The First Style is called masonry or incrustation. The Metropolitan Museum of Art explains that this style was used between 200-60 B.C. to decorate the homes of the middle class so that the walls in their homes would resemble the walls in Greek palaces. The style utilized fresco techniques in which either wet or dry plaster was painted to imitate the look of real marble. In the later part of the First Style artists began to represent Greek gods and goddesses in their paintings.
The Second Style began in the early first century. The Thou Art History website indicates that this style is also called the Illusionistic or Architectural Style. It was characterized by the use of approximate linear perspective that created the sense of illusion and depth within wall paintings. The artists of this time period often used trompe d'oeil (fool the eye) techniques to make painted objects look real.
According to the Thou art History and the Metropolitan Museum of Art websites, the Third Style is also called the Ornate or Ornamental style. In this type of painting the frames are painted on the pictures to create the illusion of a visual gallery. These paintings are flat and ornamental, employing monochromatic backgrounds with intricate detailing. The Third Style lasted from 20 B.C. until 20 A.D.
The Fourth Style incorporated elements from the previous three styles. The Metropolitan Museum explains that the large-scale painting of the Second Style and the intricate details of the Third Style were both commonly seen. This era lasted from 20 A.D. to 79 A.D.
The Old Stones website quotes the ancient Roman writers Pliny the Elder and Vitruvius, who described in detail how frescoes were created in Roman times. Lime and sand were mixed thoroughly to create a mortar, and several coats of this mortar were applied to a wall. The mortar mixture was followed by several coats of lime that were mixed with powdered marble. The artist used a paintbrush to apply pigment directly to the wet mortar.
Pigments came from mineral, vegetable or animal based sources. According to the Encyclopedia of Irish and World Art, reds were created using tree-based gum resins and minerals such as mercuric sulfide. Blues could be manufactured from woad or indigo, and yellow was made from lead oxide. Other colors such as burnt umber and burnt sienna were made using clays, while a rich black could be created by burning bones.