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Sticking plaster

technical & practice - This month's restoration article looks at the pedigree of plaster and stucco and those involved in its development

The wonderful world of lime-rich render is part of our verbal archaeology, and every day we unwittingly relate to its origins. 'Plaster' might be defined as 'mouldable but usually level cementing material'. The Greek 'plastos', to mould or spread thin, comes from the same root as the Latin 'planus', spread flat. It evolved into 'emplastrum', a plaster (poultice, hence medical 'plaster'), which finally resulted in 'plastre', English and French medieval wall plaster. Modern 'plastic' has inherited the historic meaning of mutability.

Now 'stucco' seems a specific Italian word, probably coined with an inspired flourish during the Renaissance. But the Italians just applied a new meaning to another common stem. A dictionary of etymology will yield something like 'Stucco- n.

external plaster (Italian). Compare with Old High German stukk/stucki:

crust, piece, fragment. Also Middle English, stokki: made of wood.' Never mind our linguaphile ancestors, the German term is more prophetic as it anticipates that everything stucco will turn - if damp and exposed - into a fragmentary piece of crust.

It is remarkable how long plaster can take to get crusty in stable or dry conditions. Painted and delicately moulded lime plaster has survived for thousands of years around the Mediterranean. For the architectural busperson's holiday, one of the most remarkable and least-known survivals is at Ostia Antica (pictured above), ancient Rome's port, where a virtually complete bar/diner survives from the second century AD, its plaster complete with frescoes of food and still bearing the customers' toga rack. At the town's theatre, the soffits of the entrance tunnels bear traces of plaster in geometric relief patterns.

In about 30 BC, Vitruvius set out the basics of preparing the stuff to a formula which scarcely changed for almost 2,000 years:

'[Plasterwork] will be done properly if clods of first-rate lime are burned in the kiln, then, as it is softened over many days the remaining liquid, forced to boil away, will bake the clod to an even degree. If it has not been softened all the way through, but is used when only recently fired, then, when applied, it will develop blisters, because it has raw grains hidden inside. If these grains are put to work without having been softened to an even degree, they dissolve and break apart the finish of the plasterwork. If the softening has been done reasonably, and the work is to be prepared with care, take an axe, and chop through the softened lime to its core as it lies in the pit, just as if it were wood being chopped. If the axe meets with granules then the lime is not yet ready.

When the tool comes through dry and pure, it indicates that the lime is weakened and parched. When it is rich and properly softened, then, clinging all around that tool like glue, it shows that it has been tempered in every respect.

Then get the machines ready and set in the ceilings of the rooms?' Another long tradition is the plasterer's mate. In 1253 at Westminster Abbey we meet Adam the plaster, with his assistant (actually, Ada dealbatore cum serviente). It says something for the plasterer's status that he was mentioned by name among 31 anonymous marblers, two unknown glaziers and 13 nameless carpenters. Medieval painters used plaster and glue to form gesso, which was moulded to cover frames and to both achieve a ground for boards and heighten details of paintings. Plaster was also incised and painted to represent precious stones or mosaic, on tombs like that of Edward the Confessor, also part of the mid 13th century work at Westminster Abbey.

But the Middle Ages were not the high point of English plasterwork.

Much of lowland England built its humble dwellings from earth, rather than prepared plaster, and one of the few remnants of a long tradition is the thatched clay wall at Ashwell, Hertfordshire.

The 16th century developed the art of plastering into something quite distinct. One of the earliest importations of European stucco work was Cardinal Wolsey's adoption of sgraffito from Renaissance Italy. This technique, of painting black soot-based pigment or red ochre onto plaster which was incised and scraped to reveal white arabesque designs, featured from Milan to Rome, but particularly Florence, over whole external walls or, more usually, over arcades. It was a material recommended for cardinals in a book of 1510 called De Cardinalatu: the A-Z of how to be a cardinal, in which Chapter 2 explained the ideal cardinal's palace.

I come from Alabaster? Among other of Wolsey's Italianate innovations, he also brought geometric ceiling battens into vogue. His own examples were timber battens with arabesques of leather machÚ slid into a rebate along the underside, the junctions punctuated with gilded wooden knobs and lead leaves. Thereafter, especially once Serlio published his illustrated Book IV in 1537, stalactitic geometrical plaster ceilings became all the rage, and remain the greatest manifestation of the material in England.

Elizabethan plaster of Paris used burned alabaster instead of lime.

John Harrison observed: 'Within their doors, such as are of ability do oft make their floors and parget of [?] plaster of Paris, whereof in some places we have great plenty, and that very profitable against rage of fire.

In plastering likewise of our fairest houses over our heads [. . . ] we cover all with plaster, which, beside the delectable whiteness of the stuff itself, is laid on so evenly and smoothly as nothing in my judgment can be done with more exactness.' Such enthusiasm spawned the celebrity plasterer. Sir William Cavendish wrote to Sir John Thynne at Longleat in 1555: 'Sr I understand that you have A connyng plaisterer at Longlete wch hath in yor hall and in other places of yor house made Dyvse pendaunts and other pptye thyngs [?] I woolde pray you that I myght have hym in Darbyshere.' After his death five years later, Cavendish's widow, the accomplished heiress Bess of Hardwick, was still pressing Thynne for his man's skills: 'Thies are even to desire you to spare me your plaistere that flowered your halle whom I wold gladly have furthwith to be sent either to my howse at Chattesworthe - Or elles to London that I may sende him downe with all spede myselfe.' Stucco, or hard external render, became used for figurative high-relief work after Raphael somehow formulated the recipe in Rome. Henry VIII's Nonsuch, begun in 1538, was busy with Italian and French craftsmen modelling surfaces in slate and stucco, to such a high standard that well over a century later it was deemed as good an example of stucco as existed in England, confirmed by the fragments found in excavations more than 40 years ago.

It is worth asking to what extent 'pargetting' (a term once common for all manner of decorative plasterwork but now restricted to the moulded external plasterwork of East Anglia) was influenced by the stucco of Nonsuch, for it seems to have started at the end of the 16th century as an honest means of decorating thick plaster surfaces, often with moulds, which were once ubiquitous before the Victorian interest in naked timbers.

The Renaissance ranking of materials reinforced the burgeoning attitude that stone should supersede the socially awkward display of outmoded timber.

This 'keeping uppe with ye Joneses' led to the covering of timber houses, including projecting jetties, with thick stucco characterising masonry blocks.

The Elizabethan version of Bradstone could surely have kidded nobody.

Nevertheless two centuries later, Georgian terraces in stone-poor areas are everywhere to be seen with stucco rustication covering stock bricks on the ground floor yielding to a better quality brick above.

Split plasterwork Robert Adam's interiors are synonymous with the plasterwork executed by his master plasterer Joseph Rose.

Syon House in Middlesex contains a shockingly accomplished array of 18thcentury ceilings, in an age when a new array of preserved ancient coloured plasterwork was opening up to antiquarians at Pompeii and Herculaneum.

Adam himself recorded Diocletian's palace at Split with an archaeological eye. So it is perhaps ironic that his lacy plasterwork designs were coloured in shades of sugared almonds.

Plaster lost none of its popularity in the 19th century, despite the drive to cement-based Portland mixes and the truly horrible liquid brown rock made from pulverised septaria that was Parker's Roman Cement. At Harlaxton Manor in Lincolnshire, Salvin's neo-Baroque staircase was laden with garlands and ropes and billowing fabric all dipped in plaster and allowed to harden.

Victorian plasterwork at its best recovered its ancient use as a medium for painted surfaces, especially when it was used by artists such as Clayton and Bell at Garton on the Wolds, Yorkshire. But it arguably reached its nadir in theatres, where quadrigas of muses spill out over Rococo balconies in an apparent attempt to compete with, rather than complement, the entertainment. Le Corbusier's reaction to precisely this type of undisciplined, extraneous and retrospective garnishing was one of the formative moments of the modern era.

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