Here I am using an eyedropper to add water to egg yolk, in preparation for mixing with dry pigment (which has had a few drops of water added to IT to make it easier and safer for mixing with the yolk).

egg tempera (general)

(15 min into it, there is a great demo of Wyeth's process!)

 

(see his brush and a bit of process!)

 

egg tempera (icons)

(history, explanation, process by Father Canuli at Villanova University)

 

(just process, including gold leaf application. The location and iconographer is not noted)

LINKS for Egg Tempera Videos

On Sept 13, 2017, I gave a presentation on the process of painting with egg tempera, at the Virginia Museum Council Book Club meeting. The book under discussion was A Piece of the World, by Christina Kline Baker, about Andrew Wyeth, Christiana Olson, and the now-famous painting, Christina's World. Below are some videos of the egg tempera process I think you might find interesting. 

 

Wyeth worked in water color as well as egg tempera. Christina's World was painted in egg tempera on panel. 

 

I will be adding more as I have time to do so. Right now, I find these the most illuminating. The processes described below demonstrate the 'linear' approach of application and to the 'puddle; approach.

 

Wyeth laid down his paint in tiny linear strokes, some parallel, some cross-hatched, some splattered. 

 

The iconography technique seen below uses a more 'puddle' approach, marks put down with a slightly larger brush. In either technique, the paint will lift when painted over it if the newer paint is too wet, or the pressure is too hard.