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Persian and Indian pigments

At the start of this year we had a special guest in the studio in the form of Julia Poirier, a conservator from the Derry and Raphoe Diocesan Library Project, who came to work with us at the Chester Beatty Library for a fortnight. Whilst here, she conserved a collection of disbound Indian illuminations and has written up the project here: http://derryandraphoe.wordpress.com/

As this followed hot on the heels of my conservation treatment of three Persian illuminated folios, there was lots of talk about the pigments typically used in Indian and Persian art: commonly seen pigments include ultramarine (lapis lazuli), malachite, azurite, verdigris (a general term for copper-based greens), red lead, vermillion, cinnabar, safflower, madder, carmine lakes (kermes and cochineal), orpiment, Indian yellow, lead white, carbon black, and precious silver and gold. However, this list is by no means exhaustive and many more pigments were also used.

In the Conservation lab we have several samples of powdered pigments available for experiments, mainly purchased from the magnificent Cornelissen’s who still supply traditional artists’ pigments. We decided it would be worth mixing up some of these pigments in order to paint out some colour charts which we could then conduct various tests upon.  The pigments we had available included mineral-based (lapis lazuli, azurite, malachite); synthesised pigments based on copper, lead and mercury (verdigris, lead white, red lead, vermillion); an organic red from plant root (rose madder); carbon black, and silver. For more about pigments, Boston’s Museum of Fine Arts has an excellent database.

Verdigris

Aside from the silver, mixing up the pigments followed the same procedure: the powder and a small amount of gum arabic (a binder harvested from the acacia tree) were worked together using a glass muller on a tile, until the particle size of the pigment was reduced and a smooth paint texture was formed. A small amount of water could also be added in order to loosen the viscosity.  We also attempted making a purple pigment by combining lapis lazuli and rose madder, as the conservation of Per 163. 82  had raised questions about which combinations of pigments may have been used to make purples.

Turning silver into a paint proved to be a much more laborious task, as silver leaf and gum arabic were mixed using just fingertips in a shallow bowl (traditionally a shell was probably used as the mixing and storage vessel). Even taking it in turns and working on it for a few hours at a time, it still took several days to break the silver leaf down into particles fine enough to be used as a paint.

Silver leaf

Turning silver leaf into a paint

Once mixed, each pigment was painted out onto Indian Islamic-style paper (surface sized and burnished).  We painted out several squares of each pigment so that we could have a control for each colour, and then separate areas on which we could experiment with applying consolidants.

Verdigris, malachite, azurite, lapis lazuli, rose madder + lapis lazuli, rose madder, vermillion, red lead, lead white, carbon black and silver

Mixing and painting out the pigments was revealing in itself, as we were able to learn first-hand more about the handling properties of each. Some, like the malachite, proved difficult to work with as the particles are large and heavy, making the paint difficult to manipulate. The coverage provided by malachite was also fairly poor, showing why layering of the pigments was a necessary step for miniature artists. Others, such as red lead, provided opaque, even coverage immediately and were fluid and easy to handle.  Two tones of purple were achieved by combining rose madder and lapis lazuli (see below), but it would of course be possible to create further variations using these two pigments.

Lapis lazuli, rose madder, and combinations of the two (middle row)

Following preparation of the pigments and painting out the samples, we were then able to experiment with applying consolidants to some of the samples to see how they reacted. This is an ongoing project which I hope to detail at a later date. In the meantime, I have observed that the silver already shows signs of tarnishing, revealing just how quickly the processes of degradation can take place.  Additionally, we have observed that the carbon black has cracked in places, perhaps suggesting that we had included too much binder in the mixture.

Silver showing signs of tarnishing

For me, perhaps the most useful element of this experiment is that I feel much more able to identify some of these pigments in manuscripts, having had the experience of preparing them myself. The particular, unique tones of malachite, for example, seem suddenly much more obvious to my eye, which can be very useful when deciding upon conservation treatments. I also have renewed respect for the craftsmen that prepared these pigments, as the time and effort taken to grind them down was much greater than I had conceived of.

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