Editing Type metal (section)

== Alloys for mechanical composition ==
Most [[mechanical typesetting]] is divided basically into two different competing technologies: line casting ([[Linotype machine|Linotype]] and [[Intertype Corporation|Intertype]]) and single character casting ([[Monotype Corporation|Monotype]]).

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 (typesetting)|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.

{| class="wikitable" style="text-align:center"
|+ Type metal alloys mentioned in the UK-Monotype-caster manuals<ref>N.N., ''The Monotype Casting Machine'', The National Committee for Monotype Users' Associations, London, UK, 1952.</ref>
|-
! width=15 | 
! width=35 | Sn/Sb<br>(%)
! width=40 | Liquid&nbsp;at<br>(°C)
! width=40 | Solid&nbsp;at<br>(°C)
! width=40 | Hardness<br>([[Brinell hardness test|Brinell]])
! Purpose
|-
| 1
| 6/15
| 261
| 240
| 23.0
| Routine
|-
| 2
| 10/16
| 273
| 240
| 27.0
| Dual<br>(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.

{| class="wikitable"
! Usage
! Sn/Sb<br>(%)
! Liquid at<br>(°C)
! Casting at<br>(°C)
! Remelting at<br>(°C)
! Hardness
|-
| '''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
|-
|}

=== Dross ===
Regeneration-metal{{clarify|date=June 2023}} was melted into the [[crucible]] to replace lost tin and antimony through the [[dross]].{{cn|date=June 2023}}

Every time type metal is remelted, tin and antimony [[Oxidation|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]] 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&nbsp;°C, this mixture will be completely molten and a homogeneous fluid even at temperatures as low as 371&nbsp;°C. Letting this mixture cool the alloy will remain liquid even through 355&nbsp;°C, the melting point of pure lead. Once the temperature reaches 291&nbsp;°C, lead [[crystal]]s will start to form, increasing the cohesion of the liquid alloy. At 252&nbsp;°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&nbsp;°C.

Using a 12% antimony, 88% lead mixture prevents crystal formation entirely, becoming a ''[[eutectic system|eutectic]]''. This alloy has a clear melting point, at 252&nbsp;°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&nbsp;°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 machine|Linotype]] and [[Monotype System|Monotype]] 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]]. 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.