In Depth: The Killer Glazes

Léon Arnoux, the Minton company’s longstanding Art Director, is a prominent figure in the Minton Archive collection. As the driving force behind the company’s innovative Patent Oven his name appears frequently in that particular section of the catalogue, but his distinctive hand can also be found in recipe books, on Art & Design folio artworks, and throughout many other parts of the collection. Our latest In Depth article, published below, explores Arnoux’s involvement in reducing and controlling the use of lead glazes in the pottery industry and has been kindly provided to us by retired architect and local historian Michael Prendergast.

The Killer Glazes: The influence of a ceramicist from France and an Irish doctor on the health of pottery workers in England

Michael Prendergast · 16 minute read

Lead poisoning had a prolonged history of causing suffering for those involved in many trades over the centuries and across the world – particularly the pottery industry with its use of lead glazes.  This is the story of two people involved with Minton in the nineteenth and early twentieth centuries, who helped to change legislation in the United Kingdom effectively controlling the use of lead-based glazes.


The use of glazes has been known for a very long time and lead glazes were used by the ancient Egyptians on some of their pottery1 to produce a hard surface2. In many bibles we read that the potter used what is commonly translated as ‘anointing’ for finishing his pot.

The formula for this ‘anointing’ is not specified. ‘Anointing’ would not survive firing: this must be a glaze. In Poitou, France, circa 1757, the merchants who sweetened sour wines with lead oxide drew the attention of doctors to the sickness of saturnism – a poisoning, affecting also harvesters who drank cider poured from jugs glazed with lead3. The situation among workers in diverse industries, most of all in the English potteries in Staffordshire4, became so serious that many Parliamentary enquiries5 concluded that the use of a glaze without lead was essential, and the prohibition of the use of lead itself a priority. How this came to be, by the marriage of an Irish doctor and the daughter of a French ceramic artist of Toulouse, is examined in this article.

The Beginning and the Personalities

Antoine Arnoux was a potter managing a large factory at St. Sernin, Toulouse, France in the early nineteenth century6. He became connected to the Fouques, another important pottery family, through his marriage to Marie Rosalie Fouque on 7th March 1813. Their first son Joseph François Léon, known as Léon, was born in 18177. Antoine wanted his son to have an education above that of a potter and therefore he was sent by his father to Paris to study for a career as an engineer at the Central School of Arts and Crafts in Paris8. Antoine also wrote to his acquaintance Alexandre Bronginart, asking whether during the summer holidays Léon could study the art of painting in fusible colours at the pottery in Sèvres where Bronginart was the director9. This was granted and Léon worked diligently at Sèvres, developing his knowledge and craft.

Antoine Arnoux’s factory in Toulouse – 1832 Courtesy of © Musée du Vieux-Toulouse (inv. 001.0.48), photo J. Kerambloch

Formulae recorded in Léon Arnoux’s handwriting10 still exist at Minton for glazes (or varnish) drawn from his time at Sèvres. In these recipes are recorded metals to achieve the required colours – notably cobalt used by him to obtain a very deep blue. It was in search of pure cobalt that led him to travel to England to Evans & Askin11, colour merchants at Stoke-on-Trent in 1848. There he met Herbert Minton, owner of a ceramics factory. The two men found common interests and a position was offered to Léon in Minton’s works for trials in making hard porcelain. Arnoux went back to Saint-Gaudens-Valentine to collect his family and returned with them to Stoke-on-Trent in 184912.

Léon Arnoux’s career at Minton is very well told by Bernard Bumpus13 and the obituary written by Arnoux’s son-in-law Léon Solon adds details14. He notes Arnoux’s success in developing the revival of majolica for Mintons at The Great Exhibition of 1851 and The International Exhibition of 1862, which brought great financial rewards to the company. The lustrous glazes however included poisonous lead which Arnoux sought to alleviate through the use of fritt and cleaner working conditions.

Léon Arnoux soon after his arrival in Staffordshire (undated), author’s collection

Twenty years later an Irish doctor arrived in Stoke-on-Trent. He was born in Saint Helena, son of a garrison officer John Prendergast15 who knew the Emperor Napoléon. A descendant, Christopher Prendergast, possesses today an ebony walking stick with silver decoration given by Napoléon to John at Chubbs Farm on the island which the Emperor often visited.

The doctor was William Dowling Prendergast. He qualified in Dublin with two masters degrees and the Diploma of Public Health from the University of Manchester. Following his studies Prendergast arrived in Stoke-on-Trent and opened his surgery. In his medical practice he found that a number of his patients were dying, men and women, through lead poisoning. He took action and in 1891 attracted public attention to the unhealthy workplaces by publishing an article in the ‘Staffordshire Advertiser16 about ‘The Modern Potter from a Sanitary Point of View’, in which he contradicted the Registrar General’s statistics that omitted the deaths of all women. Prendergast demanded the use of leadless glazes. His further concern outlined the need for far cleaner working surroundings and personal cleanliness from the potters themselves.

William Prendergast as a young man, circa 1880, (author’s collection)

In 1898 he then published a book titled ‘The Potter and Lead Poisoning’17, on page 10 he wrote ‘I have been assured by a gentleman who managed a manufactory of earthenware on the continent that the custom there was to fritt together all the ingredients of the glaze and that in his works lead poisoning was unknown’. This must be Arnoux, William having married Léon’s daughter Alice in 1888. Whilst Prendergast’s text is concerned with the physiological effects of lead and remedies he also offers a formula (p.53) of his book that puts borax in place of lead. This coincides with Arnoux’s knowledge probably passed by him to his son-in-law.

As a doctor Prendergast found that many of his patients died aged 22-27 years old, poisoned by lead absorbed either by their hands or their lungs18. Workers dipping articles in glaze were as vulnerable as those who breathed the powdered glaze19. Symptoms such as colic could lead to blindness and partial paralysis as well as other disabling effects and are described in detail in his British Medical Journal article, (1910), 14 May, p.1164-1166. Appointed as a surgeon to give certificates to patients to draw benefits under the Acts of Parliament governing industrial injuries he also found cases where miscarriages and still births followed after exposure to lead.

His articles in the press aroused national interest and Prendergast was summoned as a witness at the Parliamentary Committees in 1899, 1908 and 1910 to investigate the effects of lead in china manufacturing.

It is certain that alternatives to lead formulae existed at that time. A patent was granted in 1839 to a C W Turner and Herbert Minton for a formula of flint, biscuit paste, calcium sulphate and china clay, ground and mixed as a powder. There were others, for example in 1848 to Skinner & Whalley, in 1862 to Wallis and in 1864 to Johnson20. Léon Arnoux tried Johnson’s formula (recorded in his recipe book, page 78, held in the Minton Archive), but in this instance he remarked that ‘this does not work’.

All this together with Brogniart and Salvétats’ experiments on ancient glazes are written up by William James Furnival in his book ‘Researches on Leadless Glazes’. It was published contemporaneously with Prendergast’s ‘The Potter and Lead Poisoning’. Furnival carried out extensive experiments and as a clay merchant and consultant ceramicist his positive results using lead free glazes should have been heeded.


  1. (accessed 11 July 2018)
  2. Adams W. Y. (1986), Ceramic Industries of Medieval Nubia, p.585, University Press of Kentucky, p.585, 1986
  3. Meiklejohn A. (1963), The successful prevention of lead poisoning in the glazing of earthenware in the north Staffordshire potteries, British Journal of Industrial Medicine, Department of Industrial Health, University of Glasgow, 1st July, p.171. (accessed 11 July 2018)
  4. Meiklejohn (1963), op. cit. p.171 et seq
  5. Parliamentary Archives – 1896, 1908, 1910, Committee on Lead, etc., in Potteries
  6. Beaux-Laffon, M-G. (2001), Une Grande Manufacture Pyrenéenne St-Gaudens Valentine Pyregraphe, Aspet, p.40
  7. Arnoux, L., Génealogie de la Famille Fouque-Arnoux, undated manuscript, p.13 (author’s collection)
  8. Op. cit. Beaux-Laffon (2001), pp.40-42
  9. Solon, L. (1902), The Late Mr. Léon Arnoux, of Stoke-on-Trent, A Biographical Sketch, Staffordshire Advertiser, 6th September, p.7
  10. Stoke-on-Trent City Archives, SD 1705/MS1428, manuscript, Stoke-on-Trent 1849
  11. Solon, L. (1902), op. cit., p.7
  12. Beaux-Laffon (2001), op. cit. p.98. The relocation to England by Arnoux was also beneficial because the 1848 revolution in France had resulted in the bankruptcy of the Fouque-Arnoux firm
  13. Bumpus B. (2001), Actes du Colloque de Martres-Tolosane (31) 21022 Sept.
  14. Solon (1902), op. cit. p.7
  15. Henry, K., (2018) Email to Crosse P., 11 July: as shown in the Roman Catholic Index Book, 8th February 1859, Saint Helena Archives > cf. Staffordshire Advertiser (1924), Distinction for Researches into Lead-poisoning 14th June
  16. Staffordshire Advertiser (1891), The potter from a sanitary point of view, 22 July, p.2
  17. Prendergast W. D. (1893), The Potter and Lead Poisoning, ‘Prendergast W. D., MD, MCh, MAO, Royal University of Ireland, Dip. PH University of Manchester’: Marshall Russell, London
  18. Personal communication between the author and his father, Maurice Prendergast
  19. Prendergast, W. D. (1893), op. cit. 35-36
  20. Furnival, W. (1898), Researches on Leadless Glazes, Staffordshire, Furnival, W.