Mediums are additives to oil paints used to enhance certain effects, such as translucency and lustre, to produce a glaze or to minimise problems such as drying times.
These are various kinds of oils and solvents that, according to some artists, hold the secret to the works of art produced by the Old Masters. Certainly, understanding how to use mediums is part of the skill of oil painting.
Linseed, walnut, safflower and poppy oils are traditional art materials used as binders for all oil colours. Not only do they dilute the paint but they also produce a translucent and glossy effect when dry. However, these oils increase the drying time of paints and if used excessively, they cause wrinkling on the painted surface. A compromise would be to mix the oil with a solvent in 1 to 1 ratio.
Oils can be applied directly to a surface before painting and wiped with a cloth to ensure a very thin cover. But this should be done only during a painting session since surface oiling will cause yellowing.Solvents
White spirit and turpentine are common solvents used by artist as well as decorators. As well as thinning the paint they reduce the drying time. But they also have a dulling effect. If used excessively they can affect the paint adhesion to the surface and create chalking. The fumes from these solvents also make them unpleasant to use, and they often come in childproof containers that are difficult to open even by adults.
The best way to use solvents is to keep them in covered containers, dip a brush into the solvent just before use and mix it with the paint on a palette. If applied directly to a surface, the solvent will dissolve lower paint layers.
The Old Masters used natural tree resins such as gum Arabic, dammar, mastic and amber to produce a gloss effect. The problem however, was that eventually, the paint film yellowed, peeled and cracked.
Alkyds are synthetic resins that produce the same effects without the yellowing, fading and cracking. Liquin is a modern alkyd that halves drying and impedes yellowing. Different types of liquid mediums such as Liquin Gel, Liquin Impasto, Liquin Oleopasto as well as the Liquin Original are available from Jackson ‘s Art Supplies. The advantages of synthetic resins are that they are available in standard bottles and they do not produce fumes in the way that solvents do.
However, it’s important to remember that liquin is not suitable as a varnish and should be used only as an additive.
Waxes such as beeswax can be mixed with resins to create a medium that adds translucency and gloss to paintings. They also strengthen the painting by sealing out dirt and moisture and help to prevent yellowing and cracking. They can also be used as final coats on metal sculptures as well as paintings. Bleached beeswax is used by candle makers as well as painters to create a matt colour but it does emit fumes when applied so needs to be used in an area with good ventilation.