Sunday, October 24, 2010

Egg Yolk

It was nearly 2,000 years ago when egg yolk was first mixed with pigments. That seems like a long time ago but there are records of chickens being domesticated for 8,000 years!

There's some chemistry of the drying reactions that still escapes me but I can see the results. My egg and pigment mixtures dry on the palette rather quickly. I've learned to tip the palette to puddle my mix. I'm looking at small and rounded palette wells. This evening I mixed pigment and water but only used a bit with egg. When that was gone, I mixed more.

You see, unlike watercolor, once tempera begins to set up and dry, there is no bringing it back. It's gummy on its way to hard, no longer water soluble.

From The Chemistry of Paints and Painting by Arthur Herbert Church:

"But the yolk of an egg contains other substances besides albumen. First of all, the albumen present is accompanied by another similar compound called vitellin, which closely resembles it in composition and properties, and which, for our present purpose, we need not further describe. Of albumen and vitellin, taken together, egg-yolk contains, as we have seen, not less than 14 or 15 per cent. But egg-yolk is something more than a solution of these two similar bodies. It is, in fact, an oily emulsion, in which innumerable minute globules of a thick, fatty oil are suspended in an albuminous solution. And, moreover, the amount of this oil is large; for there is 30 per cent, of it as against 15 per cent of albumen and vitellin taken together. Hence it happens that egg-yolk, the usual vehicle for pigments in the best kind of tempera-painting, must be regarded as essentially an oil-medium. As it dries, the oil hardens, and remains intimately commingled with the albuminous substances left behind on the evaporation of the water present. These albuminous substances coagulate and become insoluble in the lapse of time—a change greatly accelerated by the old practice of exposing the finished tempera picture to sunshine previous to varnishing it."


  1. Just brilliant. Barely second-best to actually painting is the geekery thereof. And that paragraph is a beautiful example!

    Out with my premixed tempera later on to see whether it will go onto untreated goatskin better than gouache. I suspect yes. If so, I will be doing some eggyolkification myself and some test pieces prior to attacking a whole goatskin with miniatures. Reports to follow.

    Meanwhile your progress is as always inspiring -- and the lake is beautiful in this season!

  2. Wow! Go for it, Katharine! Waiting patiently (not) for your report. ;-)

  3. Just a thought but you might try a bit of egg yolk with half as much water in very thin layers, even without pigment. The chemistry of the tubed material is different enough that the results might be noticeable.

  4. Hm! And put the tube paint on top? That might be interesting too: a 'tempera-tempered' surface.

    Experiments on paper so far indicate that the pre-mixed tempera is rather gouachey in texture, and still lifts off a little after application. I shall see what condition it's in tomorrow morning.

  5. Premixed tempera in tubes has added oil that changes the properties somewhat. (It seems not very popular in the tempera forums.) Texture might be thicker and I have read that mixing with water could bring it down closer to the feel of egg tempera. It seems that one could consider this tubed material (Sennelier, Rowney, Old Holland) to be a different medium.

    I wish I now knew more regarding drying properties. I am in process of researching enough to post on this with some detail. If you are trying to test "real" egg tempera on goat skin, I would encourage you to grab an egg and have at it, either with pure pigment, an aqueous dispersion, or tubed watercolor.

    Hope I am not sounding too much like a snobby egghead! :-)

  6. John, you don't sound in the least like a snobby egghead!

    Without wanting to clutter up your blog with extraneous detail, here's my initial report on premixed tempera.

    The premixed tempera (zinc white) does still, after a night's rest, lift off much more easily than I believe 'real' tempera would. My limited experience of the real thing suggests that once it's dried, it's dried quite solid and water-resistant, much as egg yolk does on breakfast plates :-)

    The premix also does indeed come onto and off the paintbrush much more easily and smoothly when mixed with about a quarter as much water again -- but then it doesn't cling to the goatskin's smoother, glossier patches unless they're pounced or sanded first -- which makes the diluted tempera just as finicky as plain watercolour without the advantage of transparency.

    It's quite nice to paint on top of, but not significantly different from any good painting surface in terms of evenness or fineness of line.

    The premix mixes well with watercolours of various textures and there is a lovely soft quality to the colour and texture. The colours when dry are quite a lot more intense than when wet, like gouache but perhaps even more so. This is more about the high white content than anything to do with its nature as tempera, though, I think.

    So now it just needs a few hours completely free to sit down and do it properly with an egg yolk. Thank you for the encouragement, I'll be thinking of you as I dabble ;-)

  7. Yes, exactly like egg on a plate! Real tempera will dry to touch in literally seconds. Now as for stickability...

    Mention is often made of the gessoed surface as sufficiently absorbent. That is, to get that first layer to bind well. I wonder how receptive the goat skin will be?

    Please do keep us all informed here. These are incredibly rich and entertaining exchanges.