Cistercian monks invented the process of making durable clay 'encaustic' floor tiles with an inlaid pattern in the twelfth century, but this skill was lost following the dissolution of the monasteries in the late 1500s. Although Wedgwood had patented encaustic pottery in the 1700s, the Gothic revival and restoration of churches in the 1800s resulted in experimental manufacture to rediscover the precise methods by which replica encaustic tiles could be produced. By 1843, James Newlands in 'The Carpenter's Assistant' wrote that 'encaustic tiles, of beautiful forms and colours, have again been introduced'.
 
In the forefront was William Godwin, born in 1813, whose skill with fired clay as manager of a brickworks at Ledbury saw him experiment in encaustic tiles, moving in 1849 to Lugwardine near Hereford where he was joined by his brother Henry who had been working at Maw Tile Co in Worcestershire.
 
The Godwin's encaustic tiles were made from the red clays of the Downtonian Red Marl of the Upper Silurian series. Gilbert Scott, the church-restoring architect, first used them in 1857 in Hereford Cathedral and by 1868 the Godwin Encaustic Tile Co stated that its tiles had been used in 300 churches, the Manchester Assizes and Birmingham Exchange. Clays from Broseley, Dorset, Wales and Cornish china clay were used for the white or coloured parts of the tile. Of course, the Potteries were not to be outdone, and Messrs Minton of Stoke-on-Trent also made encaustic tiles in the written account by Charles Tomlinson in The Useful Arts & Manufactures of Great Britain published in 1863. Godwin died in 1883, and many of his technical secrets appeared to die with him.
 
Minton's 1885 catalogue states, 'Tiles … all enamelled by a patent process known as Reynold's process which was adopted in 1848 by the late Herbert Minton. The process for the decoration of the tiles was early favoured by A Welby Pugin, the great restorer of Gothic Art, in the Houses of Parliament and in many other places, and the patterns in that style or ornament in this book are all from his hand'.
 
The Minton catalogue states that these tiles were used for every conceivable purpose ... except flooring: 'It should be understood that these enamelled tiles are not intended, and indeed are unsuitable for flooring tiles, which this firm does not manufacture. Mr Reynolds, patentee, was awarded 1st Class at the 1855 Paris Exhibition, and also at Vienna 1873, and has had the management of these works since 1848 although other manufacturers have lately adapted it, mostly in its simpler form ... '
 
The precise methods of manufacture of Victorian encaustic tiles are a mystery. Charles Tomlinson's account of the mosaic works of Mintons in Stoke-on-Trent, gave a detailed description which is published here in full:
 
'The revived taste for decoration with encaustic tiles has led to the invention of a number of ingenious processes for the production of these articles, with a facility and beauty of effect which were not capable of being attained by the ancient method. In comparing the old with the modern productions, it may perhaps be said that the former as much excelled the latter in beauty and variety of design, as the latter surpass the former in facility of production, and excellent workmanship.
 
The following account of this branch of manufacture was obtained during a visit to the extensive tile and mosaic works of Messrs. Minton, of Stoke-upon-Trent.
 
Encaustic tiles consist of a thickness of red clay with a facing of a finer clay, which bears the coloured ornament or device. The bottom of each tile is also covered with a thin layer of clay, different from the body, in order to prevent warping during the drying and baking.
 
The body of the tile is formed of red clay or marl obtained from Cobshurst, about four miles from Stoke. When dug out, it is left exposed to the air for about seven months. This is called weathering or wintering.
 
When brought into the manufactory, it is thrown into a tank and worked about in water, with a blunger. When divided to a certain extent, it is laded into another tank and blunged; then laded and blunged for a third time. It is then passed through sieves of various degrees of fineness, mixed with various compositions, and is then either dried into hard lumps and ground into powder at the mill, or evaporated at the slip kiln, according to one of two methods by which it is intended to be formed into tiles.
 
By Mr. Prosser's patent, the powder, as it comes from the mill, is placed on slabs of plaster-of-paris, slightly damped. It is then sifted through fine sieves, and, when subjected to intense pressure, the particles of the powder will unite into firm, solid, slabs or tiles. At the lower extremity of the screw of the press, is fixed a steel plate, of the size and pattern of the intended tile; this fits into a steel box of the same dimensions, the bottom surface of which is ribbed, and this, by impressing ribs upon the under surface of the tile, enables it to adhere more strongly to the mortar or cement in laying down the tiles for a pavement, or for covering a wall. A quantity of the clay is placed into the die of the tile press as that shown in the figure, the force exerted is equal to about four hundred tons; and a thickness of three inches of powder is compressed into a tile one inch thick, with sharp edges, and a beautiful polished surface. Tiles of various sizes and shapes are thus produced, the largest of which present a surface of forty two inches by nine inches; also such articles as tops for tables, eighteen inches in diameter, scale-plates for pork and butter-shops, twelve inches in diameter and upwards. Small ornamental buttons, and shirt-studs, are made in a similar way at smaller presses; also tesserae, for mosaic work of various shapes, colours, and sizes, forming, when put together, all the beautiful devices of which mosaic work is capable. When, however, the size of a tessera exceeds one and a half inches square, it becomes a tile. When these various article leave the press, they are put into a hot room for a week or two, and are then ornamented, glazed, and fired.
 
Such is the method of forming what are called dry tiles. Encaustic tiles are formed from the cIay after it has been evaporated in the slip kiln. It is wedged and slapped to get out the air, and then slapped into a block, of the form of a cube, or parallelopiped, and placed before the tile-maker, who cuts off and removes a square slab, by passing a wire through it; upon this, the facing of finer clay, coloured so as to form the 9round of the tile, is batted out, and slapped down; it is then turned over, and a facing is applied to the bottom of the tile to prevent warping; the tile thus formed is next covered with a piece of felt, and put into a box-press: a plaster of Paris slab, containing the pattern in relief, is then brought down upon the face of the tile, and impresses in the soft clay, or ground of the tile, the design which is afterwards to be filled up with clay of another colour. When the tile is removed from the press the name of the maker is stamped on the back. The filling up of the device is next performed in an ingenious manner. A quantity of slip or clay, in a semifluid state, is poured over the tile so as completely to conceal its surface; this is spread over with a knife, and then left for twenty-four hours, when the slip becomes tolerably hard. The tile is then placed on a small whirler, and the pattern and the ground are brought out by scraping away the superfluous clay, and leaving it only in the depression caused by the pattern mould. The whole is, lastly, made smooth, and polished with a knife, and any little defects corrected; the edges are squared and their sharpness rounded off with sand paper; the tiles are then ready for the greenhouse, where they are arranged on shelves, and kept at a moderate heat for about seven days. After this period, the tiles are further dried in a hot-house, at a good strong heat; they are then arranged in seggars, and fired as in baking pottery and porcelain, only about double the time is required for the purpose. The oven is left to cool gadually during about six days, and the tiles are then drawn in their finished state. These tiles contract in firing, about one eighth of an inch in every inch. The dry tiles contract about one sixteenth of an inch.'
 
In 1998 (when this article first appeared in SalvoNEWS) Nigel Barrett was specialist products manager at H & R Johnson in Stoke-on-Trent, responsible for its output of encaustic tiles, made along traditional lines with modern technology. H & R Johnson owned the Minton archive and assumed a pivotal role in restoration of old geometric and encaustic tile floors and walls.
 
The company started producing encaustic tiles in the 1970s in order to restore the floor of the Arts & Industry building in the Smithsonian Institute, Washington. This resulted in research into the secrets of encaustic tile production. The materials used were close to the originals - highly silaceous marls, with a refined silicate body, essentially China clay. Early wall tiles were 'marly' . Nigel Barrett could tell which tilemaker made an unmarked old tile by the nature of the clay used.
 
Early encaustic tiles usually consisted of a sandwich of red brown marly clay on the upper and lower face, with lighter finer clay between to reduce warping during firing of the tile, although very early Minton encaustics were not sandwiches. From 1830 to 1840 they were made entirely of clays local to Stoke, and were of an impressed red fired body with a very thin light buff clay used for the inlaid pattern. From 1840 a cheap red 'open' marl was used as the sandwich filler, with a thin finer clay either side. A common misconception is that the sandwich clay is allowed through to the upper surface to become part of the pattern. This was not invariably the case. Holes were often put in the underside of the tile to allow for a more even firing temperature through the body of the tile. This is not dissimilar to the reason for holes in old Bridgwater bricks.
 
A problem for encaustic tilemakers was in creating tiles of a good thickness - hence the sandwich. Mintons used to make tiles of an inch thickness, but H & R Johnson produced half inch thick tiles in the 1990s. The Godwins never produced sandwich tiles and, according to Nigel Barrett, were brilliant encaustic tilemakers whose technical expertise has never been superceded. No-one knows exactly how they did it.
 
Originally, Minton tiles were pressed using plastic, slightly damp, clays which needed a drying time before firing. In the late 1840s Minton bought the Prosser patent and moved to dust pressed tiles using fly-presses which meant that tiles hardly needed drying, thus speeding production.
 
Traditional colours were browns and yellows until the 1870s when blues, whites and greens were introduced particularly from 1890.
 
Around fifty to sixty factories were producing encaustic and geometric floor tiles by the 1890s, as well as the Boulenger Anneuil factory in France, and two or three in the USA. Mr Barrett thought that the rarest tiles were made by the Worcester Tile Co, possibly to designs by Pugin.
 
Flow techniques which allowed more than one colour to be introduced into the pattern, were rarely seen before 1910. Geometric tiles continued to be made through to the 1930s, but the market eventually died with the advent of lino.
 
When Johnson's recommenced encaustic manufacture the traditional colours, black and chocolate brown, were obtained by adding manganese to the marls. Blue and green were made by adding cobalt and manganese to a clay made from white feldspar, ball clay and china clay.
 
The pattern of tiles to be reproduced was scanned into a computer. The scans, which included the minutest imperfections in the original tile, were increased fractionally in size to allow for contraction during firing and then they were fed into a top secret computer-controlled cutter to pro- duce the dies for the tile moulds. A job that used to take two weeks took less than an hour and a half.
 
After the body of the tile was pressed, leaving the pattern impressed in the surface of the tile and a border of waste around the edges of the tile, the recesses were infilled and pressed within twenty four hours. They were then allowed to dry, under weights to prevent movement. As they dried the face was machined using a spinning head. For six weeks they were successively dried and machined four or five times until bone dry and 12mm thick. Then they were fired to 1100degC in one firing.
 
The chemicals in the colours used, particularly cobalt, result in some tiles, during firing, allowing the fluid clays running into one another. The hardest combination to fire was blue and white, hence the price of the blue and white greek key tile (see photo). The success rate for fairly standard tiles was 85% and these cost £13 each.
 
For most one-off restoration tiles the success rate was 40% and the cost was around £100 to make the moulds and £20 a tile. For difficult tiles the success rate was 10%. For the greek key blue and white - Johnson's most difficult tile - the success rate was 2% and the cost per square tile was £90, or £110 for a curved one! In contrast their cheapest tile was £1.50 for an inch square geometric.
 
Another glaze problem was the matching of the original raw lead frits of wall tile murals, which contained various shades of green, and which were unpredictable because they were 'highly reactive'. Johnson's simulated these using what was known as 'encapsulated lead' frits - with a lot of trial and error.
 
After a pattern of tiles had been successfully fired, each tile was individually cut to the precise finished size, and the whole design laid out on the workshop floor to check that everything fitted perfectly.
 
The cutting of tiles was skilled work, especially the curved ones, and took around three years for an employee to learn. In the 1990s H & R Johnson were believed to be the only company in the world producing encaustic tiles on a production basis.
 
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Written by Thornton Kay and first published 26 January 1998 in SalvoNEWS 158