Clarified egg white or glair
Binders in medieval paint recipes
In this post, I would like tot start discussing the different binders that were used in illuminated manuscripts during the Middle Ages. This time it is about: clarified egg white or glair.
To make paint, you need a binder. That binder makes the pigment particles stick together and to the surface. In the case of illuminating manuscripts, a water based paint was used. Therefore the binders were themselves water soluble, something that is not the case with oil paint, for example, where linseed oil is the binder.
Selection and preparation
The choice of binder was important because the binder interacted directly with the optical qualities of the paint. One binder made the paint somewhat dull and another binder actually increased the gloss.
The preparation of the binder itself and the tempering (Latin: distempered = to mix well), of the paint with the binder was an important part of the whole process of book illuminating at that time. If the binder is too weak due, for example, to an incorrect ratio of ingredients between them, the paint will come off due to poor adhesion to the surface.
Medieval handbooks for painting are our main sources for the study of binders in bookillumination.
The main binders for illuminating were:
Clarified egg white, also called clarea glair, albumen, avi.
Gums such as gum arabic and cherry gum.
Glues or size of animal origin: fish glue, parchment glue.
Most binders were used only in a solution, of course there were also mixtures of different binders. Well known is the mixture of clarified egg white and gum arabic.
Optical effects
Tempering the pigments or applying the medium causes a number of optical effects. Tempering causes a paint to be opaque or transparent. This effect depends on the type and amount of binder applied. No pigment by itself is completely transparent or opaque. The transparency of a pigment is partly determined by the medium that surrounds the pigment granules.
The amount of medium is also important. Sometimes there is just enough of the binder to bind the grains. If more is added and then a so-called optical bridge is created, the light can penetrate differently and produce a different reflection of light.
Clarified egg white
Clarified egg white was long the standard medium of the book illuminator. The word comes from Latin: (clarea, clarus = clean). Clarified egg white is the liquid that has settled, from beaten egg white. Egg yolk was mainly used for panel painting and occasionally used “strategically” as with vermillion. Adding egg yolk gave this colour extra lustre. In particular recent research has revealed that more egg yolk was used after all.
Egg white / protein is the clear liquid inside an egg. It forms around fertilized and unfertilized egg yolks. The main natural purpose of protein is to protect the yolk and provide extra nutrition for the growth of the embryo (when fertilized). Protein consists mainly of water 90% containing 10% protein. Egg white, taken directly from an egg, does not mix easily with water, it is stringy and can hardly be painted. The structure of egg white must be changed in order to be able tot paint with it, to use it as a binding agent.
In the Middle Ages, people used twigs or a sponge to make egg whites into foam. This was a labour-intensive process, paid very close attention because if it was not worked properly, you did not have a good binder. The advantage of whipping with twigs was that it produced a cleaner result. A sponge that constantly sucked and squeezed out the egg whites by hand was prone to the dirt from the hands. Furthermore, a way of pressing the egg white through a woolen or linen cloth is also described.
There is an 11th-century anonymous work describing the process of making glair. It is called: “De Clarea”.
Recipe for making clarified egg white
Take an egg and separate the yolk from the white. You can do this by hand or with an egg separator. Put the egg in a bowl and you can stil fry and eat the yolk.
Beat the egg white to a thick froth. Leave it all in the fridge overnight.
The next day, pour the drained liquid from the bottom into a glass jar. Now you have clarified egg white. You can use it pure or diluted. I personally prefer pure because it the forms a stronger binder for pigments.
You can now store the clarified egg white in the fridge. However, it is useful to add some preservative. I personally use clove oil, add one of two drops and then close the jar tightly. That way, I was able to keep it for up to six months and it was still usable. The egg white does get a bit darker in colour. For this, see the photo below. On the left you can see the fresh egg white and on the right the old egg white. The amount in the left-hand jar comes from two eggs.
As already mentioned, clarified egg white or glair was widely used by illuminators. However, only clarified egg white gives a somewhat matt character to the paint. Not all pigment particles are surrounded by the egg white. As a solution, paintings were therefore sometimes “varnished” with strong glair and some honey. This mixture gave the colors more depth and richness. We also see that some gum was often added to make the colors richer and deeper. In de 14th century the preference for gum Arabic increased, especially for the blue colours. They become richer in colour when using gum Arabic.
We store the egg white in a glass jar, the illuminator put it in a used eggshell with the cap, from the other side of the broeken egg on it. Against rotting they used ‘Realgar’ = arsenic sulphide and also vinegar.
Obtaining and storing glair in the workshop of an illuminator was not easy. In winter, chickens laid almost no eggs in those days. There was no artificial light in the hen house because a hen needs a long day of light to lay eggs. In summer, the glair dried out quickly and in winter it could even freeze. Theophilus Presbyter (1122) wrote in his work: “To prepare the egg white in summer with some water and in winter without”. This to avoid drying out.
Other works recommended to wait a few days for using the clarified egg white and not immediately after preparing it.
A disadvantage of egg white as a binder is the formation of air bubbles in the paint mixture when tempering and painting. (See photo above). This is annoying because they burst open and at every spot where a bubble was present, a light spot can be seen after the paint layer dries. You then get an irregular paint with pits, and dots. A Medieval solution to it was adding: earwax.