What did medieval illuminators do?

Answer 1

In medieval manuscript (handwritten) books and documents the main initial letters were often decorated, often with intertwined plants and animals. These are termed "decorated" "populated" or "historiated" initials.

If the decoration also includes areas of gold leaf, the term "illuminated capitals" is applied, since the burnished gold seems to have a brilliance and light of its own, illuminating the page. Often an entire page might be used for a picture, using huge amounts of gold leaf - this is simply termed an illumination.

In the 12th and 13th centuries the gold leaf was often employed as a background, applied to a substance called gesso which raised it slightly above the surface of the page. In the 13th century it was common for the raised gold to be intricately scored with an overall pattern.

Gold leaf, once applied, was polished with an animal tooth (ox, horse or dog) because a tooth has exactly the correct hardness but is perfectly smooth and will not tear the gold. Today burnishers are usually of agate or some other hard stone.

See links below for images:

Answer 2

In the Middle Ages, books were written by hand, because there was no printing press. The books were also decorated by hand with art work, and the artists who did this were were the illuminators. They illustrated the books with pictures, but they also decorated them with such things as fancy initial letters for major sections and titles.