A problem with using type in a hot press

Like many printers, I’ve been using my type in lieu of brass type when making book labels with gilded letters in a Kwik-print or similar machine.
I just came across this very unwelcome passage in “An Introduction to Gold Finishing” by John Mitchell:

” ‘The composition of printer’s type.’

There are some problems associated with the use of printer’s type that should be understood before it is used for titling.

The type is cast from an alloy that contains Antimony, a metal that unlike any other, expands as it cools. Antimony is added to ensure that the alloy, as it is cast, expands into every corner of the mould.

Printer’s type is normally used cold and therefore its size will remain constant. However, when set in a type-holder and heated to around 200C, the alloy expands. When it cools, the tin and lead content contract while the Antimony expands. As the type-holder forms a barrier on five sides the only way the metal is able to expand is upwards. This leaves the type higher than the remaining unused font. Consequently, when the next job is set, the type will vary in height and the impression quality reduced.

These problems of expansion and quality will be compounded by repeated use causing the type to become virtually unusable.”

I had never heard this before. Is this common knowledge? Any input about this would be appreciated. Thanks!

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