In this unfinished panel by Michelangelo Buonarroti you can see the entire process of tempera painting: from the naked gesso ground cartoon traces, the underdrawing, underpainting of the flesh with terre verte (green earth) color, elements of underpainting and modeling of the volumes to different levels of finish
The masterpieces of the Quattrocento Masters, splendid in color and the completeness of forms, even today impressive in their freshness and luminosity, were executed, in general, according to a very similar scheme, using egg tempera painting techniques developed and refined over the preceding centuries by first Byzantine and later European artists.
Cennino Cennini, at the very beginning of the 15th century, advised to painting two coats of green earth under the faces and naked parts of human bodies, this was also the method of the Sienese and Florentine painters of the previous century.
At the very end of the Quattrocento, Michelangelo, while working on the Madonna of Manchester underpainted the incarnati (flesh) of his figures with two layers of green earth.
Although, in general, the method of painting with egg tempera remained the same for everyone in the industry, each workshop had its own approach that concerned specific details (such as recipes for egg emulsion, pigment mixtures, etc.), rather than the process of painting itself. Some outstanding masters enriched the egg tempera method with their findings and techniques, which were then adopted by others.
Egg tempera is a flexible medium that can be handled in many ways, and one can find one’s own approach, but if our task is to understand and adopt the techniques of the Old Masters, then we must experience this complex and multi-step method of work, in which each element played its own important role: a perfectly polished gypsum ground, serving both to absorb the excess water and as a reflector of light rays; a cartoon, which allowed the artist to find precise shapes and proportions on paper and to maintain the whiteness and purity of the ground; an underdrawing, which allowed to keep the contours of shapes under control while applying numerous painting layers that where applied in a very specific way and order etc.
Handling the Color
Techniquies
When applied, tempera paint shouldn’t neither be too thick, nor run too much on the brush. We can learn about handling the color in the passage where Cennini speaks about painting with white tempera on toned paper:
HOW YOU SHOULD DRAW AND SHADE WITH WASHES ON TINTED PAPER, AND THEN PUT LIGHTS ON WITH WHITE LEAD. CHAPTER XXXI
[…] Have some clear water in a little dish, and moisten this same brush of yours in it; and rub it over this ground white lead in the little dish, especially if this is dried up. Then dress it on the back of your hand or your thumb, shaping and squeezing out this brush, and getting it empty, practically draining it. And begin rubbing the brush flat over and into the areas where the high light and relief are to come; and proceed to go over them many times with your brush, and handle it judiciously. […]
The craftsman’s handbook by Cennini, Cennino, active 15th century; translated by Thompson, Daniel Varney, 1902- ed
If we take a close look ath the brushstrokes of the Manchester Madonna, we can clearly see, that the brush strokes of the underdrawing/underpainting of Madonna’s blue garment (the one that doesn’t have color in it, was supposed to be painted with ultramarine blue in further coats of paint), their width, length and direction, resemble those of tempera brush strokes of other garments, the scroll etc. I.e. tempera painting resembled drawing on toned paper much more than it resembled pastose oil or liquid watercolor painting.
Let us also take a closer look at Giotto’s brushstrokes (early 14th century) and compare them to some of the leading Quattrocento tempera painters:
We can say that in the 15th century Italian masters got more refined and delicate, but essentially the technique of egg tempera painting didn’t change drastically.
Daniel Thompson in his book The Practice of Tempera Painting repeats Cennino’s advises on handling the egg tempera paint:
Handling the color
The secret of ease and expedition in tempera painting may be summed up in one simple formula—Get your tempering right, keep your color liquid, and have your brush squeezed almost dry. In a word, make haste slowly. Tempera painting is as far from the technique of the water color on the one hand as it is from the plastic paint-pushing of oil handling on the other. It is much closer to the technique of pencil rendering; and the tempera painter will do well to bear that comparison in mind, and handle his brush as if it were a pencil. When you want to lay a tone in tempera, do not try to float a wash, and do not try to spread the paint out with the brush; but run over the area to be covered with quick, easy strokes, like pencil marks. Follow this first coat with a second, applied in the same way, running the strokes perhaps at a little different angle, according to the form; and continue in this way until you have built up as deep and even a body of color as you want.
Thompson, Daniel V., The materials and techniques of medieval painting
The Method of Painting with Egg Tempera
Techniquies
Tempera was applied in thin layers of paint, the artist had to apply several layers of the same color one after the other in order to get an even color cast, and the depth of color and “sfumato” was achieved by applying translucent tones one over the other.
HOW TO PAINT ON PANEL
[…] it is true that the painting of the panel is carried out just as I taught you to work in fresco, except that you vary it in three respects. The first, that you always want to work on draperies and buildings before faces. The second is that you must always temper your colors with yolk of egg, and get them tempered thoroughly—always as much yolk as the color which you are tempering. The third is that the colors want to be more choice, and well worked up, like water. And for your great pleasure, always start by doing draperies with lac by the same system which I showed you for fresco; that is, leave the first value in its own color; and take the two parts of lac color, the third of white lead; and when this is tempered, step up three values from it, which vary slightly from each other: tempered well, as I have told you, and always made lighter with white lead well worked up.
The craftsman’s handbook by Cennini, Cennino, active 15th century; translated by Thompson, Daniel Varney, 1902- ed
Then set your ancona up in front of you; and mind you always keep it covered with a sheet, for the sake of the gold and the gessos, so that they may not be injured by dust, and that your jobs may quit your hands very clean.
Then take a rather blunt minever [weasel] brush, and start to apply the dark color, shaping up the folds where the dark part of the figure is to come. And in the usual way take the middle color and lay in the backs and the reliefs of the dark folds, and begin with this color to shape up the folds of the relief, and around toward the light part of the figure. And shape it up once more in this way. Then take the light color, and lay in the reliefs and the backs of the light part of the figure. And in this way go back once again to the first dark folds of the figure with the dark color. And carry on as you began, with these colors, over and over again, first one and then the other, laying them in afresh and blending them skillfully, softening delicately. And with this you have enough time so that you can get up from your work and rest yourself for a while, and reflect upon this work of yours. Work on panel wants to be done with much enjoyment.
When you have got it well laid in and these three colors blended, make another lighter one out of the lightest, always washing the brush between one color and the next; and out of this lighter one make another lighter still; and have the variations among them very slight. Then touch in with pure white lead, tempered as has been said; and touch in with it over the strongest reliefs. And make the darks, gradually, in the same way, until you finally touch in the strongest darks with pure lac. And bear this in mind: just as you prepared your colors value by value, so you put them into your little dishes value by value, so as not to take one of them for another by mistake.
And use this same system, likewise, for any color which you want to paint, whether reds, or whites, or yellows, or greens. But if you want to make a lovely violet color, take good choice lac, and good choice fine ultramarine blue; and with this mixture and white lead make up your colors, value by value, always tempering them. If you wish to do a drapery with blue with lights on it, make it lighter in this way with white lead; and execute it in the way described above.
Cennini speaks about painting draperies. The painting starts with applying three gradations of middle tone (lighter, medium and darker middle tones) of the same color hue to cover the entire area of the garment. After this step you achieve a situation similar to drawing on toned paper and you simply need to continue modeling the garment, its folds, shadows and reliefs with lighter and darker tones made with the same two pigments: a colored pigment and white lead.
It is important to understand that 14th and 15th century Italian painters are less interested in realistic optical effects (such as colored reflected light for example) as they are eager to achieve the idealized beauty of single colors and objects. For a Quattrocento painter, a precious natural ultramarine garment is beautiful in itself, and there is no need to contaminate it with other colors reflected from nearby garments or other objects.
The method of painting faces and flesh in general was different, based on juxtaposition of contrasting tones of cooler green earth and verdaccio underpainting and pinkish mixtures of flesh tones in the translucent top layers.