Today artists can buy pre-made mixes of liquids that are often added to paints to acheive a variety of painting effects, increase flow, transparency, viscosity, and increase the luminosity of the paint layers. Some make the paint dry faster, others slower. Many mdeia make the paint look very glossy. Many modern painting media are synthetic petroleum products, but in the past a large number of natural tree resins, fossil resins, waxes, plant oils, and essential oils. Various recipes still exist for making complex painting media in the studio, or pre-made media can be purchased.
A chief binding medium of dry pigments, and ingredient of many varnishes and painting media. Plant oils that dry (oxidize) upon contact with air, and harden into a paint film, are useful for painting, while oiles like oilve oil cannot be used because they never harden.
- Linseed oil - very common, may darken slightly over the decades, but can be lightened in the sun. Refined linseed oil dries more slowly and tends to yellow; sun-thickened linseed oil dries faster and holds brushstrokes well, increasing viscosity; stand oil is boiled and thickened linseed oil, which leaves no brush-marks and is excellent for glazing and glossiness, used in Europe since the 15th Century.
- Poppy oil - good for painting, flows better and more liquid than linseed oil. Dries more slowly than linseed oil, has a buttery effect and holds brushstrokes well. Known from ancient times. My favorite.
- Walnut oil - commonly used, yellows less and dries more slowly into a more flexible film than linseed oil. Does not lighten in the sun. Much favored in Renaissance Europe.
- Hempseed oil - occasionally mentioned in historic sources as a binder, but minimally used in varnishes and binding media.
Also called Essential oils, these include distilled plant liquids and refined petroleum products used to thin paint, lossen consistency of media, and clean brushes.
- Turpentine, spirit of turpentine, balsam distillate - an essential oil, distilled pine, larch, or fir resin, known in ancient times. Makes paint dry faster by evaporation, but the fumes should be taken into account and the studi should have air-circulation hoods with fans to protect the artist. Use sparingly in the painting layers as it can weaken adhesion.
- Turpenoid Natural - by Weber, a good non-toxic alternative to turpentine and mineral spirits made from organic ingredients, that can be used as a thinner, painting medium, and brush cleaner.
- Mineral spirits - many widely available modern petroleum distallates can be used as thinners and solvents. Odorless mineral spirits are popular today, and in the past Naptha was used - petroleum distillate or "rock oil," "white spirits." Dries more slowly than turpentine, but safer.
- Spike of Lavender - a distillation of the essential oil of lavender. Not widely used today. Used as a diluent in the 14th Century in France.
- Alcohol - not for use with oil paints, but sometimes used to dissolve such art supplies as hard shellac pellets or sheets (as a good coating for paper to paint on).
Historic oil painting varnishes consisted of a drying oil plus one or more gums, resins, or balsams. Other varnishes were spirit-based, by dissolving gums and resins in a solvent base. Varnishes increase brushability, enhance the optical effects, and seals colors from wear and tear. Historically, fugitive pigments that darken in air, such as Verdigris, Malachite, and Azurite, were sealed by adding varnishes, retaining their color. Special varnishes were also used to coat intermediate paint layers after they dried, then painted over to produce transparency and glow. Final varnsihes had different recipes to make a hard protective final coating over the finished dry painting.
Soft Resins and Balsams:
- Mastic - resin of the Greek pistachio tree. Mastic varnishes were commonly used in the 18th and 19th Centuries in European painting.
- Pine resin - a historic material not commonly used today. Also called Terebinthina, Colophony.
- Venice turpentine - a crude turpentine of balsam from the larch tree. Often called "Common varnish." Venice turpentine plus turpentine can create fluidity and clarity, said to have been used by Reubens. Good for detail work.
- Strassburg turpentine - pine or fir balsam.
Slightly Harder Resins:
- Sandarac - gum of a cedar from Morocco. Often used by Renaissance and Baroque painters, as Vernice Lquida when mixed with a drying oil.
- Frankincense - gum from a tree in the Middle East, also used as incense.
- Juniper gum -mentioned by Leonardo da Vinci as a substitute for Sandarac.
- Amber - fossil resin of Tertiary conifers (millions of years old). The ancients collected and traded these beautiful substances from the Baltic, and they were called Electrum or Glassa. A long complex heating process in solvents is required to liquify these hard resins into a painting medium, and many researchers credit the beautiful glassy luminosty of these varnishes for creating the effects of many Renaissance masters. Historically these varnishes were also used to coat violins and other musical intruments (Stradavarius had secret recipes). Many modern recipes exist to try to recreate these historic media.
- Copal - somewhat sofeter than amber, these resins come from living trees or fossil deposits. Sources include Africa, New Zealand, India, and Manila, mentioned since 1659.
- Megilp - also called "painter's butter" or Maroger medium, a controversial recipe said to be the secret of the Van Eyck's technique. Popular in the 19th Century as a mix of mastic resin and linseed oil.
- Modern synthetic media such as Gamblin's Galkyd, and Winsor-Newton's Liquin, can also be used to good effect.
- Wax - historically media mixed with beeswax were used to hold brushstrokes for texture. Today synthetic gel media are used too.
- Damar varnish - historic resin varnish.
- Alkyd varnish - popular today, synthetic.
^Various painting media, including my own recipe.
^Painting media from various recent manufacturers.
^Soluvar final varnish, glossy and very weather-resistant. A superior choice for protecting the finished painting.
^Varnishes, store-bought and my recipe for Damar varnish. Some are designed to isolate intermediate layers of the painting when dry, to be painted over. Others are tough final varnishes.