MITRA Forum Question Details

​Hello,

This question was directed to the egg tempera moderator who initially failed to answer because  questioner and moderator are one and the same (me).  So, I did more research and wrote to several museums for information, which proved helpful. The updates to my thoughts on ET and illuminated manuscripts are posted below (for anyone still puzzling over an answer).  Additional comments are, of course, welcome.  

Koo Schadler

EGG TEMPERA ON PARCHMENT/VELLUM[1]

Medieval manuscripts are often said to be painted in tempera.  It's uncertain how many are actually egg yolk tempera, or are a generic “tempera paint" (a term used by museum to denote many types of water-based mediums).  When the binder in a manuscript is precisely identified, it's most often “opaque watercolor", i.e. gouache (gum Arabic), glair (egg white), or distemper (animal glue).[2]  There is also a degree of mixed mediums in manuscripts; some illuminators used different binders, depending on individual expertise (i.e. artists who were also panel painters, already familiar with egg tempera, more often incorporated it into a text) or perhaps on visual goals (i.e. amount of saturation or shine in a color).[3]

Regardless of the history (seemingly limited) of egg tempera on parchment and vellum, contemporary practitioners should note certain inherent constraints.  Animal skins are extremely hygroscopic (water-loving); they really want to move with changes in humidity, and do so quickly.  This is true even when attached to a rigid support; the expansion and contraction rates of wood and animal skin are very different and, depending on how the individual strengths of each material compete with one another, stresses can occur that deform or crack the paint, skin, or even wood panel (i.e. a thick vellum attached with strong adhesive can potentially deform a low density fiberboard).  Instead, to impart some rigidity to animal skin, it's best to bind it within a manuscript, as was traditionally done.  Binding accounts, in part, for the excellent condition of many medieval texts; the format kept images secure and less susceptible to light, dust and humidity.  

​Given the inevitable challenges of a brittle medium atop a moving support, when painting atop animal skin it's important to paint thinly (more like watercolor), in just one or a few layers.  Small particle size pigments hold up better than large particle sizes (which are less flexible).  Proper framing, and keeping an image in a stable environment (consistent relative humidity of about 50%) are also helpful.  Applying a ground is not necessary when painting on parchment; animal skins are naturally porous and essentially the same glue used in traditional gesso.  

[1] Parchment is a general term for animal skin - usually calf, goat, or sheep - prepared for writing or illustration. Vellum (French for veau, or veal) refers specifically to calfskin parchment and generally has fewer natural imperfections than parchment.  

[2] Glair, made from egg white, is even more brittle than egg tempera.  However it was applied very thinly; and, as noted, the manuscript format countered some of the inherent challenge of a brittle medium. 

[3] The Fitzwilliam Museum, Cambridge, England (www.fitzmuseum.cam.ac.uk/illuminated/manuscript) has an excellent website devoted to illuminated manuscripts, with descriptions of materials and methods used in each manuscript.  When I asked them about the presence of yolk binder in manuscripts, they replied, “Research is continuing, and the presence of lipid binders (i.e. containing actual egg yolk, which characterizes 'real' egg tempera, as opposed to simply egg white) is being noted in more manuscripts. [Egg tempera] is not 'standard practice', but a choice made by illuminators with excellent mastery of their materials and their intended effects. Most medieval and Renaissance manuscripts were probably painted mainly with gum Arabic or egg glair." The museum recommended the following site, with many short but 'illuminating' videos: www.bl.uk/medieval-english-french-manuscripts/videos/

I also was sent this reference by a fellow painter: “...[the manuscript]… had their central figures painted in egg yolk tempera…This was an unexpected find because the most widely used paint binding media for miniature paintings on parchment were reported not to be egg yolk tempera but rather protein-based media (animal skin glue and egg white) or polysaccharide-based media (such as gums)."   F. Gabrieli1, K. A. Dooley, M. Facini, J. K. Delaney. Near-UV to mid-IR reflectance imaging spectroscopy of paintings on the macroscale - Scientific Figure on ResearchGate. Science Advances, p 1-10.

​​

​Hello,

This question was directed to the egg tempera moderator who initially failed to answer because  questioner and moderator are one and the same (me).  So, I did more research and wrote to several museums for information, which proved helpful. The updates to my thoughts on ET and illuminated manuscripts are posted below (for anyone still puzzling over an answer).  Additional comments are, of course, welcome.  

Koo Schadler

EGG TEMPERA ON PARCHMENT/VELLUM[1]

Medieval manuscripts are often said to be painted in tempera.  It's uncertain how many are actually egg yolk tempera, or are a generic “tempera paint" (a term used by museum to denote many types of water-based mediums).  When the binder in a manuscript is precisely identified, it's most often “opaque watercolor", i.e. gouache (gum Arabic), glair (egg white), or distemper (animal glue).[2]  There is also a degree of mixed mediums in manuscripts; some illuminators used different binders, depending on individual expertise (i.e. artists who were also panel painters, already familiar with egg tempera, more often incorporated it into a text) or perhaps on visual goals (i.e. amount of saturation or shine in a color).[3]

Regardless of the history (seemingly limited) of egg tempera on parchment and vellum, contemporary practitioners should note certain inherent constraints.  Animal skins are extremely hygroscopic (water-loving); they really want to move with changes in humidity, and do so quickly.  This is true even when attached to a rigid support; the expansion and contraction rates of wood and animal skin are very different and, depending on how the individual strengths of each material compete with one another, stresses can occur that deform or crack the paint, skin, or even wood panel (i.e. a thick vellum attached with strong adhesive can potentially deform a low density fiberboard).  Instead, to impart some rigidity to animal skin, it's best to bind it within a manuscript, as was traditionally done.  Binding accounts, in part, for the excellent condition of many medieval texts; the format kept images secure and less susceptible to light, dust and humidity.  

​Given the inevitable challenges of a brittle medium atop a moving support, when painting atop animal skin it's important to paint thinly (more like watercolor), in just one or a few layers.  Small particle size pigments hold up better than large particle sizes (which are less flexible).  Proper framing, and keeping an image in a stable environment (consistent relative humidity of about 50%) are also helpful.  Applying a ground is not necessary when painting on parchment; animal skins are naturally porous and essentially the same glue used in traditional gesso.  

[1] Parchment is a general term for animal skin - usually calf, goat, or sheep - prepared for writing or illustration. Vellum (French for veau, or veal) refers specifically to calfskin parchment and generally has fewer natural imperfections than parchment.  

[2] Glair, made from egg white, is even more brittle than egg tempera.  However it was applied very thinly; and, as noted, the manuscript format countered some of the inherent challenge of a brittle medium. 

[3] The Fitzwilliam Museum, Cambridge, England (www.fitzmuseum.cam.ac.uk/illuminated/manuscript) has an excellent website devoted to illuminated manuscripts, with descriptions of materials and methods used in each manuscript.  When I asked them about the presence of yolk binder in manuscripts, they replied, “Research is continuing, and the presence of lipid binders (i.e. containing actual egg yolk, which characterizes 'real' egg tempera, as opposed to simply egg white) is being noted in more manuscripts. [Egg tempera] is not 'standard practice', but a choice made by illuminators with excellent mastery of their materials and their intended effects. Most medieval and Renaissance manuscripts were probably painted mainly with gum Arabic or egg glair." The museum recommended the following site, with many short but 'illuminating' videos: www.bl.uk/medieval-english-french-manuscripts/videos/

I also was sent this reference by a fellow painter: “...[the manuscript]… had their central figures painted in egg yolk tempera…This was an unexpected find because the most widely used paint binding media for miniature paintings on parchment were reported not to be egg yolk tempera but rather protein-based media (animal skin glue and egg white) or polysaccharide-based media (such as gums)."   F. Gabrieli1, K. A. Dooley, M. Facini, J. K. Delaney. Near-UV to mid-IR reflectance imaging spectroscopy of paintings on the macroscale - Scientific Figure on ResearchGate. Science Advances, p 1-10.