BCD 2017

162 T H E B U I L D I N G C O N S E R VAT I O N D I R E C T O R Y 2 0 1 7 provide control samples of new tiles that accurately matched the originals in terms of decorative designs and colours. Materials testing to confirm the slip resistance, surface porosity and wearing characteristics of the new tiles was also carried out. It is important that in time, the new tiles should wear in a similar manner to the historic ones. Modern manufacturing techniques are based on those of Samuel Wright and Herbert Minton but with some obvious differences. Mechanisation of the clay milling process significantly reduces the health risks of manufacture. Modern kilns, fired by gas or electricity rather than coal or wood, make greater control of the firing process possible, allowing very precise matching of original colours, cutting waste and reducing the carbon footprint of manufacture. Better control of distortion allows the tile body to be made of one piece of clay, rather than in the three layers used by Minton. Craven Dunnill Jackfield was able to accurately match the artwork of the original tile designs and to make clays which, on firing, gave a precise match to the colour of the original materials used. New slate was sourced from the Valentia mine on the Iveragh Peninsula in County Kerry, Ireland, where the material used in the floors was originally extracted. Colour variations were noted between the new slate and the slate in the existing floors. This is possibly due to natural variation, although it is also probable that the colour of the original flags had changed due to the historic use of oil or wax in cleaning. The Hopton Wood quarry near Wirksworth, Derbyshire ceased production of building stone in 2009 but a small amount of stone was still available from reserves previously extracted and this proved sufficient for our needs. Mortar analysis formed the basis for the design of an appropriate modern mortar for the repairs. The properties of early cements varied considerably but they were very much weaker than modern Portland cement, being closer to an eminently hydraulic lime in strength. A hydraulic lime binder was therefore used in the repair work. An area in St Stephen’s Hall of approximately 47 square metres was identified for trial repairs. The repair methodology adopted for this trial was based on the following principles: • Tiles and stone that were in good condition, including tiles slightly chipped around the edges or with minor cracks not detracting from their overall appearance, would be retained in situ wherever possible. • Tiles that were badly damaged or that had completely or nearly lost their pattern (including tiles previously replaced with inappropriate substitutes or poorly repaired) would be replaced. Some panels of tiles would thus be replaced in their entirety. • Tiles that were partially worn with an estimated remaining life span of 15 or 20 years and which still displayed a complete pattern would be removed from areas of the floor which are otherwise badly worn and thus need complete replacement. These salvaged tiles would be used for the individual replacement of tiles of the same pattern in areas of lesser wear. • Worn or broken flags of Valentia slate and previous inappropriate replacements of historic Valentia slate would be renewed. • New tiles and salvaged tiles being reused would be bedded in a layer of mortar of a mix designed to be sympathetic to the historic fabric. Tiles would be bedded and pointed in a single operation. Working closely with DBR London to lift old pavements and re-lay them, Strategic Estates has carried out the programme without unnecessary disruption to the working of parliament or the reception of its visitors. A controlled environment working inside tents with vacuum air filters is employed to protect people, the built fabric and works of art within the palace. The trial was very successful. The methodology of complete lifting in some areas and piecing in repairs to others was clearly demonstrated. More recently, the repair and conservation of several more floors has been initiated, including those of the Members’ Entrance, Lower Waiting Hall, Central Lobby and the Royal Gallery. In January 1852, Pugin wrote a letter to Herbert Minton in which he said: ‘I declare your St Stephen’s tiles are the finest done in the tile way, vastly superior to any ancient work; in fact, they are the best tiles in the world and I think my patterns and your workmanship go ahead of anything’. The careful and respectful approach to revitalising the Palace of Westminster’s tiled pavements is one that strongly echoes that dedication to design and workmanship. Further Information Craven Dunnill Jackfield Limited www.cravendunnill-jackfield.co.uk L Durbin, Architectural Tiles, Conservation and Restoration , 2nd ed, Routledge, London, 2014 L Durbin, ‘Conservation and Restoration of Pugin Tiles at the House of Commons’, Context , 54, 1997 Gladstone Pottery Museum www.stokemuseums.org.uk/visit/gpm The Jackfield Tile Museum www.ironbridge.org.uk/our-attractions/ jackfield-tile-museum H van Lemmen, Tiles: 1000 years of Architectural Decoration , Abrams, New York, 1993 The Minton Archive www.themintonarchive.org.uk The Potteries Tile Trail www.thepotteriestiletrail.org Tiles and Architectural Ceramics Society www.tilesoc.org.uk/tile-gazetteer/ westminster.html For more information on the encaustic tile floors at the Palace of Westminster, please email architectureandheritage@parliament.uk . ADAMWATROBSKI BA(Hons), DipArch, DipConsAA, RIBA is the principal architect and head of architecture and heritage at the Houses of Parliament. Notes 1 Minton’s first encaustic pavement was laid in 1842 at the Temple Church, City of London. An early use of Minton’s tiles by Pugin was for St Chad’s Roman Catholic Cathedral, Birmingham in the early 1840s. 2 Grog also helps to prevent shrinkage. The tiles are stamped on the back: ‘Minton & Co Patent, Stoke upon Trent’. 3 Hopton Wood is a pale limestone which has been used as an indoor paving stone since the 18th century and polishes naturally to an eggshell finish. 4 Caput mortuum (literally ‘dead head’) is a dark purple-brown. 5 Minton also provided glazed, dust-pressed, block-printed (Collins and Reynolds original patent) tiles as an easily washable surface for the dado of the Strangers’ Smoking Room, now the Terrace Cafeteria servery. These tiles were repaired in 1994–6 by Jackfield Conservation Studio and the Decorative Tile Works. Repaired area, St Stephen’s Hall: note the small unrepaired section at bottom right Comparison between new and old tiles, Central Lobby