by Clea Davis
Egg Tempera uses a wide variety of materials. The 15th century flourished with egg tempera artists. Most artists had assistants to help them mix and make their supplies; the artists couldn't just go to the store and buy them pre-made.
There were different workshops for making different parts of the painting.
One workshop prepared the panel on which the artist
painted. The panel is prepared by putting a pigment on the panel. The pigment
is made up of egg yolk and other ingredients. Planks of wood were joined
together to form the support, or surface, on which to paint on.
A different workshop covered the panel with a plaster made out of rabbit skin glue and gypsum. This certain kind of plaster is called Gesso. The gesso is applied in very thin coats, otherwise the panel would have too many bumps. The gesso is put on one coat at a time. The artist lets the gesso dry, then sands and polishes it. When the artist sands and polishes the panel it is called burnishing the panel. This process of polishing, sanding, and putting on the gesso is repeated many times.
Now the artist is ready to make a cartoon of what he wants to paint on the panel for the finial picture. A cartoon is a drawing of the subject the artist wants to portray. The cartoon drawing is the actual size of the final painting.
I think you could say that for egg tempera, having
a nice gold leaf background was very trendy. 
Gold leaf is
extremely thin and very hard to handle. To apply the gold leaf, you first
put a thin layer of the egg white mixture on the panel, then pick up the
piece of gold leaf and put it over the coated panel area. Next you take
your brush and gently smooth the gold. This is very tricky and takes a while
accomplish. The gold leaf is made out of gold or metal that is pounded into
very thin sheets. Some artists stamp different shapes in to the leaf.
Next, the assistants ground up different substances
to create different pigments. The pigments are made from different minerals
and clays, then mixed with egg yolks to thicken the paint and give it an
opaque and sparkly touch. Very stiff brushes are used to paint with the
pigment, which allows the artist to paint in great detail.
For more egg tempera tips; click here.