Tinning

Tinning is the process of thinly coating sheets of wrought iron or steel with tin, and the resulting product is known as tinplate. The term is also widely used for the different process of coating a metal with solder before soldering.[1]

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It is most often used to prevent rust, but is also commonly applied to the ends of stranded wire used as electrical conductors to prevent oxidation (which increases electrical resistance), and to keep them from fraying or unraveling when used in various wire connectors like twist-ons, binding posts, or terminal blocks, where stray strands can cause a short circuit.

While once more widely used, the primary use of tinplate now is the manufacture of tin cans. Formerly, tinplate was[clarification needed] used for cheap pots, pans, and other holloware. This kind of holloware was also known as tinware and the people who made it were tinplate workers.

The untinned sheets employed in the manufacture are known as black plates. They are now made of steel, either Bessemer steel or open-hearth. Formerly iron was used, and was of two grades, coke iron and charcoal iron; the latter, being the better, received a heavier coating of tin, and this circumstance is the origin of the terms coke plates and charcoal plates by which the quality of tinplate is still designated, although iron is no longer used. Tinplate was consumed in enormous quantities for the manufacture of the tin cans in which preserved meat, fish, fruit, biscuits, cigarettes, and numerous other products are packed, and also for the household utensils of various kinds made by the tinsmith.

History

The practice of tinning ironware to protect it against rust is an ancient one. According to Pliny the Elder tinning was invented by the Gallic Bituriges tribe (based near modern Bourges), who boiled copper objects in a tin solution in order to make them look as if they were made from silver.[3] The first detailed account of the process appears in Zosimus of Panopolis, Book 6.62, part of a work on alchemy written in Roman Egypt around 300 AD. Aside from an attestation in 14th century England, the process is not attested again in Europe until the description in Lazarus Ercker's Das Kleine Probierbuch ()

The manufacture of tinplate was long a monopoly of Bohemia, but in about the year the industry spread to Saxony. Tinplate was apparently produced in the s at a mill of (or under the patronage of) the Earl of Southampton, but it is not clear how long this continued.

Andrew Yarranton, an English engineer and agriculturist, and Ambrose Crowley (a Stourbridge blacksmith and father of the more famous Sir Ambrose Crowley III) were commissioned to go to Saxony and if possible discover the methods employed. They visited Dresden in and found out how it was made. In doing so, they were sponsored by various local ironmasters and people connected with the project to make the River Stour navigable. In Saxony, the plates were forged, but when they conducted experiments on their return to England, they tried rolling the iron. This led to two of the sponsors, the ironmasters Philip Foley and Joshua Newborough, erecting a new mill, Wolverley Lower Mill (or forge), in . This contained three shops: one being a slitting mill, which would serve as a rolling mill, the others being forges. In one of these was making frying pans and the other drawing out blooms made in finery forges elsewhere. It is likely that the intention was to roll the plates and then finish them under a hammer, but the plan was frustrated by one William Chamberlaine renewing a patent granted to him and Dud Dudley in . Yarranton described the patent as "trumped up".[5][6]

The slitter at Wolverley was Thomas Cooke. Another Thomas Cooke, perhaps his son, moved to Pontypool and worked there for John Hanbury (&#;).[7] According to Edward Lhuyd, by , John Hanbury had a rolling mill at Pontypool for making "Pontypoole Plates" machine.[8][9] This has been claimed as a tinplate works, but it was almost certainly only producing (untinned) blackplate. However, this method of rolling iron plates by means of cylinders, enabled more uniform black plates to be produced than was possible with the old plan of hammering, and in consequence the English tinplate became recognised as superior to the German.

Tinplate first begins to appear in the Gloucester Port Books (which record trade passing through Gloucester, mostly from ports in the Bristol Channel) in . The tinplate was shipped from Newport, Monmouthshire.[10] This immediately follows the first appearance (in French) of Réaumur's Principes de l'art de fer-blanc, and prior to a report of it being published in England.

Further mills followed a few years later, initially in many ironmaking regions in England and Wales, but later mainly in south Wales. In , 80,000 boxes were made and 50,000 exported. The industry continued to spread steadily in England and especially Wales, and after its expansion was rapid, Great Britain becoming the chief source of the world's supply. In that year her total production was 180,000 boxes of 108 lb each (around 50 kg, in America a box is 100 lb), in it was 420,000 boxes, in it reached 1,700,000 boxes. But subsequently the advance was rapid, and the production reached about 2,236,000 lb in . One of the greatest markets was the United States of America, but that market was cut off in , when the McKinley tariff was enacted there. This caused a great retrenchment in the British industry and the emigration to America of many of those who could no longer be employed in the surviving tinplate works.[citation needed]

In , the United States made 11,000 tons of tinplate and imported 325,100 tons, but in , it made 360,900 tons, importing only 63,500 tons (mostly for re-export). British exports were further hindered by the Dingley tariff, which removed the advantage of Welsh plate on America's Pacific coast,[11] had by increased to more than 849,000,000 lb, of which over 141,000,000 lb were terne-plates. The total imports in that year were only 135,264,881 lb. In later years, again, there was a decline in the American production, and in only 20% of the American tinplate mills were at work, while the British production reached 14 million boxes.

Despite this blow, the industry continued, but on a smaller scale. Nevertheless, there were still 518 mills in operation in , including 224 belonging to Richard Thomas & Co. However 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 s. Strip mills rendered the old pack mills obsolete and the last of them closed in about the s.

Plate production methods

The pack mill process

The pack mill process begins with a tin bar, which is a drawn flat bar that was usually purchased from an ironworks or steel works. The tin bar could be wrought iron or mild steel. The cross-section of the bar needed to be accurate in size as this dictates the length and thickness of the final plates. The bar was cut to the correct length to make the desired size plate. For instance, if a 14 in × 20 in (360 mm × 510 mm) plate is desired the tin bar is cut to a length and width that is divisible by 14 and 20. The bar is then rolled and doubled over, with the number of times being doubled over dependent on how large the tin bar is and what the final thickness is. If the starting tin bar is 20 in × 56 in (510 mm × 1,420 mm) then it must be at least finished on the fours, or doubled over twice, and if a thin gauge is required then it may be finished on the eights, or doubled over three times. The tin bar is then heated to a dull red heat and passed five or six times through the roughing rolls. Between each pass the plate is passed over (or round) the rolls, and the gap between the rolls is narrowed by means of a screw. The plate is then reheated and run through the finishing rolls.[12]

If the plate is not finished on singles, or without doubling the plate over, it is doubled over in a squeezer. The squeezer was like a table where one half of the surface folds over on top of the other and a press flattens the doubled over plate so the rolled end will fit in the rollers. It is then reheated for another set of rolling. This is repeated until the desired geometry is reached. Note that if the plate needs to be doubled over more than once the rolled end is sheared off. The pack is then allowed to cool. When cool, the pack is sheared slightly undersized from the final dimensions and the plates separated by openers.[13]

At this point, the plates are covered in scale and must be pickled. This involves dipping the plates in sulfuric acid for five minutes. The pickling turns the scales into a greenish-black slime which is removed via annealing. The plates are annealed for approximately 10 hours and then allowed to slowly cool. At this point the plates are known as pickled and annealed black plates. These plates were commonly sold for stamping and enameling purposes.[14]

After this, the plates are rough and not straight, so they are cold rolled several times. The rolling lengthens the plates to their final dimension. They are then annealed again to remove any strain hardening. These plates are called black plate pickled, cold rolled, and close annealed (black plate p. cr. and ca.). To attain perfect cleanliness the plates are pickled again in a weak sulfuric acid. Finally they are rinsed and stored in water until ready to be tinned.[15]

The tinning set consists of at least one pot of molten tin, with a zinc chloride flux on top, and a grease pot. The flux dries the plate and prepares it for the tin to adhere. If a second tin pot is used, called the wash pot, it contains tin at a lower temperature. This is followed by the grease pot, which contains oil and a tinning machine. The tinning machine has two small rollers that are spring-loaded together so that when the tinned plate is inserted the rolls squeeze off any excess tin. The springs on the tinning machine can be set to different forces to give different thicknesses of tin. Finally, the oil is cleaned off with fine bran and dusted clean.[16][17]

What is described here is the process as employed during the 20th century. The process grew somewhat in complexity over time, as it was found that the inclusion of additional procedures improved quality. The practice of hot rolling and then cold rolling evidently goes back to the early days, as the Knight family's tinplate works had (from its foundation in about ) two rolling mills, one at Bringewood (west of Ludlow) which made blackplate, and the other the tin mill at Mitton (now part of Stourport, evidently for the later stages.[18][page needed]

The strip mill

Early hot rolling strip mills did not produce strip suitable for tinning, but in cold rolling began to be used to reduce the gauge further, which made tinning achievable. The plate was then tinned using the process outlined above.[citation needed]

Tinning processes

There are two processes for the tinning of the black plates: hot-dipping and electroplating.

Hot-dipping

Hot tin-dipping is the process of immersing a part into a bath of pure molten tin at a temperature greater than 450 °F or 232 °C.

Tinplate made via hot-dipped tin plating is made by cold rolling steel or iron, pickling to remove any scale, annealing to remove any strain hardening, and then coating it with a thin layer of tin. Originally this was done by producing individual or small packs of plates, which became known as the pack mill process. In the late s strip mills began to replace pack mills, because they could produce the raw plates in larger quantities and more economically.

Electroplating

In electroplating, the item to be coated is placed into a container containing a solution of one or more tin salts. The item is connected to an electrical circuit, forming the cathode (negative) of the circuit while an electrode typically of the same metal to be plated forms the anode (positive). When an electric current is passed through the circuit, metal ions in the solution are attracted to the item. To produce a smooth, shiny surface, the electroplated sheet is then briefly heated above the melting point of tin. Most of the tin-plated steel made today is then further electroplated with a very thin layer of chromium to prevent dulling of the surface from oxidation of the tin.

Alternatives

• Terne-plate is a similar product to tinplate, but the bath is not of tin, but of tin and lead mixed, the latter metal constituting from 7.59% of the whole. The name derives from "terne", meaning dull or tarnish. Terne-plates began to be produced in England about the middle of the 19th century, and became widely employed in the United States for roofing purposes. Other applications included fuel tanks and gas meters. The last Terne-plate mill in Brockmoor, West Midlands in the UK was closed in .[1]
• For many purposes, tinplate has been replaced by galvanised (zinc-coated) vessels - though not for cooking, as zinc can be toxic. A Zinc protects iron electrolytically, that is, the zinc will oxidise and turn to a white powder to preserve the iron, whereas tin will only protect the iron if the tin-surface remains unbroken, as it electrolytically cannibalises unprotected iron to preserve itself.

See also

• Blackplate
• Kalai (process), a form of tinning practiced in India
• Plating for other processes for plating metals
• Sherardizing
• Tinsmith
• Tinware
• Black oxide

References

Bibliography

• Brown, P. J. (), "Andrew Yarranton and the British tinplate industry", Historical Metallurgy, vol. 22, no. 1, pp. 42&#;8
• This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (). "Tin-plate and Terne-plate". Encyclopædia Britannica. Vol. 26 (11th ed.). Cambridge University Press. p. .
• King, P. W. (), "Wolverley Lower Mill and the beginnings of the tinplate industry", Historical Metallurgy, vol. 22, no. 2, pp. 104&#;113
• Minchinton, W. W. (), The British tinplate industry: a history, Clarendon Press, Oxford
• Tregoning, W. H. (), "Proceedings - Institution of Mechanical Engineers, Parts 3-5", in Institution of Mechanical Engineers (Great Britain) (ed.), The manufacture of tin-plate, Institution by Mechanical Engineering Publications Ltd., pp. &#;
• Welter, J.-M. (). "Contact tinning: A millennia-old plating technology". Archaeometry. 61 (4): 906&#;920. doi:10./arcm.. S2CID .

Further reading

1. F. W. Gibbs, 'The rise of the tinplate industry' Annals of Science 6 (), 390ff; 7(1) (), 25ff; 43ff; 113ff.

Tin- the bigger picture

At Tinplate, we like to see ourselves as the latest chapter in a long and exciting history! We may specialise in beautiful packaging and bespoke tins, but we&#;re part of a much bigger &#;tin story&#;. Here&#;s a snapshot of what makes tin so important&#;

What can tin do?

Tin has a wide range of uses in manufacturing, and can be found in consumer goods, packaging, construction and transportation. Tin compound is even used in some toothpastes! But here are the main areas where tin comes into its own&#;:

Soldering

Tin can be used for soldering &#; connecting two pieces of different metal together. Nearly 45% of tin consumed globally is used in the electrical and electronics industry. The conductive joints in almost every electronic product are made from tin.

Tinplate

Tin coating provides essential rusting protection, which is why it works well for preserving food. However, tinplate &#; which accounts for about 16% of tin consumption &#; is now used to package a multitude of products, and make them look extremely attractive to a customers.

Chemicals

Tin chemicals are also used in a huge number of everyday applications, most commonly as organic tin chemicals in PVC for construction products such as doors and windows. This helps to stop degradation in heat and sunlight.

Brass and bronze

The use of tin as a plating material dates to the time of the Roman Empire, when copper vessels were coated with tin to keep them looking bright. Take a look at B.C. on the Tinplate interactive timeline for a video on how you can make copper at home.

Float glass

Float glass is what we find in modern windows, and its uniform flatness is made possible by a process that relies on tin. Check out on the Tinplate interactive timeline to see how float glass is made.

Tin Mining Through the Ages

Tin down the ages: who discovered tin and when?

Because it&#;s so useful in so many ways, it&#;s no surprise that tin has had a lively history. Here are some key dates:

The company is the world’s best Electrolytic Tinplate supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.

B.C.

The earliest use of tin was around years B.C. Metalworkers in what is now Turkey learned to add tin to mildly soft copper to form a much stronger bronze. From this bronze, harder tools and better weaponry were made. This is what caused the shift from The Copper Age to The Bronze Age, which lasted for two millennia.

B.C.

The Bronze Age lasted 2,000 years. True bronze is a combination of 10% tin and 90% copper, and both materials were readily available in Britain throughout the period.  But before its entry into Britain, the Bronze Age was in full swing in Europe. Some of the finest bronze weapons were made by the Mycenaeans, who came from Southern Russia at around B.C., and settled in the lowlands of Greece. There they began to trade with the Minoans.

B.C. to B.C.

Thailand are now producing bronze. There is a bronze foundry established in Bangkok, Thailand since . They are dedicated to manufacturing the highest quality bronze products for more than 50 years. Below is one of their masterpieces:

B.C. to B.C.

The earliest tin objects known to have been found are a ring and a pilgrim bottle, from Egyptian graves of the Eighteenth Dynasty ( B.C. to B.C.). The earliest reference to tin is in the Harris Papyrus, an Egyptian document of the Twentieth Dynasty ( B.C. to B.C.). We then come across tin in the writings of Homer (ninth cent. B.C), before another Egyptian reference in the Twenty-Fifth Dynasty (712 B.C. to 663 B.C.). There is also a reference to tin in the Old Testament, in Numbers.

B.C.

When extensive tin deposits were found in England, traders brought the precious metal to countries in the Mediterranean area, but kept the source a secret. It wasn&#;t until 310 B.C. that the Greek explorer Pytheas discovered the location of the mines near what is now Cornwall. Britain comes into prominence as a tin-producing country, and Cornwall, together with the west of Devon, was for centuries the most important tin-mining region of the world.

The date when the Cornish tin ore was first worked is a much disputed point, but it must have been before the Roman conquest of Britain, since British pre-Roman objects have been found in the ancient workings, and tin was used for certain British pre-Roman coinage. Even this, however, does not carry the mining very far back, since coinage was only introduced into Britain about 200 B.C.

310 B.C.

Much of the motivation for the Roman invasion of Britain in 43 A.D. was to control the tin trade. With their well-known efficiency and thoroughness, the Romans counted access to the British tin mines as one of the advantages of conquering the island. Julius Caesar knew of the importance of British tin when he invaded the island in 55 to 54 B.C. After the conquest of Britain during the reign of Claudius, the Romans were in control of most of the world&#;s supply of the metal.

&#;s

The use of tin as a plating material dates to the time of the Roman Empire, when copper vessels were coated with tin to keep them looking bright. Tinned iron vessels appeared in central Europe in the &#;s. In archaeologists uncovered a vessel off the Devon Coast, which is thought to date back to around 900 BC. You can find out more about the discovery here: Bronze Age shipwreck found off Devon coast

Tinplate has been commercially made in the UK since the late s, originally by dipping sheets of wrought iron, and later steel, into baths of molten tin. During World War II, electro-coating was introduced, allowing the continuous application of tin to both sides of the metal simultaneously; tin could thus be applied to wide coils of steel, which could be unwound, coated and then rewound.

A hundred years ago there were 83 tinplate works, mostly in South Wales. Today, there is a single UK manufacturer, Tata Packaging Steel at the Trostre factory in Llanelli &#; though many businesses, such as Tinplate, make tin packaging products.

During the s, it became common practice to give a tin bonnet as a tenth-anniversary gift. Perhaps more significantly, in , Pierre Durand (of France) patented a method of preserving food in sealed tinplate cans. It then took many years of testing to perfect this new technique.

In , Isaac Babbitt of the United States invented an antifriction alloy, called Babbitt metal, which consisted of tin, antimony, and copper. It was mostly used in bearings, and greatly aided the development of high-speed machinery and transportation.

Pierre Durand&#;s method of preserving food in sealed tinplate cans was now being perfected. Tin coating on thinly rolled sheet steel provides resistance to corrosion. It is used to protect food, beverages or other products contained in the package, and to resist external factors such as heat processing steam/water systems. A polymer coating is sometimes added on the inside surface, to prevent chemical action and the possible transfer of taint between metal and product.

In the twenty-firs century, approximately 80,000 million cans are produced and filled across the world each year (JECFA, ; Blunden & Wallace, ).

In , an English company, Pilkington, transformed the glassmaking industry with the introduction of the float glass method for the continuous production of sheet glass. Float glass is a sheet of glass made by floating molten glass on a bed of molten metal (typically tin, although lead and various low melting point alloys were used in the past). This method gives the sheet uniform thickness and very flat surfaces.

More than 22 countries produce tin, but the six largest producers in were China (33%), Indonesia (32%), Peru (13%), Bolivia (7%), Brazil (4%), and DR Congo (2%). Significant quantities are also produced from smelters in Malaysia and Thailand.

As energy-saving measures become increasingly important to governments and consumers, there&#;s likely to be an increase in demand for tin in &#;green technologies&#;. For example, in the production of polyurethane foam thermal insulation, and in tin oxide coatings for low emissivity &#;e-glass&#;.

Tinplate Products and contemporary tin

Alongside all its practical advantages, tin has wonderful aesthetic appeal, too. It can make a product feel extra special, and offer a &#;vintage touch&#;. Perhaps that&#;s why tins &#; especially early twentieth-century designs &#; have become very desirable as collectables.

Many different types of company are now incorporating tin into their packaging, marketing and branding. Here is an example: Tincan Restaurant Serving Only Tinned Fish

Tinplate Products works closely with clients who want to express their reliability and creativity through a tried and tested medium.

After nearly years, it&#;s safe to say that tin isn&#;t just a fad!

Further Reading

About metals
Made How
Elemental Matter

Best Tin Packaging