The leaves are applied on a plastic base treated with a separator and finished with a size coat (thermal adhesive).
The combination of pressure and temperature causes the separator and adhesive to melt, so that the gold adheres to the surface being decorated.
The film is them removed, leaving the decoration on the surface.
Used mainly for hot stamping onto leather, gold film was available in the 22 carat yellow gold colour. During the time this techinique has been replaced by other materials (mostly with plastic) and af been disappeared. For this reason today is no more available.