All typesetting machines relied on type metal for their output.
The alloy of the type metal differed slightly for each machine:
| Lead | Antimony | Tin | Red copper | |
|---|---|---|---|---|
| Linotype | 85% | 12% | 3% | |
| Intertype | 85% | 12% | 3% | |
| Typograph | 75% | 22% | 3% | |
| Monotype | 72% | 19% | 9% | |
| Monotype (14 till 72 points) | 62,5% | 24,2% | 12,5% | 0,8% |
Individually, the melting point of lead is 330 degrees celsius, of antimony is 629 degrees celsius and of tin 230 degrees celsius
As an alloy, the antimony hardens the metal, the tin makes it more viscous by lowering the melting temperature of the ally, improving fluidity and it the connection between the lead and the antimony. The melting temperature of this alloy lies around 280 degrees celsius. The alloy allows to print large numbers of prints with sharp edges in the letters. When extremely large numbers of prints are necessary, more antimony and a little more tin can be added.
For Intertypes, Linotypes and Typograps, the ideal working temperature is 285 degrees celsius. It can be measured with specific thermometers. Alternatively, one could hold a thin piece of paper into the molten metal for ten seconds. When the temperature is fine, the paper will color slightly yellow. When the temperature is too high, it will color brown.
The alloy decreases in quality when re-used often. To compensate for the low quality, the heating of the machine needs to be adjusted. But also the print quality could become lower. Operators often had a furnice at their disposal to melt the type metal into bars; during this process they could add more antimony into the alloy.
It is often claimed that the type metal is lead, and that it is toxic. People like to refer to the fumes coming out of the machine, more specifically out of the melting pot.
However, it is easy to debunk this myth. In 2024, most of the former operators are living well into their eighties without any sign of lead poisoning. The fumes cannot be lead, because lead evaporates at the temperature of 380 degrees celsius. A Linotype only reaches a temperature of 280 till 300 degrees celsius. Working with a lower temperature became possible because the type metal was an alloy of lead, antimony and tin. This alloy melts at 280 degrees celsius. The fumes are often dust and ink that could attach to the alloy, and are only temporary when inserting new, dirty, type metal. When the machines runs for an hour, no fume is seen or smelled anymore. The lead itself remains within the melting pot.
Of course, some common sense remains advisable. The operators did not put the type metal in their mouth, and washing the hands after working with these kind of machines is always recommendable. But that is not only because of the lead, but also because of the ink and oil used in operating those machines.
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