 
in our age of mass production, most painters buy their materials 
ready-made. 
but during the middle ages and the renaissance, painters prepared many of 
their pigments in their own workshops. 
they made them out of colored materials and pieces of earth, which they 
ground into fine powder and mixed with water to form a paste. 
they knew how bright or dull certain colors would appear after drying, and 
they knew fairly well what their paintings would look like after ten, twenty, 
or even a hundred years. 
because artists in those days knew their materials so well, many of their 
paintings are still in excellent condition. 
look, for instance, at the clear, beautiful colors in the 
fifteenth-century manuscript illumination reproduced here (plate 1). 
the ultramarine blue used for both the sea and the sky was made from a 
semi-precious stone called lapis lazuli. 
before applying each mixture of pigment and water, the artist added a 
gummy substance to make the paint adhere firmly. 
manuscript illuminators often used the white of an egg, but painters who 
worked on canvas or wooden panels used the yolk. 
egg tempera, as this kind of paint is called, dries so fast that each new 
stroke of color can be added almost instantly without blurring or mixing. 
in a period such as the early renaissance, when precision of detail was so 
highly admired, egg tempera was the perfect medium. 
panel paintings were often much larger than manuscript illuminations but 
could be just as precise in detail (plates 2 and 3). 
the surface of the panel was prepared with many layers of a fine white 
plaster called gesso, rubbed down to a smooth finish. 
