Editing Type metal (section)

== 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 [[Metalworking|work]], and it is easy to [[Casting|cast]] since it melts at {{convert|327|C|F }}. However, it shrinks when it solidifies making [[Sort (typesetting)|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]], and [[ductile]] but with little [[Tension (physics)|tensile]] strength.

Lead oxide is a [[Lead poisoning|poison]], 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]] element, which melts at {{convert|630|C|F}}. Antimony has a crystalline appearance while being both brittle and fusible.<ref>Fry's Metal Foundries, ''Printing Metals'', Great Britain, revised edition 1966</ref>

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 [[Matrix (printing)|mould]] 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]] in the [[United Kingdom]] had a whole range of alloys listed in their manuals.

{| class="wikitable" style="text-align:center"
|+ Type metal compositions
|-
! Alloy type !! Tin<br>(%) !! Antimony<br>(%) !! Lead<br>(%) !! Comments
|-
| align=left | Slugcasting alloy || 3 || 11 || 86 || align=left | Ludlow/Intertype/Linotype composition for limited use and for making stereos
|-
| align=left | Eutectic alloy || 4 || 12 || 84 || align=left | Often used on slug casters and for Monotype/Elrod spacing material
|-
| align=left | Stereotype alloy || 7 || 15 || 78 || align=left | More durable intended for long print runs and curved printing plates
|-
| align=left | Monotype alloy || 10 || 16 || 74 || align=left | Most durable machine set intended to be remelted, sometimes hand set
|-
| align=left | Foundry type alloy || 18 || 28 || 54 || align=left | Traditional loose hand set type, may contain some copper
|}