In
printing
Printing is a process for mass reproducing text and images using a master form or template. The earliest non-paper products involving printing include cylinder seals and objects such as the Cyrus Cylinder and the Cylinders of Nabonidus. The ...
, type metal refers to the metal
alloy
An alloy is a mixture of chemical elements of which in most cases at least one is a metal, metallic element, although it is also sometimes used for mixtures of elements; herein only metallic alloys are described. Metallic alloys often have prop ...
s used in traditional
typefounding
Movable type (US English; moveable type in British English) is the system and technology of printing and typography that uses movable components to reproduce the elements of a document (usually individual alphanumeric characters or punctuation ...
and
hot metal typesetting
In printing and typography, hot metal typesetting (also called mechanical typesetting, hot lead typesetting, hot metal, and hot type) is a technology for typesetting text in letterpress printing. This method injects molten type metal into a mo ...
. Historically, type metal was an
alloy
An alloy is a mixture of chemical elements of which in most cases at least one is a metal, metallic element, although it is also sometimes used for mixtures of elements; herein only metallic alloys are described. Metallic alloys often have prop ...
of
lead
Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...
,
tin
Tin is a chemical element; it has symbol Sn () and atomic number 50. A silvery-colored metal, tin is soft enough to be cut with little force, and a bar of tin can be bent by hand with little effort. When bent, a bar of tin makes a sound, the ...
and
antimony
Antimony is a chemical element; it has chemical symbol, symbol Sb () and atomic number 51. A lustrous grey metal or metalloid, it is found in nature mainly as the sulfide mineral stibnite (). Antimony compounds have been known since ancient t ...
in different proportions depending on the application, be it individual character mechanical casting for hand setting, mechanical line casting or individual character mechanical typesetting and stereo plate casting. The proportions used are in the range: lead 50‒86%, antimony 11‒30% and tin 3‒20%. Antimony and tin are added to lead for durability while reducing the difference between the coefficients of expansion of the matrix and the alloy. Apart from durability, the general requirements for type-metal are that it should produce a true and sharp cast, and retain correct dimensions and form after cooling down. It should also be easy to cast, at reasonable low
melting temperature, iron should not dissolve in the molten metal, and mould and nozzles should stay clean and easy to maintain. Today, Monotype machines can utilize a wide range of different alloys. Mechanical linecasting equipment uses alloys that are close to
eutectic.
History
Although the knowledge of
casting
Casting is a manufacturing process in which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a casting, which is ejected or ...
soft metals in
mould
A mold () or mould () is one of the structures that certain fungi can form. The dust-like, colored appearance of molds is due to the formation of spores containing fungal secondary metabolites. The spores are the dispersal units of the fungi ...
s was well established before
Johannes Gutenberg
Johannes Gensfleisch zur Laden zum Gutenberg ( – 3 February 1468) was a German inventor and Artisan, craftsman who invented the movable type, movable-type printing press. Though movable type was already in use in East Asia, Gutenberg's inven ...
's time, his discovery of an alloy that was hard, durable, and would take a clear impression from the mould represents a fundamental aspect of his solution to the problem of
printing
Printing is a process for mass reproducing text and images using a master form or template. The earliest non-paper products involving printing include cylinder seals and objects such as the Cyrus Cylinder and the Cylinders of Nabonidus. The ...
with
movable type
Movable type (US English; moveable type in British English) is the system and technology of printing and typography that uses movable Sort (typesetting), components to reproduce the elements of a document (usually individual alphanumeric charac ...
. This alloy did not shrink as much as lead alone when cooled. Gutenberg's other contributions were the creation of inks that would adhere to metal type and a method of softening handmade printing paper so that it would take the impression well.
Required characteristics
Cheap, plentifully available as
galena
Galena, also called lead glance, is the natural mineral form of lead(II) sulfide (PbS). It is the most important ore of lead and an important source of silver.
Galena is one of the most abundant and widely distributed sulfide minerals. It crysta ...
and easily workable,
lead
Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...
has many of the ideal characteristics, but on its own it lacks the necessary hardness and does not make castings with sharp details because molten lead shrinks and sags when it cools to a solid.
After much experimentation it was found that adding
pewterer's
tin
Tin is a chemical element; it has symbol Sn () and atomic number 50. A silvery-colored metal, tin is soft enough to be cut with little force, and a bar of tin can be bent by hand with little effort. When bent, a bar of tin makes a sound, the ...
, obtained from
cassiterite
Cassiterite is a tin oxide mineral, SnO2. It is generally opaque, but it is translucent in thin crystals. Its luster and multiple crystal faces produce a desirable gem. Cassiterite was the chief tin ore throughout ancient history and remains ...
, improved the ability of the cast type to withstand the wear and tear of the printing process, making it tougher but not more brittle.
Despite patiently trying different proportions of both metals, solving the second part of the type metal problem proved very difficult without the addition of yet a third metal,
antimony
Antimony is a chemical element; it has chemical symbol, symbol Sb () and atomic number 51. A lustrous grey metal or metalloid, it is found in nature mainly as the sulfide mineral stibnite (). Antimony compounds have been known since ancient t ...
.
Alchemists had shown that when
stibnite
Stibnite, sometimes called antimonite, is a sulfide mineral, a mineral form of antimony trisulfide ( Sb2 S3). It is a soft, metallic grey crystalline solid with an orthorhombic space group. It is the most important source for the metalloid an ...
, an antimony sulfide
ore
Ore is natural rock or sediment that contains one or more valuable minerals, typically including metals, concentrated above background levels, and that is economically viable to mine and process. The grade of ore refers to the concentration ...
, was heated with scrap iron, metallic antimony was produced. The typefounder would typically introduce powdered stibnite and horseshoe nails into his crucible to melt lead, tin and antimony into type metal. Both the iron and the sulfides would be rejected in the process.
The addition of antimony conferred the much needed improvements in the properties of hardness, wear resistance and especially, the sharpness of reproduction of the
type design
Type design is the art and process of designing typefaces. This involves drawing each letterform using a consistent style. The basic concepts and design variables are described below.
A typeface differs from other modes of graphic production su ...
, given that it has the curious property of diminishing the shrinkage of the alloy upon solidification.
Composition of type metal
Type metal is an alloy of lead, tin and antimony in different proportions depending on the application, be it individual character mechanical casting for hand setting, mechanical line casting or individual character mechanical typesetting and stereo plate casting.
The proportions used are in the range: lead 50‒86%, antimony 11‒30% and tin 3‒20%. The basic characteristics of these metals are as follows:
Lead
Type metal is an alloy of lead (Pb). Pure lead is a relatively cheap metal, is soft thus easy to
work
Work may refer to:
* Work (human activity), intentional activity people perform to support themselves, others, or the community
** Manual labour, physical work done by humans
** House work, housework, or homemaking
** Working animal, an ani ...
, and it is easy to
cast
Cast may refer to:
Music
* Cast (band), an English alternative rock band
* Cast (Mexican band), a progressive Mexican rock band
* The Cast, a Scottish musical duo: Mairi Campbell and Dave Francis
* ''Cast'', a 2012 album by Trespassers William ...
since it melts at . However, it shrinks when it solidifies making
letters that are not sharp enough for printing. In addition pure lead letters will quickly deform during use; a direct result of the easy workability of lead.
Lead is exceptionally soft,
malleable
Ductility refers to the ability of a material to sustain significant plastic deformation before fracture. Plastic deformation is the permanent distortion of a material under applied stress, as opposed to elastic deformation, which is reversi ...
, and
ductile
Ductility refers to the ability of a material to sustain significant plastic deformation before fracture. Plastic deformation is the permanent distortion of a material under applied stress, as opposed to elastic deformation, which is reversi ...
but with little
tensile strength.
Lead oxide is a
poison
A poison is any chemical substance that is harmful or lethal to living organisms. The term is used in a wide range of scientific fields and industries, where it is often specifically defined. It may also be applied colloquially or figurati ...
, that primarily damages brain function. Metallic lead is more stable and less toxic than its oxidized form. Metallic lead cannot be absorbed through contact with skin, so may be handled, carefully, with far less risk than lead oxide.
Tin
Tin (Sn) promotes the fluidity of the molten alloy and makes the type tough, giving the alloy resistance to wear. It is harder, stiffer and tougher than lead.
Antimony
Antimony (Sb) is a
metalloid
A metalloid is a chemical element which has a preponderance of material property, properties in between, or that are a mixture of, those of metals and Nonmetal (chemistry), nonmetals. The word metalloid comes from the Latin language, Latin ''meta ...
element, which melts at . Antimony has a crystalline appearance while being both brittle and fusible.
When alloyed with lead to produce type metal, antimony gives it the hardness it needs to resist deformation during printing, and gives it sharper castings from the
mould
A mold () or mould () is one of the structures that certain fungi can form. The dust-like, colored appearance of molds is due to the formation of spores containing fungal secondary metabolites. The spores are the dispersal units of the fungi ...
to produce clear, easily read printed text on the page.
Typical type metal proportions
The actual compositions differed over time, different machines were adjusted to different alloys depending on the intended uses of the type. Printers had sometimes their own preferences about the quality of particular alloys. The Lanston
Monotype Corporation
Monotype Imaging Holdings Inc., founded as Lanston Monotype Machine Company in 1887 in Philadelphia by Tolbert Lanston, is an American (historically Anglo-American) company that specializes in digital typesetting and typeface design for use wit ...
in the
United Kingdom
The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...
had a whole range of alloys listed in their manuals.
Alloys for mechanical composition
Most
mechanical typesetting is divided basically into two different competing technologies: line casting (
Linotype and
Intertype) and single character casting (
Monotype
Monotyping is a type of printmaking made by drawing or painting on a smooth, non-absorbent surface. The surface, or matrix, was historically a copper etching plate, but in contemporary work it can vary from zinc or glass to acrylic glass. The ...
).
The manuals for the Monotype composition caster (1952 and later editions) mention at least five different alloys to be used for casting, depending the purpose of the type and the work to be done with it.
Although in general Monotype cast type characters can be visually identified as having a square
nick
Nick may refer to:
People and fictional characters
* Nick (given name), a list of people and fictional characters
* Désirée Nick, German actress and writer
Places
* Nick, Hungary, a village
* Nick, Warmian-Masurian Voivodeship, Poland, a ...
(as opposed to the round nicks used on foundry type), there is no easy way to identify the alloy aside from an expensive chemical
assay
An assay is an investigative (analytic) procedure in laboratory medicine, mining, pharmacology, environmental biology and molecular biology for qualitatively assessing or quantitatively measuring the presence, amount, or functional activity ...
in a laboratory.
Apart from this the two Monotype companies in the
United States
The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
and the
UK also made moulds with 'round' nicks. Typefounders and printers could and did order specially designed moulds to their own specifications: height, size, kind of nick, even the number of nicks could be changed.
Type produced with these special moulds can only be identified if the foundry or printer is known.
In Switzerland the company "Metallum Pratteln AG", in Basel had yet another list of type-metal alloys. If needed, any alloy according to customer specifications could be produced.
Dross
Regeneration-metal was melted into the
crucible
A crucible is a container in which metals or other substances may be melted or subjected to very high temperatures. Although crucibles have historically tended to be made out of clay, they can be made from any material that withstands temperat ...
to replace lost tin and antimony through the
dross
Dross is a mass of solid impurities floating on a molten metal or dispersed in the metal, such as in wrought iron. It forms on the surface of low- melting-point metals such as tin, lead, zinc or aluminium or alloys by oxidation of the metal. Fo ...
.
Every time type metal is remelted, tin and antimony
oxidise. These oxides form on the surface of the crucible and must be removed. After stirring the molten metal, grey powder forms on the surface, the dross, needing to be skimmed. Dross contains recoverable amounts of tin and antimony.
Dross must be processed at specialized companies, in order to extract the pure metals in conditions that would prevent environmental
pollution
Pollution is the introduction of contaminants into the natural environment that cause harm. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the component ...
and remain economically feasible.
Behaviour of bipolar alloys
Pure metal melts and solidifies in a simple manner at a specific temperature. This is not the case with alloys. There we find a range of temperatures with all kinds of different events. The melting temperature of all mixtures is considerably lower than the pure components.
Antimony/Lead mixture examples
The addition of a small amount of antimony (5% to 6%) to lead will significantly alter the alloy's behavior compared to pure lead: although the melting point of pure antimony is 630 °C, this mixture will be completely molten and a homogeneous fluid even at temperatures as low as 371 °C. Letting this mixture cool the alloy will remain liquid even through 355 °C, the melting point of pure lead. Once the temperature reaches 291 °C, lead
crystal
A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...
s will start to form, increasing the cohesion of the liquid alloy. At 252 °C, the mixture will start to fully solidify, during which the temperature will remain constant. Only when the mixture has fully solidified will the temperature start to decrease again.
Using a 10% antimony, 90% lead mixture delays lead crystal formation until approximately 260 °C.
Using a 12% antimony, 88% lead mixture prevents crystal formation entirely, becoming a ''
eutectic''. This alloy has a clear melting point, at 252 °C.
Increasing the antimony content beyond 12% will lead to predominantly antimony crystallization.
Tri-polar mixtures
Adding tin to this bipolar-system complicates the behaviour even further. Some tin enters into the eutectic. A mixture of 4% tin, 12% antimony, and 84% lead solidifies at 240 °C.
Depending from the metals in excess, compared with the eutectic, crystals are formed, depleting the liquid, until the eutectic 4/12 mixture is formed once more.
The 12/20 alloy contains many mixed crystals of tin and antimony, these crystals constitute the hardness of the alloy and the resistance against wear.
Raising the content of antimony cannot be done without adding some tin too. Because the fluidity of the mixture will dramatically diminish when the temperature goes down somewhere in the channels of the machine. Nozzles can be blocked by antimony crystals.
Metals used on typecasting machines
Eutectic alloys are used on Linotype-machines and Ludlow-casters to prevent blockage of the mould and to ensure continuous trouble-free casting.
Alloys used on Monotype machines tend to contain higher contents of tin, to obtain tougher character. All characters should be able to resist the pressure during printing. This meant an extra investment, but Monotype was an expensive system all the way.
Present usage of type metal
The fierce competition between the different mechanical typecasting systems like
Linotype and
Monotype
Monotyping is a type of printmaking made by drawing or painting on a smooth, non-absorbent surface. The surface, or matrix, was historically a copper etching plate, but in contemporary work it can vary from zinc or glass to acrylic glass. The ...
has given rise to some lasting fairy tales about typemetal. Linotype users looked down on Monotype and vice versa.
Monotype machines however can utilize a wide range of different alloys; maintaining a constant and a high production meant a strict standardization of the typemetal in the company, so as to reduce by all means any interruption of the production. Repeated assays were done at regular intervals to monitor the alloy used, since every time the metal is recycled, roughly half a per cent of tin content is lost through
oxidation
Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is ...
. These oxides are removed with the
dross
Dross is a mass of solid impurities floating on a molten metal or dispersed in the metal, such as in wrought iron. It forms on the surface of low- melting-point metals such as tin, lead, zinc or aluminium or alloys by oxidation of the metal. Fo ...
while cleaning the surface of the molten metal.
Nowadays this "battle" has lost its importance, at least for Monotype. The quality of the produced type is far more important. Alloys with a high-content of antimony, and subsequently a high content of tin, can be cast at a higher temperature, and at a lower speed and with more cooling at a Monotype composition or supercaster.
Although care was taken to avoid mixing different types of type metal in shops with different type casting systems, in actual practice this often occurred. Since a Monotype composition caster can cope with a variety of different metal alloys, occasional mixing of Linotype alloy with discarded typefounders alloy has proven its usefulness.
Contamination of type metals
Copper
Copper
Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...
has been used for hardening type metal; this metal easily forms mixed crystals with tin when the alloy cools down. These crystals will grow just below the exit opening of the nozzle in Monotype machines, resulting in a total blockage after some time. These nozzles are very difficult to clean, because the hard crystals will resist drilling.
Zinc
Brass
Brass is an alloy of copper and zinc, in proportions which can be varied to achieve different colours and mechanical, electrical, acoustic and chemical properties, but copper typically has the larger proportion, generally copper and zinc. I ...
spaces contain
zinc
Zinc is a chemical element; it has symbol Zn and atomic number 30. It is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic tabl ...
, which is extremely counterproductive in type metal. Even a tiny amount — less than 1% — will form a dusty surface on the molten metal surface that is difficult to remove. Characters cast from contaminated type metal such as this are of inferior quality, the solution being to discard and replace with fresh alloy.
Brass and zinc should therefore be removed before remelting. The same applies to
aluminium
Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...
, although this metal will float on top of the melt, and will be easily discovered and removed, before it is dissolved into the lead.
Magnesium
Magnesium
Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...
plates are very dangerous in molten lead, because this metal can easily burn and will ignite in the molten lead.
Iron
Iron
Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...
is hardly dissolved into type metal, although the molten metal is always in contact with the cast iron surface of the melting pot.
Historic references to type metals
Joseph Moxon, in his ''Mechanick Exercises'', mentions a mix of equal amounts of "antimony" and iron
nails.
The "antimony" here was in fact
stibnite
Stibnite, sometimes called antimonite, is a sulfide mineral, a mineral form of antimony trisulfide ( Sb2 S3). It is a soft, metallic grey crystalline solid with an orthorhombic space group. It is the most important source for the metalloid an ...
, antimony-sulfide (Sb
2S
3). The iron was burned away in this process, reducing the antimony and at the same time removing the unwanted
sulfur
Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...
. In this way ferro-sulfide was formed, that would evaporate with all the fumes.
The mixture of stibnite and nails was heated red hot in an open-air
furnace, until all is molten and finished. The resulting metal can contain up to 9% of iron. Further purification can be done by mixing the hot melt with kitchen-salt, NaCl. After this red hot lead from another melting pot is added and stirred thoroughly.
Some tin was added to the alloy for casting small characters and narrow spaces, to better fill narrow areas of the mould. The good properties of tin were well known. The use of tin was sometime minimized to save expenses.
Much of this toxic work was done by
child labour
Child labour is the exploitation of children through any form of work that interferes with their ability to attend regular school, or is mentally, physically, socially and morally harmful. Such exploitation is prohibited by legislation w ...
, a
labor force
In macroeconomics, the workforce or labour force is the sum of people either working (i.e., the employed) or looking for work (i.e., the unemployed):
\text = \text + \text
Those neither working in the marketplace nor looking for work are out ...
that includes
child
A child () is a human being between the stages of childbirth, birth and puberty, or between the Development of the human body, developmental period of infancy and puberty. The term may also refer to an unborn human being. In English-speaking ...
ren.
As a supposed
antidote
An antidote is a substance that can counteract a form of poisoning. The term ultimately derives from the Greek term φάρμακον ἀντίδοτον ''(pharmakon antidoton)'', "(medicine) given as a remedy". An older term in English which is ...
to the inhaled toxic metal fumes, the workers were given a mixture of
red wine
Red wine is a type of wine made from dark-colored grape varieties - (red grapes.) The color of the wine can range from intense violet, typical of young wines, through to brick red for mature wines and brown for older red wines. The juice fro ...
and salad oil:
[Joseph Moxon, ''Mechanick Exercises'', page 168, Sect. XVIII, reprint of the 1896-edition, Thoemmes Press, Bristol, UK.]
References
{{DEFAULTSORT:Type Metal
Alloys
Printing