Orpiment
Composition and Properties of Orpiment
Orpiment is yellow arsenic sulfide with the formula As2S3. It occurs naturally as a mineral and can also be prepared artificially.The pigment is not very stable and decomposes slowly in contact with water, it is, however, more stable when dry. It is considered fairly lightfast but it can in some cases darken considerably and it is not compatible with lead and copper pigments.
Names
King’s yellow, yellow arsenic sulfidePY 39, CI 77085 and 77086From Latin auripigmentum, from aurum “gold” + pigmentum “coloring matter, pigment, paint,” from stem of pingere “to color, paint,”From Online Etymology Dictionary
Preparation
Attention: Arsenic compounds are toxic and should not be handled by people not trained to do so.The mineral has to be broken, ground and purified.Preparation of artificial orpiment The pigment can be prepared by heating and subsequent sublimation of a mixture of sulfur and arsenic oxides.
History of Use
It has been in use since antiquity until about the nineteenth century. The following graph gives the frequency of its use in the paintings of the Schack Collection in the Bavarian State Art Collections in Munich (1).Examples of use
Quote
The two oxides [cuprous oxide & cupric oxide of copper were used in glass-making; verdigris was manufactured and put to several uses; white lead was used as a cosmetic by the Athenian ladies, and found further use as a medicine; red lead was used as a paint; stibium, or native antimony sulphide, was used as a paint for the eyelashes, and is still used for that purpose in the East under the name of kohl; black oxide of manganese was used in glass-making, especially for clearing up darkened masses, and so got its name of pyrolusite; the native carbonate of zinc was also known and used; the sulphides of arsenic, orpiment and realgar, were well-known pigments.
Source: A Short History of Chemistry
Gainsborough's Palette. - This I had from Mr. Briggs, but have lost it; still, as I have copied several Gainsborough's, I think I can furnish you with it. Yellows: yellow ochre, Naples }nllow, yellow lake, and for his high lights (but very seldom) some brighter yellow, probably some preparation of orpiment, raw sienna. Reds: vermilion, light red Venetian, and the lakes. Browns: burnt sienna, cologne earth (this he used very freely, and brown pink the same). He used a great deal of terra verte, which he mixed with his blues, generally with ultramarine. His skies are ultramarine. In his early pictures I could never trace other colours. pp. 63-64
Source: Thomas Gainsborough
