Today is the feast of St. Luke the Evangelist, the patron saint of artists and iconographers). I love this particular icon of him painting the icon of Mary, the Mother of God and Jesus, who are posing for him. The the composition of this icon is based on a drawing by my master teacher, Pere Igor. Unfortunately, I never had a chance to ask him why the pose of the two figures in the icon are so different from the actual figures who are standing in front of him. So on his feast I was able to make a bit more progress on highlighting the figure of the Mary and Jesus in the center of the triptych. Her garment is highlighted in paint; the figure of the Christ Child is highlighted with gold leaf (sometimes called 'gold assist').
His little overgarment is highlighted in much the same way as with paint, only using finer, sharper brush strokes. Instead of paint, gold size (a crushable compound called a mordant that dries tacky) is applied to all of the areas where a gold line is desired. It has to be thick enough so the brushstrokes will hold their shape and fluid enough to paint with.
When the size has set (depending on the size it will remain open for at least an hour or two), gold leaf is then pressed onto the areas painted with size. And voila! The gold lines appear as if by magic on the icon (usually) when the excess gold is gently brushed away with a soft brush.
Then follows the painstaking faulting of the gilded areas, because inevitably, their will be lines here and there that the gold did not adhere to or a line or two the one wielding the brush failed to paint in, and so the process is repeated once or twice (or again and again if you are having a particularly bad day) until all the gold lines are complete.
A couple of coats of shellac to fix the gold leaf (which is surprisingly fragile), followed by redrawing the lines as necessary to pull it all together.