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Eggs Nature's near perfect painting medium
No one knows when someone first used egg as a paint binder. It is easy to imagine the accidental spilling of egg into an early paint mix, or for someone to notice that spilled egg could harden into a strong film. It could have happened tens of thousands of years ago. On the other hand egg is not naturally very sticky unless in thin layers and works best on prepared surfaces. No one will ever know, it is the sort of thing that could have been invented and forgotten many times in the past. What we do know is that as the Greek practice of encaustic painting died out, egg tempera was the preferred painting medium that took its place.

By Medieval times in Europe painting on gesso prepared panels with egg tempera was normal. Oil paint existed but tempera was the preferred method. We are indebted to early writers for writing down their experience in this regard.

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The egg advantage Paint that stands the test of time
Tempera painting has many advantages, Like Acrylic to which it has many affinities, it is not prone to cracking nor does it yellow like oil paint does. Those who are unfamiliar with egg tempera often assume that the bright yellow color of the yolk must interfere with the look of the paint. Quite the opposite in fact. The yolk of an egg is an emulsion. It is a property of emulsions that they exhibit more color when wet than when dry. Take a look at an Acrylic medium, which is basically the resinous part of the paint without any color added yet. Notice it is a milky white, yet when it dries it will be crystal clear. Egg yolk is similar. It does have a small coloring component but much of the color is due to the emulsion. When the Tempera dries it loses a lot of that color immediately, and then the remainder is bleached clear by the action of light within weeks. The Tempera in fact displays little active color of its own, but instead enables the full brilliance of the pigments to show.

Some purists suggest that tempera can only be painted with tiny brushes in little strokes. This is not entirely true. It is suited to a wide range of modern and experimental techniques including spattering , glazing, scraping back and so on. It can be applied with palette knives or sponges or brushes. It is very versatile, its only real limitation is that it can never be applied thickly. There is no limit however to the number of layers, and since they dry very quickly, quite startling effects can be arrived at  in very little time. It is paint that is as new as a fresh laid egg, and as old as the old masters.

Cennini Il Libro dell'Arte -The Craftsman's Handbook
Cennino d'Andrea Cennini wrote at length on all aspects of the artist's trade in his book published in 1437. He had quite a lot to say about eggs and tempera. For different purposes he advised using the white of the egg, particularly in gilding, but for painting he recommended the yolk of the egg. He was very particular. Eggs had to be fresh and supplies needed to be kept of both country eggs and town eggs as he said the country ones were redder and better suited to the making of blue. The town eggs on the other hand were whiter and better suited to light colors. He also suggested that town eggs are suitable for painting young faces, while country eggs were better for painting old men. I can recommend reading Cennini for those who wish to immerse themselves in this otherwise lost artist's lore. Dover sells an annotated translation that should be in every artist's library.


The modern egg The problem of freshness
In medieval times it was easy to get fresh laid eggs, but unless you live in the country, keeping chickens is not feasible and we are reliant on eggs produced by large scale farming usually a long way away. The equivalent of Cennini's country eggs are the free range eggs, but it is hard to find an equivalent for his 'town eggs' as modern farmers realized in the last few years that the thing that gives egg yolks their color is protein in the diet, so now almost all chickens are fed with protein supplemented diets since yellower yolks sell better than lighter ones. It does seem however that it is the cage or barn eggs that are probably most like 'town eggs'. Getting the eggs fresh enough is important as the egg loses vitality with time and is not so suitable for painting. Avoid the cheaper generic brand eggs as they are often older than premium brands. If you live in a small town then I would advise befriending a local farmer because in the end fresh laid eggs are preferable.

I grew up in the country and learned a few tricks along the way. This is an old way of judging an egg's freshness: Hold the egg up to a light strong enough to show through the egg, if an egg is not fresh you should see the faint outline of the air space at the blunt end. New eggs have a small air space and it grows with time. Looking at eggs over a period of time will enable you to learn to judge the eggs to avoid and which are still good with high accuracy.


Separating the yolk Basic instructions
It is desirable to use yolk without any white in it. This is because the percentage of albumen in the white is too low to make a good paint. The traditional cook's way of separating whites is to crack the egg horizontally and carefully pouring the egg from one shell half to the other over a glass to catch the white. I find it easier to hold the yolk in my fingers, allowing the white to slip between the small gaps, but the easiest way is to buy a purpose made separator that neatly does the job for you. You will find them in kitchen supply stores. Which ever means you use it is important not to break the yolk membrane at this point.

Once the yolk is separated gently place it on a paper towel and roll it around taking care not to break it yet. Cennini would have dried it by passing it from one hand to the other, wiping each hand on his apron to achieve the same result. Transferring the yolk to the flat of the palm you are ready to extract the contents. using the thumb and index finger lift and hold the  yolk sack over a clean glass. Puncture the skin at the bottom with a neat hole in order to minimize the chance of skin fragments getting into the glass. A stanley knife or scalpel are ideal for this cut.

Care in obtaining the purist yolk in this way will make significantly better paints and avoid trouble down the track. The yolk is now ready to use for paint making.




References
Alberti, L B,    On Painting    1435 (Penguin Classics)
Cellini, B,    The Life Of Benvenuto Cellini,    finished 1562 but not published until 1730 (Heron)
Cennini, C d'A,    The Craftsman's Handbook.    1437 (Dover)
Doerner, M,    The Materials Of The Artist And Their Use In Painting,    1921 (Harcourt Brace)
Eastlake, Sir C L,    Materials For A History Of Oil Painting,    1847 (Dover)
Feller, R L,    Artists Pigments    1986 (National Gallery Of Art / Cambridge University)
Gottsegen, M D,    A Manual Of Painting Materials And Techniques,    1987 (Harper & Row)
Maire, F,    Colors: What They Are And What To Expect Of Them,    1910 (Drake)
Mayer, R,   The Artists Handbook Of Materials And Techniques,    fifth edition 1991  (Faber & Faber)
Merrifield, Mrs M P,    Medieval And Renaissance Treatises On The Arts Of Painting    1849 (Dover)
Muther, R,    The History Of Painting From The Fourth Century To The Early Nineteenth Century,    1907 (Putnam)
Parkhurst, D B,    The Painter In Oil   1898 (Lothrop, Lee & Shepard)
Patton, T C,    Pigment Handbook,    1973 (Wiley)
Pliny, The Elder (Gaius Plinius),    Natural History,    77AD (Penguin Classics)
Taubs, F,    A Guide To Traditional And Modern Painting Methods,    1963 (Thames & Hudson)
Theophilus,   On Divers Arts,    1125 (Dover)
Various,    Encyclopedia Britannica,    fifteenth edition 1981  (Encyclopeadia Britannica, Inc)
Various,    Paint And Painting,   1982,  (Winsor & Newton / The Tate Gallery)
Various,    The Artist's Colourmen's Story,    1984 (Winsor & Newton)
Vasari, G,   The Lives Of The Most Excellent Painters, Sculptors And Architects,    1568 (Penguin Classics)


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