These are my ruminations on life, design, and the pursuit of happiness…

How Type is Cast

We stopped by the International Printing Museum this weekend, for my daughter to do some Gutenberg research for a history report. While we were there, Museum Director Mark Barbour demonstrated the historical process for casting type.

First a punch is created out of steel using files, gravers, and counter punches. After the shape of the punch is satisfactory, it gets hardened and tempered over fire.

Then a matrix is made by striking the punch into a softer metal (Typically Copper).

A hand mold is used for casting, which consists of 2 parts.

When fitted together, there is a cavity

to hold the matrix.

The mold is filled from the top side with hot type metal. This is an alloy of Lead, Tin, and Antimony, which has a melting point of 550ยบ.

Type metal hardens very quickly. A good caster made about 2 letters a minute.

When the newly cast type is removed from the mold, it has a V shaped shank that needs to be removed. (You can see it here at the back of the casting)

After the shank was removed, the back end was filed smooth.

Gutenberg was not the first to create movable-type, (it was first was created in China around 1040 A.D. during the Song Dynasty by Bi Sheng.) Nor was he the first to cast metal type, (that honor belongs to Korea during the Goryeo Dynasty (around 1230).) However, Gutenberg was the first to create a workable system of moveable type, through precision manufacturing of interchangeable parts.

The type Gutenberg used to print his bible had an overall height variation of only 1/100th of an inch. This amazing feat of manufacturing was 300 years before the start of the Industrial Revolution, and 450 years before the manufacturing of Henry Ford!


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