This is a letter I wrote in response to a question posed on the scribes mailing list at [email protected]. The quotes are useful in determining the usage of egg yolk as a binder in books, and so I present it here without modification.
Greetings from the humble scribe, Merouda Pendray.
M. Ranthulfr asked:
So here's some questions for you folks who use yolk on scrolls:
1) How do you keep it from flaking and cracking? Do you add something,
paint it thinner, or just not seem to see a problem after the first year or
two?
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Of course, I am making the assumption that you are making your tempera paints by wetting a pigment with water enough to make a paste, and adding a solution of 50% egg yolk & 50% water to the pigment paste. The yolk does work well when combined with a gum binder, and you will have good success with this; I have used 50% egg solution with 50% gum solution to my satisfaction; you may prefer something else. I haven't tried any of the other flexability agents (sweeteners), as I have been sufficiently satisfied with gum.
When painting with tempera straight, I also find that painting it thinnly helps, as does painting in layers that dry completely between, and mounting the page to foam core. I suspect that a THIN layer of gesso first washed into the painting area may help, but have not yet tried this. I also suspect that a varnish may help, but I am insufficiently interested in this to try it. Instead, I have washed weak gum arabic over such areas, and have had no problems.
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2) What period sources do you have for its use on the page as opposed to on
the panel?
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Ranthulfr, I have no evidence to suggest that egg yolk alone as a binder was ever used to bind all the pigments in all their uses throughout an entire manuscript. The egg yolk binder is too soft to stand up to the wear and tear of book usage, so I doubt I will EVER find this, but I won't say either that there was NEVER a manuscript made completely with straight-yolk as a binder (after all, they had to figure out that this was not the best of ideas somehow, and it could have been by the making of books that didn't stand the test of time).
There is evidence, however, that egg yolk was used in books, either in combination with other binders to bind a particular pigment (red being the most notable example) or as a supplimentary paint.
Here are some quotes for you. :)
From _De Arte Illuminandi_:
page 2, in section 3: "The solutions with which colors are tempered for use on parchment"
"The solutions with which colors are laid are as follows: the glair of hens' eggs, and their yolks, gum arabic and gum tragacanth dissolved in pure spring water"
Page 15, in section 20, (The Colors: How they should be ground and mixed together and laid on parchment), specifically referring to
"some people work {verdigris} up with the juice of rue and a little saffron, and temper it with the yolk of egg".
From Cennini's _Craftsman's Handbook_, Thompson's translation.
Chapers XXXI and XXXII refer to drawing on tinted paper; I'm not typing in the whole shebang, but the relevant section is: "Take white lead ground with water, and temper it with yolk of egg; and it blends like an ink wash , but it is harder for you to handle, and more experience is needed." (page 19)
Chapter LVI, from the section dealing with which temperas to use with which pigments:
"And {verdigris} is especially good on paper or parchment, tempered with yolk of egg." (page 33)
Again that reference to verdigris with egg yolk!
In _Booke of Secrets_;
(Another yellow) Take saffron and mix it with the yolk of an eg, and it maketh a faire shining color. (page 27).
In the period references I checked (Cennini, _De Arte Illuminandi_, Theophilous, _Strasburg Manuscript_, Hilliard's _Arte of Limming_, _Staff of the Scribe_ {in _Medieval Arabic Bookmaking_}, _Booke of Secrets_ {In _Manuscript Inks_}, _Gottingen Model Book_) , if egg yolk was mentioned in relation to book making, it was far more typical to describe a binder of egg yolk mixed with another binder, but, as you will note above, there were some exceptions. A couple of the above give some pretty specific recipes for the mixed binders, generally in relation to the various red-orange pigments.
And then, there is my theory. I have sometimes run across notations in modern exhibition catalogues that describe the type of paint. In those books that use more specific descriptions (i.e., everything is not the same sort of paint), I have noted that some of the paints are described as "tempera". I know that they could be using this as a generic term that describes any medieval paint that isn't specifically identifiable, but I have also noted that those that are identified as "tempera" are painted with the cross-hatching method of shading--the method by which egg-yolk paintings are shaded. Now, I understand that this could be for a variety of reasons, but I suspect that in at least some of the instances, it is because egg-yolk based paints really are being used.
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I'm still accumulating knowlege. I plan to do something with it one
of these days. This is one of my gaps. Thanks ahead of time to whoever
replies!
Ranthulfr
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Laird Almighty, will we EVER know everything we want to? I keep trying; maybe some day we'll get there. :)
I hope this will be helpful to you. Yours, Merouda
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