Tinning - AbsoluteAstronomy.com

Tinning is the process of thinly coating sheets of wrought iron

Wrought iron

thumb|The [[Eiffel tower]] is constructed from [[puddle iron]], a form of wrought ironWrought iron is an iron alloy with a very low carbon...

or steel

Steel

Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

with tin

Tin

Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4...

, and the resulting product is known as tinplate. It is most often used to prevent rust

Rust

Rust is a general term for a series of iron oxides. In colloquial usage, the term is applied to red oxides, formed by the reaction of iron and oxygen in the presence of water or air moisture...

.

While once more widely used, the primary use of tinplate now is the manufacture of tin can

Tin can

A tin can, tin , steel can, or a can, is a sealed container for the distribution or storage of goods, composed of thin metal. Many cans require opening by cutting the "end" open; others have removable covers. Cans hold diverse contents: foods, beverages, oil, chemicals, etc."Tin" cans are made...

s. Formerly, tinplate was used for cheap pots, pans and other holloware

Holloware

Holloware is a term that refers to table service items such as sugar bowls, creamers, coffee pots, teapots, soup tureens, hot food covers, water pitchers, platters, butter pat plates and other metal items that went with the china on a table. It does not include flatware. Holloware was constructed...

. 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

Bessemer process

The Bessemer process was the first inexpensive industrial process for the mass-production of steel from molten pig iron. The process is named after its inventor, Henry Bessemer, who took out a patent on the process in 1855. The process was independently discovered in 1851 by William Kelly...

steel or open-hearth. Formerly iron

Wrought iron

thumb|The [[Eiffel tower]] is constructed from [[puddle iron]], a form of wrought ironWrought iron is an iron alloy with a very low carbon...

was used, and was of two grades, coke

Coke (fuel)

Coke is the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal. Cokes from coal are grey, hard, and porous. While coke can be formed naturally, the commonly used form is man-made.- History :...

iron and charcoal

Charcoal

Charcoal is the dark grey residue consisting of carbon, and any remaining ash, obtained by removing water and other volatile constituents from animal and vegetation substances. Charcoal is usually produced by slow pyrolysis, the heating of wood or other substances in the absence of oxygen...

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 can

Tin can

s in which preserved meat

Meat

Meat is animal flesh that is used as food. Most often, this means the skeletal muscle and associated fat and other tissues, but it may also describe other edible tissues such as organs and offal...

, fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

, fruit

Fruit

In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...

, biscuit

Biscuit

A biscuit is a baked, edible, and commonly flour-based product. The term is used to apply to two distinctly different products in North America and the Commonwealth Nations....

s, cigarette

Cigarette

A cigarette is a small roll of finely cut tobacco leaves wrapped in a cylinder of thin paper for smoking. The cigarette is ignited at one end and allowed to smoulder; its smoke is inhaled from the other end, which is held in or to the mouth and in some cases a cigarette holder may be used as well...

s and numerous other products are packed, and also for the household utensils of various kinds made by the tinsmith

Tinsmith

A tinsmith, or tinner or tinker or tinplate worker, is a person who makes and repairs things made of light-coloured metal, particularly tinware...

History

The practice of tinning ironware to protect it against rust is an ancient one. This may have been the work of the whitesmith

Whitesmith

A whitesmith is a person who works with "white" or light-coloured metals such as tin and pewter. While blacksmiths work mostly with hot metal, whitesmiths do the majority of their work on cold metal .The term is also applied to metalworkers who do only finishing work – such as filing or polishing –...

. This was done after the article was fabricated, whereas tinplate was tinned before fabrication.

The manufacture of tinplate was long a monopoly

Monopoly

A monopoly exists when a specific person or enterprise is the only supplier of a particular commodity...

of Bohemia

Bohemia

Bohemia is a historical region in central Europe, occupying the western two-thirds of the traditional Czech Lands. It is located in the contemporary Czech Republic with its capital in Prague...

, but about 1620 the industry spread to Saxony

Saxony

The Free State of Saxony is a landlocked state of Germany, contingent with Brandenburg, Saxony Anhalt, Thuringia, Bavaria, the Czech Republic and Poland. It is the tenth-largest German state in area, with of Germany's sixteen states....

. 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.

Andrew Yarranton

Andrew Yarranton

Andrew Yarranton was an important English engineer in the 17th century who was responsible for making several rivers into navigable waterways.-Biography:...

, an English engineer

Engineer

An engineer is a professional practitioner of engineering, concerned with applying scientific knowledge, mathematics and ingenuity to develop solutions for technical problems. Engineers design materials, structures, machines and systems while considering the limitations imposed by practicality,...

and agriculturist, and Ambrose Crowley (a Stourbridge blacksmith and father of the more famous Sir Ambrose) were commissioned to go to Saxony and if possible discover the methods employed. They visited Dresden in 1667 and found out how it was made. In doing so, they were sponsored by various local ironmaster

Ironmaster

An ironmaster is the manager – and usually owner – of a forge or blast furnace for the processing of iron. It is a term mainly associated with the period of the Industrial Revolution, especially in Great Britain....

s and people connected with the project to make the river Stour

River Stour, Worcestershire

The Stour is a river flowing through the counties of Worcestershire, the West Midlands and Staffordshire in the West Midlands region of England. The Stour is a major tributary of the River Severn, and it is about in length...

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 the ironmasters Philip Foley

Philip Foley

Philip Foley was the youngest of the three surviving sons of the British ironmaster Thomas Foley . His father transferred to him in 1668 and 1669 all his ironworks in the Midlands for £60,000...

and Joshua Newborough (two of the sponsors) in 1670 erecting a new mill, Wolverley

Wolverley

Wolverley is a village, and with Cookley together, a civil parish in the Wyre Forest District of Worcestershire, England. It is located a few miles to the north west of Kidderminster, near the town of Bewdley, and the villages of Kinver and Cookley...

Lower Mill (or forge). This contained three shops, one being a slitting mill

Slitting mill

The slitting mill was a watermill for slitting bars of iron into rods. The rods then were passed to nailers who made the rods into nails, by giving them a point and head....

(which would serve as a rolling mill), and the others were forges. In 1678 one of these was making frying pan

Frying pan

A frying pan, frypan, or skillet is a flat-bottomed pan used for frying, searing, and browning foods. It is typically in diameter with relatively low sides that flare outwards, a long handle, and no lid. Larger pans may have a small grab handle opposite the main handle...

s and the other drawing out bloom

Bloom

Bloom or blooming may refer to:-Science and nature:* Bloom, one or more flowers on a flowering plant* Algal bloom, a rapid increase or accumulation in the population of algae in an aquatic system...

s made in finery forge

Finery forge

Iron tapped from the blast furnace is pig iron, and contains significant amounts of carbon and silicon. To produce malleable wrought iron, it needs to undergo a further process. In the early modern period, this was carried out in a finery forge....

s 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

Patent

A patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....

granted to him and Dud Dudley in 1662. Yarranton described the patent as "trumped up".

The slitter at Wolverley

Wolverley

was Thomas Cooke. Another Thomas Cooke, perhaps his son, moved to Pontypool

Pontypool

Pontypool is a town of approximately 36,000 people in the county borough of Torfaen, within the historic boundaries of Monmouthshire in South Wales....

and worked there for John Hanbury (1664-1734). According to Edward Lhuyd

Edward Lhuyd

Edward Lhuyd was a Welsh naturalist, botanist, linguist, geographer and antiquary. He is also known by the Latinized form of his name, Eduardus Luidius....

, by 1697, John Hanbury had a rolling mill at Pontypool

Pontypool

Pontypool is a town of approximately 36,000 people in the county borough of Torfaen, within the historic boundaries of Monmouthshire in South Wales....

for making "Pontypoole Plates" machine. 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 hammer

Hammer

A hammer is a tool meant to deliver an impact to an object. The most common uses are for driving nails, fitting parts, forging metal and breaking up objects. Hammers are often designed for a specific purpose, and vary widely in their shape and structure. The usual features are a handle and a head,...

ing, and in consequence the English tinplate became recognized as superior to the German

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

.

Tinplate first begins to appear in the Gloucester Port Books (which record trade passing through Gloucester

Gloucester

Gloucester is a city, district and county town of Gloucestershire in the South West region of England. Gloucester lies close to the Welsh border, and on the River Severn, approximately north-east of Bristol, and south-southwest of Birmingham....

, mostly from ports in the Bristol Channel

Bristol Channel

The Bristol Channel is a major inlet in the island of Great Britain, separating South Wales from Devon and Somerset in South West England. It extends from the lower estuary of the River Severn to the North Atlantic Ocean...

in 1725. The tinplate was shipped from Newport, Monmouthshire. This immediately follows the first appearance (in French

French language

French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...

of Réaumur

René Antoine Ferchault de Réaumur

René Antoine Ferchault de Réaumur was a French scientist who contributed to many different fields, especially the study of insects.-Life:Réaumur was born in a prominent La Rochelle family and educated in Paris...

'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 1805, 80,000 boxes were made and 50,000 exported. The industry continued to spread steadily in England and especially Wales

Wales

Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...

, and after 1834 its expansion was rapid, Great Britain

Great Britain

Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...

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 1848 it was 420,000 boxes, in 1860 it reached 1,700,000 boxes. But subsequently the advance was rapid, and the production reached about 2,236,000 lb in 1891. One of the greatest markets was the United States of America, but that market was cut off in 1891, when the McKinley tariff

McKinley Tariff

The Tariff Act of 1890, commonly called the McKinley Tariff, was an act framed by Representative William McKinley that became law on October 1, 1890. The tariff raised the average duty on imports to almost fifty percent, an act designed to protect domestic industries from foreign competition...

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.

In 1891, the United States made 11,000 tons of tinplate and imported 325,100 tons, but in 1899, 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., had by 1900 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 1907 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 1937, 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

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 in about the 1960s.

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

Ironworks

An ironworks or iron works is a building or site where iron is smelted and where heavy iron and/or steel products are made. The term is both singular and plural, i.e...

or steel works. The tin bar could be wrought iron

Wrought iron

thumb|The [[Eiffel tower]] is constructed from [[puddle iron]], a form of wrought ironWrought iron is an iron alloy with a very low carbon...

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 by 20 in (355.6 by 508 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. Continuing the example, if the starting tin bar is 20 by 56 in (508 by 1,422.4 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

Red heat

The practice of using colours to determine the temperature of a piece of ferrous metal comes from blacksmithing. Long before thermometers were widely available it was necessary to know what state the metal was in for heat treating it and the only way to do this was to heat it up to a colour which...

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.

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.

At this point, the plates are covered in scale

Fouling

Fouling refers to the accumulation of unwanted material on solid surfaces, most often in an aquatic environment. The fouling material can consist of either living organisms or a non-living substance...

and therefore must be pickled. This involves dipping the plates in sufuric 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

Stamping (metalworking)

Stamping includes a variety of sheet-metal forming manufacturing processes, such as punching using a machine press or stamping press, blanking, embossing, bending, flanging, and coining. This could be a single stage operation where every stroke of the press produce the desired form on the sheet...

and enameling purposes.

After this, the plates are still rough and not straight, so they are cold rolled several times. The rolling lengths 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

Sulfuric acid

Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...

. Finally they are rinsed and stored in water until ready to be tinned.

The tinning set consists of at least one pot of molten tin, with a zinc chloride

Zinc chloride

Zinc chloride is the name of chemical compound with the formula ZnCl2 and its hydrates. Zinc chlorides, of which nine crystalline forms are known, are colorless or white, and are highly soluble in water. ZnCl2 itself is hygroscopic and even deliquescent. Samples should therefore be protected from...

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 any excess tin off. 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

Bran

Bran is the hard outer layer of grain and consists of combined aleurone and pericarp. Along with germ, it is an integral part of whole grains, and is often produced as a by-product of milling in the production of refined grains. When bran is removed from grains, the grains lose a portion of their...

and dusted clean.

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. However 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 1740) 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.

The strip mill

Early hot rolling strip mills did not produce strip suitable for tinning, but in 1929 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.

Tinning processes

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

Electroplating

Electroplating is a plating process in which metal ions in a solution are moved by an electric field to coat an electrode. The process uses electrical current to reduce cations of a desired material from a solution and coat a conductive object with a thin layer of the material, such as a metal...

Hot-dipping

Tinplate made via hot-dipped tin plating is made by cold rolling steel or iron, pickling

Pickling (metal)

Tarnision is a metal surface treatment used to remove impurities, such as stains, inorganic contaminants, rust or scale from ferrous metals, copper, and aluminum alloys. A solution called Tarnision liquor, which contains strong acids, is used to remove the surface impurities...

or remove any scale

Fouling

, annealing

Annealing (metallurgy)

Annealing, in metallurgy and materials science, is a heat treatment wherein a material is altered, causing changes in its properties such as strength and hardness. It is a process that produces conditions by heating to above the recrystallization temperature, maintaining a suitable temperature, and...

to remove any strain hardening, and then coating it with a thin layer of tin

Tin

. Originally this was done by producing individual or small packs of plates, which became known as the pack mill process. In the late 1920s 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

Cathode

A cathode is an electrode through which electric current flows out of a polarized electrical device. Mnemonic: CCD .Cathode polarity is not always negative...

(negative) of the circuit while an electrode typically of the same metal to be plated forms the anode

Anode

An anode is an electrode through which electric current flows into a polarized electrical device. Mnemonic: ACID ....

(positive). When an electrical current is passed through the circuit, metal ion

Ion

An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...

s in the solution are attracted to the item.

Alternatives

Terne-plate is a similar product to tinplate, but the bath is not of tin, but of tin and lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

mixed, the latter metal constituting from 7.59% of the whole. The name derives from 'terne' - meaning dull or tarnish
Tarnish
Tarnish is a thin layer of corrosion that forms over copper, brass, silver, aluminum, and other similar metals as their outermost layer undergoes a chemical reaction. Tarnish does not always result from the sole effects of oxygen in the air. For example, silver needs hydrogen sulfide to tarnish; it...

. Terne-plates began to be produced in England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

about the middle of the 19th century, and are widely employed in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

for roofing purposes.
For many purposes, tinplate has been replaced by galvanised
Galvanization
Galvanization is the process of applying a protective zinc coating to steel or iron, in order to prevent rusting. The term is derived from the name of Italian scientist Luigi Galvani....

(zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...

-coated) vessels, though not for cooking as zinc is toxic. Zinc protects iron electrolytically
Electrolysis
In chemistry and manufacturing, electrolysis is a method of using a direct electric current to drive an otherwise non-spontaneous chemical reaction...

, that is, the zinc will oxidize and turn to a white powder to preserve the iron, whereas tin will only protect the iron if the tin-surface remains unbroken.

History

The pack mill process

The strip mill

Tinning processes

Hot-dipping

Electroplating

Alternatives

See also

Further reading