Product Code Database
In printing, type metal refers to the metal used in traditional Movable type and hot metal typesetting. Historically, type metal was 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%. 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 point, 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.
After much experimentation it was found that adding 's tin, obtained from cassiterite, 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.
Alchemy had shown that when stibnite, an antimony sulfide ore, 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, given that it has the curious property of diminishing the shrinkage of the alloy upon solidification.
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 is exceptionally soft, malleable, and ductile but with little tensile strength.
Lead oxide is a Lead poisoning, 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.
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 to produce clear, easily read printed text on the page.
| + Type metal compositions |
| Ludlow/Intertype/Linotype composition for limited use and for making stereos |
| Often used on slug casters and for Monotype/Elrod spacing material |
| More durable intended for long print runs and curved printing plates |
| Most durable machine set intended to be remelted, sometimes hand set |
| Traditional loose hand set type, may contain some copper |
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 (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 in a laboratory.
Apart from this the two Monotype companies in the United States 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.
| + Type metal alloys mentioned in the UK-Monotype-caster manualsN.N., The Monotype Casting Machine, The National Committee for Monotype Users' Associations, London, UK, 1952. | |||||
| 1 | 6/15 | 261 | 240 | 23.0 | Routine |
| 2 | 10/16 | 273 | 240 | 27.0 | Dual (machine & hand composition) |
| 3 | 9/19 | 286 | 240 | 28.5 | Routine machine composition |
| 4 | 13/17 | 283 | 240 | 29.5 | Catalogues |
| 5 | 12/24 | 330 | 240 | 33 | Display type, heavy duty jobs |
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.
| Typograph | 3/12 | 250 | 280...290 | 310...330 | 19 |
| Ludlow | 5/12 | 245 | 270...285 | 300...320 | 21 |
| Lino/Intertype a | 5/12 | 245 | 270...285 | 300...320 | 21 |
| Lino/Intertype b | 6/12 | 243 | 270...285 | 300...320 | 21.5 |
| Lino/Intertype c | 7/12 | 241 | 270...285 | 300...320 | 22 |
| Stereotyping | 5/15 | 265 | 320 | 320...340 | 23 |
| Stereotyping | 7/14 | 258 | 315 | 320...340 | 23 |
| Monotype a | 5/15 | 265 | 350 | 330...350 | 23 |
| Monotype b | 8/15 | 260 | 360 | 350...370 | 25 |
| Monotype c | 7/17 | 280 | 370 | 360...380 | 26 |
| Monotype d | 9/19 | 285 | 390 | 380...400 | 28.5 |
| Monotype e | 9.5/15 | 270 | 360 | 350...370 | 26 |
| Monotype f | 9.5/17 | 280 | 380 | 370...390 | 27.5 |
| Monotype g | 10/16 | 275 | 370 | 360...380 | 27 |
| Regeneration a | 9/11 | — | — | — | — |
| Regeneration b | 9/12 | — | — | — | — |
| Regeneration c | 9/16 | — | — | — | — |
| Support metal a | 1/2 | 310 | — | 360...380 | 6 |
| Support metal b | 3/5 | 295 | — | 340...360 | 14 |
| Support metal c | 5/5 | 280 | — | 340...360 | 16 |
| Typefounding | 5.5/28.5 | 360 | — | 420...430 | 29.5 |
Every time type metal is remelted, tin and antimony Oxidation. 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 and remain economically feasible.
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 system. This alloy has a clear melting point, at 252 °C.
Increasing the antimony content beyond 12% will lead to predominantly antimony crystallization.
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.
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.
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. These oxides are removed with the dross 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.
Brass and zinc should therefore be removed before remelting. The same applies to aluminium, although this metal will float on top of the melt, and will be easily discovered and removed, before it is dissolved into the lead.
The "antimony" here was in fact stibnite, antimony-sulfide (Sb2S3). The iron was burned away in this process, reducing the antimony and at the same time removing the unwanted sulfur. 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. The Typecasters, Ellic Howe in: The Monotype-recorder, vol. XLI, summer 1957, nr.1
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, a labor force that includes .Joseph Moxon, Mechanick Exercises, page 167, Sect. XVIII, reprint of the 1896-edition, Thoemmes Press, Bristol, UK.
As a supposed antidote to the inhaled toxic metal fumes, the workers were given a mixture of red wine and salad oil:Joseph Moxon, Mechanick Exercises, page 168, Sect. XVIII, reprint of the 1896-edition, Thoemmes Press, Bristol, UK.
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