks in 1759 that the headlong rush into all things
of cast iron began, so familiar to us from the 19th century.
enforced new requirements for design, strength and accuracy. The carefree
blacksmith became a technician. Ornamental work too became accurate,
made to drawings, and characterised by squareness and symmetry. New
industrial methods brought mass produced puddled wrought iron, rolled
bars of consistent section, and new sections such as angles and tees,
as demanded for the construction of the new iron ships.
century ironwork was, however, by no means devoid of fun, as can be
seen from the railings of the London Law Courts, the Albert Memorial,
Holyrood House, and railway ironwork such as Great Malvern station,
as well as from the later glories of art nouveau and arts and crafts
iron, with its high tensile strength came again to the fore in the
Railway Age. Shipbuilding practices of fabricating structures by rivetting
together rolled wrought iron sections, came into use in building,
particularly in bridge building for the railways. Riveted plate girders
and latticework could span greater distances and carry heavier loads
than cast iron structures as tragically illustrated by the collapse
of the first Tay bridge in 1878. The wrought iron plate girder became
the basic device of building. Assembled into a dynamic framework until,
in America, buildings which seemed to scrape the sky became possible.
THE EMERGENCE OF STEEL
its higher carbon content and greater hardness, the value of steel
had been recognised since the earliest days of iron making. But it
was slow to produce and expensive. In 1856, in an attempt to mass-produce
wrought iron and by-pass the established hand puddling process, Henry
Bessemer stumbled upon mild steel, an even stronger, more consistent
material. The Bessemer process enabled large batch production, and
by 1876 mild steel was cheaper than wrought iron, gradually replacing
it for structural purposes. However the material was rather more prone
to corrosion, and in cases where durability and resistance to weathering
were paramount, wrought iron held its own for nearly another century.
general fall in standards since the War, and the inexorable process
whereby everything must be the cheapest, not only did away with the
production of wrought iron, but we very nearly lost the art and skills
so important to the working of the material.
the years technological improvements have made the manufacture and
working of ironwork much easier. However for the conservation and
replication of old ironwork we should bear in mind that only techniques
similar to those extant when the particular piece was originally created
will produce a thoroughly accurate replica. If a skill is not exercised
it will be forgotten, and with it the ability to create in the manner
of the past. The conservation of skills is perhaps just as important
as the conservation of the artefacts.
the use of modern mild steel in the conservation of wrought iron work
be permitted there will also be a tendency to compromise on technique.
Mild steel does not for example, lend itself so readily to welding
in the fire. Furthermore there is a tendency to use modern, mass-produced
sections, which are unlikely to match the imperial dimensions used
in the past.
to the 19th century, sections of wrought iron were forged to shape,
which gave them a more varied form and surface texture. By comparison
restorations in mild steel will appear relatively lifeless and the
result will be inconsistent with the texture of the original.
wrought iron is a material with a proven record of longevity which
will prolong the intervals between successive restorations. It is
true that its cost is higher but in many cases the cost of the material
is small in comparison with the cost of skilled labour, all of which
will be lost as the mild steel rusts away.
iron is currently available for restoration work, primarily through
the recycling of old material. Although sources of early charcoal
iron are limited, there are vast quantities of 19th century material
available from redundant and demolished structures such as bridges,
which can be reforged. An increase in demand for wrought iron for
conservation work could also make the production of charcoal iron
viable. Campaign for Real Iron!
article is reproduced from The Building Conservation Directory, 1994
CHRIS TOPP of Chris Topp & Company Wrought Ironworks Limited
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