GAMBOGE

A gum resin pigment much used in watercolor, which is neither lightproof alone or when mixed with other pigments. In thick layers it shows a gloss because of its resin content, and as an oil color it strikes through, therefore being unusable. It burns with an odor of resin, is poisonous, is not attacked by acids, and turns red in alkalis.

GIALLORINO - MASSICOT

The other medieval yellow used mostly in Italy which may have been of mineral origin, was giallulinum, the little yellow, a diminutive of giallus meaning "yellow". Some fourteenth century texts say that Mount Gilboa is green on one side and yellow on the other, a reference more likely attributed to orpiment. Cennino say that this giallorino is half natural and half artificial, found in nature as a stone in places volcanic. There is a legend that a bright yellow mineral used to be found in Naples, a product of Vesuvius, which gave its name to Naples yellow. Also a potter's color for yellow glazing compounded from lead and antimony, was known as giallulinum, which was used by painters at some point, it has been suggested was an artificial imitation of the extinct volcanic stone once found at Naples. There is a bit of confusion over all of this. Most medieval references to giallorino mean massicot, a yellow oxide of lead, prepared in the Middle ages by roasting of orange lead, the intermediate product in lead white. This pale but fairly intense yellow known in classical antiquity was too attractive to have been overlooked by medieval painters.

GRAPHITE

A form of crystalline carbon that is available naturally as a mineral in many parts of the world (modern source is Sri Lanka) and has also been made artificially by furnace process since 1891. It has been long used as a writing material, which is why the confusion with lead, hence the names "black lead" and "plumbago"; the name however is from Greek, meaning "to write". In pencils it is compressed with fine clay, and otherwise has a greasy texture and is a dull gray, being seldom used except in mural painting. It is permanent in all techniques, but has a tendency to strike through. Bocklin used in the frescos at Basel. As a further note however, I worked with graphite for many years in paintings, and found the slightly silver tone after drying quite wonderful, especially when rubbed till glowing, and the heavy, inconsistent strokes that it made on brush, wonderful for certain effects that were impossible with any other black pigment. It is however important to note that it is highly toxic, needs to be immediately wetted with varnish or linseed (not advised but I've had great success with it in linseed, as long as it is varnished after, or the oil is heavy enough.) and a fairly large amount in order to liquefy it. It is also best to varnish it after painting as well. It is also highly stable and very reflective, something which can be quite useful in certain techniques. There are references to graphite in fourteenth and fifteenth century texts to the use of a soft black stone, presumably graphite, a soft, smooth natural deposit of carbon, which we're more familiar with as our so called lead for pencils. However from all evidence, in the Middle Ages, when used at all, it was chiefly for drawing.

GREEN CINNABAR

A senseless but commonly adopted name for various green mixtures, among them chrome yellow-green, also mixtures of Paris blue and Chrome yellow.

GREEN EARTHS

There is no physical resemblance between malachite and the green earths which we call Terre Verte, which is in comparison rather dull, transparent, and soapy in texture, like a clay. It is also not constant, ranging from a light bluish gray with a greenish cast to a dark, brownish olive. The name Terre Verte is applied to several different minerals, but most importantly in medieval painting is the light, cold green of celadonite, found chiefly in small deposits in rock in the area of verona, in northern Italy. The chief deposits of glauconite which yield the yellowish and olive sorts are in Czechoslovakia. No effort has been made to distinguish the characters and sources of Terre Vertes in medieval paintings; and if these distinctions were made they could teach us a great deal more. These were not the strong colors; they wouldn't do for painting naturalistic landscape effects, and weren't used to this effect except in wall paintings where the dull tones were in order. In manuscripts and on panels they were chiefly used to underpaint the warm flesh tones. In the fifteenth century liberties were taken with the traditional green preparation for flesh: ochre was mixed with it, or a little black, or stronger green and so on.

In general, especially in works before the fifteenth century, it was quite usual to underpaint flesh with green earths mixed with whites only. They require 100% oil but dry normally. They are not poisonous, dissolve partially with a yellowish-green color in hydrochloric acid, but not in alkalis, and should not discolor water, alcohol or ammonia.. Today the color is chiefly a durable mixture of chromium oxide, black, white and ochre, since the natural product is scarcely obtainable, though possible with effort. The color is excellent in fresco but turns much lighter when drying, and was used a great deal in Pompeii. The glazing Bohemian green earths were often used as undertones by the older Munich school for painting wet-on-wet, and is well suited to this technique as it gives to other colors painted over it a subdued tone. They darken later due to their large oil content, but this makes little difference in a picture planned in a brown key. The cheaper sorts designed for commercial purposes may show rusty discolorations when used in fresco.

GREEN LAKE

Hooker's green, leaf green, sap green are all other names for this pigment, all of which are impermanent pigments composed of Prussian blues and yellow lakes. There also exist green coal-tar colors which are no better.