Evolution of the Tin Can

Evolution of the Tin Can

Tinplate has a long and interesting history as a packaging material, in fact, tinplate containers were used for preserving cooked meats as long ago as the eighteenth century. However, it was not until the first decade of the nineteenth century that the principles of canning as we know them today were first put into practice by the Frenchman Nicolas Appert. In 1809 he won an award of 12,000 francs from Napoleon I for being the first to devise a successful technique for preserving foodstuffs. His process, disclosed in a book which he published in 1811, consisted of enclosing and sealing the food products in suitable containers so that air was excluded and subsequently cooking the food in the filled and sealed jars for a suitable period. Appert used glass vessels, but a Manchester business man Peter Durand patented the use of a Tinplate Container.
The first true canning factory in the world was set up in Bermondsey, London, by two English engineers, John Hall and Bryan Donkin, using tinplate from the Worcester Tinplate works; by 1812, a variety of perishable foods packed in “boxes of tinned iron” were on sale to the public. Cans of this type were taken by Captain Parry on his voyages of Arctic Exploration and on return from the first voyage, which led to discovery of the North West Passage, Parry himself wrote letters testifying to the excellence of the preserved foods. The “tins” used by Captain Parry were far removed from the cans of today. They were made from a tinplate which comprised wrought iron sheet coated by hot dipping with layers of tin about 0.1 mm thick (considerably thicker than modern coatings).
The cylindrical can body was made from a rectangular tinplate sheet, the seamed joint being secured by soldering on the inside surface of the can. The lower end of the can consisted of a flanged tinplate disc and this was secured to the body by soldering it to the flange around the bottom edge. The top was soldered in place after solid food had been inserted and the liquid contents were added through a hole about 25 mm in diameter which was left in the centre of this lid. Finally, a small tinplate disc was soldered over this hole, to close the can completely. Opening these early cans required a chisel and some degree of strength; various patent closures and methods of opening them (the first can openers) were devised over the ensuing years. These first cans were expensive, since a skilled craftsman could only make 5 or 6 cans per hour.
With the enormous expansion of the American canning industry in the second half of the nineteenth century, developments, both in can design and rate of production, came rapidly. Whilst William Underwood was credited with making the first can sold in America in 1819, it was Gail Borden who was largely responsible for the wide acceptance of the can as a food container in the 1850s. He introduced canned condensed milk in 1853 and this was responsible for a significant lowering of the infant mortality figures, particularly in areas where fresh milk was not readily available, and helped to make the American consumer see the can as a safe, healthy preserver of food. After 1860, the art of canning was well on the way to becoming the science that it is today.
A major development was the introduction in the 1890s, of the first complete mechanised system for making cans, starting from sheets of tinplate and producing up to 6000 cans per hour. Up until the early part of the twentieth century the side seam solder had always been applied to the inside surface of the can. However, at this time, the “sanitary” can was developed, so called because the solder was now only applied to the external surface and the end was fixed by a mechanical double seam.
Whilst the can makers were developing their techniques, materials were also evolving. Between 1875 and 1885 steel gradually replaced iron as the basic material for tinplate. From then until 1929, there was a slow but steady evolution in the procedure for making tinplate. In 1929 cold reduced steel was introduced, thereby providing a more uniform and higher quality product. The importance was realised of controlling the chemical composition of the steel. When electroplating was introduced by a German chemist in the 1930s as a means of applying the tin coating, it represented a major advance in the technology of tinplate, but it was not widely adopted until 1942, when wartime shortages forced its acceptance, as a means of conserving tin.
Whilst the can makers were developing their techniques, materials were also evolving. Between 1875 and 1885 steel gradually replaced iron as the basic material for tinplate. From then until 1929, there was a slow but steady evolution in the procedure for making tinplate. In 1929 cold reduced steel was introduced, thereby providing a more uniform and higher quality product. The importance was realised of controlling the chemical composition of the steel. When electroplating was introduced by a German chemist in the 1930s as a means of applying the tin coating, it represented a major advance in the technology of tinplate, but it was not widely adopted until 1942, when wartime shortages forced its acceptance, as a means of conserving tin.
A significant new market for the can had become apparent after 1935 when, following the development of suitable internal coatings, the first beer cans were test marketed.
The tinplate can was further improved in the decade and a half following World War II. Line speed was increased to over 500 cans per minute for each soldering bodymaker and this was accompanied by an increase in quality and reliability. The first semi-automatic side-seam welding machine for can bodies was manufactured in 1959, but it was not until 1975 that the first three-piece food and beverage can bodies were capable of being continuously welded at high speeds.
Organic coatings, which had already been introduced to increase the resistance of the can to certain aggressive products, were vastly improved by the introduction of acrylics, vinyls, epoxies and phenolics. The introduction of an aluminium “easy- open” end in 1962 was highly significant in improving the convenience aspect and led to increasing sales of beverage cans. The process of drawing and ironing two-piece cans was perfected in 1963, initially in aluminium and, by the early 1970s, in tinplate also.
The lighter weight, thin walled, D&I cans offered many economic advantages. The aerosol container, first introduced commercially in the 1940s, has represented another major outlet for tinplate, where today it is made by both three-piece welding and two-piece D&I techniques.Since 1970, canmaking technology has been transformed by the continual development of the modern techniques of two-piece and three-piece manufacturing. These are leading to a more economical and cost effective use of materials and consequent reduction in environmental impact.
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