Tinplate
Tinplate consists of sheets of steel coated with a thin layer of tin to impede rusting. Before the advent of cheap milled steel, the backing metal was wrought iron. While once more widely used, the primary use of tinplate now is the manufacture of tin cans.
Tinplate is made by rolling the steel (or formerly iron) in a
Formerly, tinplate was used for tin ceiling, and holloware (cheap pots and pans), also known as tinware. The people who made tinware (metal spinning) were tinplate workers.
For many purposes, tinplate has been replaced by
History of production processes and markets
The practice of tin mining likely began circa 3000 B.C. in Western Asia, British Isles and Europe. Tin was an essential ingredient of bronze production during the Bronze Age.[1][circular reference] The practice of tinning ironware to protect it against rust is an ancient one. This may have been the work of the whitesmith. This was done after the article was fabricated, whereas tinplate was tinned before fabrication. Tinplate was apparently produced in the 1620s at a mill of (or under the patronage of) the Earl of Southampton, but it is not clear how long this continued.
The first production of tinplate was probably in
The slitter at Wolverley was Thomas Cooke. Another Thomas Cooke, perhaps his son, moved to Pontypool and worked there for John Hanbury.[3] He had a slitting mill there and was also producing iron plates called 'Pontpoole plates'.[4] Edward Lhuyd reported the existence of this mill in 1697.[5] This has been claimed as a tinplate works, but it was almost certainly only producing (untinned) blackplate.
Tinplate first begins to appear in the Gloucester Port Books (which record trade passing through
Further mills followed a few years later, initially in many iron-making regions in England and Wales, but later mainly in south Wales, most notably the
Despite this blow, the industry continued, but on a smaller scale. There were 518 mills in operation in 1937, including 224 belonging to Richard Thomas & Co. The traditional 'pack mill' had been overtaken by the improved 'strip mill', of which the first in Great Britain was built by Richard Thomas & Co. in the late 1930s. Strip mills rendered the old pack mills obsolete and the last of them closed circa the 1960s.
Pack mill process
The raw material was
This was then rolled until it had doubled in length. The plate was then folded in half ('doubled') using a doubling shear, which was like a table where one half of the surface folds over on top of the other. It is then put into a furnace to be heated until it is well 'soaked'. This is repeated until there is a pack of 8 or 16 plates. The pack is then allowed to cool. When cool, the pack was sheared (using powered shears) and the plates separated by 'openers' (usually women). Defective plates were discarded, and the rest passed to the pickling department.
In the pickling department, the plates were immersed in baths of acid (to remove scale, i.e., oxide), then in water (washing them). After inspection they were placed in an annealing furnace, where they were heated for 10–14 hours. This was known as 'black pickling' and 'black annealing'. After being removed they were allowed to cool for up to 48 hours. The plates were then rolled cold through highly polished rolls to remove any unevenness and give them a polished surface. They were then annealed again at a lower temperature and pickled again, this being known as 'white annealing' and 'white pickling'. They were then washed and stored in slightly acid water (where they would not rust) awaiting tinning.
The tinning set consisted of two pots with molten tin (with flux on top) and a grease pot. The flux dries the plate and prepares it for the tin to adhere. The second tin pot (called the wash pot) had tin at a lower temperature. This is followed by the grease pot (containing an oil), removing the excess tin. Then follow cleaning and polishing processes. Finally, the tinplates were packed in boxes of 112 sheets ready for sale. Single plates were 14 inches by 20 inches; doubles twice that. A box weighed approximately a hundredweight.[7]
What is described here is the process as employed during the 20th century. The process grew somewhat in complexity with the passage of time, as gradually it was found that the inclusion of additional procedures improved quality. The practice of
Strip mill process
The strip mill was a major innovation, with the first being erected at
The strip mill had several advantages over pack mills:
- It was cheaper due to having all parts of the process, starting with blast furnaces, on the same site.
- Softer steel could be used.
- Larger sheets could be produced at lower cost; this reduced cost and enabled tinplate and steel sheet to be used for more purposes.
- It was capital-intensive, rather than labour-intensive.[9]: 155–170, 265–280
Further reading
- Gibbs, F.W. (21 November 1950). "The rise of the tinplate industry. I. The tinplate workers". Annals of Science. 6 (4). Informa UK Limited: 390–403. ISSN 0003-3790.
- Gibbs, F.W. (28 March 1951). "The rise of the tinplate industry.—II. Early tinplate manufacture to 1700". Annals of Science. 7 (1). Informa UK Limited: 25–42. ISSN 0003-3790.
- Gibbs, F.W. (28 March 1951). "The rise of the tinplate industry—III. John Hanbury (1664–1734)". Annals of Science. 7 (1). Informa UK Limited: 43–61. ISSN 0003-3790.
- Gibbs, F.W. (28 June 1951). "The rise of the tinplate industry.—IV. An eighteenth century tinplate mill". Annals of Science. 7 (2). Informa UK Limited: 113–127. ISSN 0003-3790.
- W. W. Minchinton, The British tinplate industry: a history (Oxford 1957).
- P. Jenkins, 'Twenty by Fourteen': a history of the south Wales tinplate industry 1700-1961 (Gomer, Llandysul, Dyfed 1995).
- D.A. Irwin, 'Did late nineteenth century U.S. tariffs promote infant industries? Evidence from the tinplate industry' (NBER working paper 6835 1998)
See also
- Plating for other processes for plating metals.
- Tinsmith
- Tinware
- Terne plate, a cheaper version, but not food-safe, using a mixture of lead and tin.
Footnotes
- Tin sources and trade in ancient times#Ancient sources
- ^ P. J. Brown, 'Andrew Yarranton and the British tinplate industry' Historical Metallurgy 22(1) (1988), 42-8; P. W. King, 'Wolverley Lower Mill and the beginnings of the tinplate industry' Historical Metallurgy 22(2) (1988), 104-13.
- ^ King, 109
- ^ H. R. Schubert, History of the British iron and steel industry ... to 1775, 429.
- ^ Minchinton, 10.
- ^ Data extracted from D. P. Hussey et al., Gloucester Port Books Database (CD-ROM, University of Wolverhampton 1995).
- ^ Minchinton, 250-3
- ^ For this business see L. Ince, The Knight family and the British Iron Industry (1991).
- ISBN 9780671553357.