The gesso ground, because of its qualities of absorbency, white luminosity, and smoothness, is an ideal base for egg tempera painting. This ground is applied in a series of eight or more coatings over the wooden panel.
Gold in icons symbolizes spiritual light. It used on halos, backgrounds, or in assists. The method to apply the gold is called water gilding on the poliment. The bole is a mixture of clean clay, water, and glue made of rabbit skin granules. Double gilding is often used. This produces a higher quality result. Afterwards, the gold is burnished, with an optional decorative pattern in the halo or background traced from paper onto the gilded area.
Icons are painted with egg tempera, which is mixture of egg yolk, wine, and colored dry pigments. When painted on a smooth, white gessoed board, the colors take on a beauty and luminosity of their own.
Byzantine artists developed special methods of building painting in layers, from dark to cooler lighter tones.
During the stages of painting an icon, several different methods of paint application are used. Little lake, "Petit lake," refers to the first application by flooding the paint on the gessoed panel. This is achieved by adding series of adjacent "puddles", which merge into each other. After drying, highlight with lighter colors, allowing each layer dry before applying the next. Finally, a thin, even coating of very diluted or semitransparent colors is painted, creating a "floating" effect.
Modelling the form is not just a matter of progression from dark to light: there are also changes in color temperature, from warm to cool. For example, rose over green.
Line painting is done over the background colors with fine squirrel brushes. The width and color of these lines varies according to the design and colors. The sensitivity and rhythmic flow of these lines is an essential feature of the icon. People often say that an icon is "written".
Final highlights are very fine. Ozhivki or "living futures", refers to the final highlight lines.
Assist are the fine lines in gold over the painted image. This could be done with multiple methods: using transfer gold over painted lines with gold size, by painting lines with "shell gold", or scratching through the color painted over gold. This technique is called "sgrafitto".
In an ideal situation, after a few months, the icon can be varnished. For the matte varnish, a small amount of melted beeswax, is added. The icon could be varnished with clear shellac.