25 January 2016

Studio Workshop - Paints and Pigments

Artist Jessica Houston and natural pigment samples.

On December 19, I took a studio workshop at the Metropolitan Museum in New York, led by artist and educator Jessica Houston. Ms. Houston led the twenty or so participants through a whirlwind of activities; there was little time for coherent note-taking or reflection. So, this blog post is not a comprehensive report but more a series of images from the workshop - a "taste" of the day's agenda.

Before the  invention, in 1706, of the first commercially available pigment, Prussian Blue, artists had to make their own pigments, from mineral, animal or vegetable sources. Ms. Houston gave us a slide tour through some of the ancient and medieval pigments. The ancient Egyptians used six colors in their art: black, white, yellow, red, blue and green. Each color had religious symbolism and hence was deployed in a very specific way. Black, derived from carbon sources such as lamp black - soot - was the symbol for death and the underworld while white, made from chalk, stood for purity, and so on.

Slide show of ancient and medieval art and pigments.

We visited some of the medieval and ancient Egyptian galleries of the museum, and Ms. Houston indicated which pigments were used in the artwork. For me, this was the highlight of the day, and demonstrated the unique advantage of an art class held at a museum with encyclopedic holdings of art.

The beautiful ancient Egyptian sculpture below is wood coated with plaster, and the pigments used for the woman's dress include malachite green, cinnabar red, and some kind of carbon-based material for the black areas.

Estate figure, ca. 1981 - 1975 B.C.

While the slide show and gallery tour were fascinating, we were there to learn by doing, so we leapt into making our own pigments, using materials as varied as oak galls, spinach, blue flag iris, saffron, and egg shells, among other items.  Each table of three or four participants was in charge of processing a given material.

Oak galls, formed by the larva of a wasp living on an oak tree.

The "oak gall" table had a lot of fun, first smashing the oak galls with a hammer, then grinding them finely using a mortar and pestle. When boiled and mixed with ferrous sulphate, the tannic acid in the oak gall makes a black liquid; the addition of gum arabic to this solution makes a usable ink. Get out your quill pens!

Smashing oak galls.

Another pigment prepared using the mortar is cochineal, made from the carapace of an insect from Central America. Chemically, the pigment is carminic acid; when cochineal powder is precipitated with alum, then mixed with chalk (calcium carbonate), the resulting sludge can be dried, reground and used for purple-y pinks.

Center, a bag of dried bugs; right, a jar of processed cochineal.

Less exotic in its source material is the white pigment made from ordinary hen's eggs. The shells are first soaked in vinegar, so that the inner membrane can be removed, then the shells are crushed on a marble slab, using a muller, the marble cone-shaped thing in the image below.

Eggshells ready to crush.

Eggshells reduced to fine powder.

You may have noticed the vase of iris in the first image above.  This was not just a decorative touch for the classroom - the iris petals were macerated in the pestles and  the resulting pulp pressed through damp coffee filters into small plastic vials. The addition of a small amount of alum creates - not purple as one might expect - but green!  Green pigment can be made using the same macerate-and-strain technique on spinach; no alum required.

Iris petals mashed and strained.

Once we had our pigments we needed the binder - the "glue" that will hold the pigment onto the paper or parchment or whatever substrate is used. Before the invention of oil paint, a common binder was egg yolk - the combination of pigment and egg yolk makes tempera paint, which enjoyed a revival during the Pre-Raphaelite era and is still used by painters today. Below, Jessica shows us how to process eggs to remove the white as well as the vitelline membrane from the yolk, as the blastoderm, the egg white and any membrane are undesirable for paint-making.  Once we had our egg yolk, we mixed it with a bit of water. 

Jessica and egg yolk.

Below are our palettes with the natural pigments we fabricated - the spinach, cochineal, saffron - as well as additional pigments Jessica supplied, such as red and yellow ochre. To each little cup of pigment we added a bit of the egg-and-water mixture. At last, ready to paint!  One suggestion I would make to anyone taking this workshop is to order some paint pot strips and use these in class; when sealed the tempera paints last a long time and then one can take them home and work in the comfort of one's own studio.

Paint palette.

The Met supplied illustration board and transfer paper and using these we transferred images Jessica had provided or just drew our own free-hand. Then, using the provided brushes, we began to paint. The tempera dries quickly, so by the time we had cleaned up our work stations, we were able to pack up our artwork, after a very busy day.

Hard at work.

A talented student's work, from a previous class.