What does a Varnish do for a Painting?

The varnish layer plays a dual role: it has and effect on the final appearance of the painting and also serves as a protective coating for the paint surface.   Varnishes intensify the appearance of pigments on the painting surface by the refraction of light.  This is called "saturation."

Although varnishes are traditionally clear, they can be toned or altered with the addition of pigments and other materials.  Toned varnishes may be utilized to balance a painting whose appearance has changed with age.

What is a Painting Varnish?

Varnishes are solutions of natural or synthetic resins in organic solvents that dry when spread thinly on a surface.  The dried films are solid and relatively transparent.  According to the composition of the solution, the films exhibit varying qualities of gloss, protective ability, flexibility, and durability.

The variety of varnishing materials is as diverse as the choices of paint media and techniques throughout the history of painting.  The benefits of using a clear resin as a final coating for a surface were realized during Antiquity; waxes, for example, have been found on the surfaces of ancient wall paintings.  By the early Renaissance, a variety of materials had been developed for use as painting varnishes, ranging from egg white to resin.  Tree resins (mastic and dammar), fossil resins (copal), and insect excretions (shellac) eventually became the types of materials most frequently chosen for use as varnishes.

Many of these natural materials are still in use today by artists and restorers.   Numerous synthetic varnishes have also been developed that provide a wide array of surface characteristics.  Synthetic varnishes have been popular, however, they do have different properties than natural varnishes.

Does the Varnish Layer Ever Change?

Natural varnishes tend to darken and discolor with time, necessitating their removal and replacement.  The removal of a varnish layer requires great skill and knowledge and should only be undertaken by a trained paintings conservator.

The replacement of a varnish in also not a simple matter.  Conservators must decide whether to replace a natural varnish with another natural varnish, knowing that the natural varnish will yellow and will have to be replaced, or with a synthetic varnish, which may not yellow as rapidly but also may not duplicate the aesthetic effect of the natural varnish.  The skill of varnish application has a great deal to do with the final appearance of the painting.

To Varnish or Not To Varnish?

In many oil painting for the 20th Century, the effect desired by the artist is a matte or unshiny surface.  Paintings without a varnish layer collect dirt in the interstices, which can rarely if ever be removed without damaging the paint layer.   It has been suggested to display or store these works behind glass or in a dirt controlled atmosphere or, alternatively, to possibly compromise their appearance with the application of a varnish.

There are concerns as to whether or not to varnish acrylic paintings and many artists insist that their acrylic paintings be unvarnished.  Acrylic resin proprietary varnishes have similar solubilities to those of acrylic paint.  This necessitates the use of solvents which might damage the paint layer for their removal.  Acrylic paint is also soluble in the solvent used to remove traditional varnishes.  Thus, varnish application to an acrylic painting requires serious consideration.

What Else Protects the Painting?

When a painting is being moved about, a frame will protect the sides.  A frame should be large enough to receive a painting and permit it to be keyed out when necessary.   It also should be in sound condition.

Frames can display paintings with or without a protective glass covering.   Ultraviolet filtering glass is sometimes placed over the painting to protect the painting surface from harmful ultraviolet light and also from dirt and fingerprints.   Although a sheet of glass definitely protects the surface of a painting, it also changes the appearance of the painting.  The aesthetic effect of a glass covering should be considered along with its protective qualities.

Who Can I Turn To?

If you have any questions about your painting, a paintings conservator can help you.   Paintings conservators are professionally trained individuals with years of experience.  You should solicit the advice or services of a conservator any time that you have questions or concerns regarding a painting.  They can help you with the general upkeep of your paintings (dust and grime removal) as well as handle any unfortunate mishaps (paintings that fall from their hooks, fire, flood, insect damage, etc.).

Selected Bibliography

Carr, Dawson W. and Leonard, Mark, Looking at Paintings: a Guide to Technical Terms, Malibu, CA: The John Paul Getty Museum, 1992.
Gettens, Rutherford J. and Stout, George L., Paintings Materials, New York, NY: Dover Publications, 1966.
Gottsegen, Mark David, The Painter's Handbook, New York, NY: Watson-Guptill Publications, 1993.
Keck, Caroline K., A Handbook on the Care of Paintings, The American Association for State and Local History, 1965.
Keck, Caroline K., How to Take Care of Your Pictures, The Museum of Modern Art and The Brooklyn Museum, 1954.
Stout, George L., The Care of Pictures, New York, NY: Columbia University Press, 1948.
Thomson, Garry, The Museum Environment, 2nd edition, Boston, MA: Butterworths, 1986.