Some medieval readers preferred pretty pictures and shiny
decoration in their books. Not only did the sparkling page
appeal to them, it also proved their economic status, or
that the gift they gave was special. Undecorated books
were also expensive, but decorated copies cost a true
fortune, especially if gold was used. In a process called
gilding, the decorator would apply an ultra-thin film of
flattened gold to the page, which looked not unlike
our modern tin foil.
This page shows that the golden shapes were
not appended directly to the surface of the
parchment, but that they were stretched
over little "hills" of plaster (note how
the orange primer is shining through).
This way the gold would catch the
light from different angles,
maximizing its dazzling effect.