Varnish Research and Experimentation
The importance of a varnish layer on an original oil painting is more complex than just a protective finish. Although we desire paintings to be properly protected from the elements, it is equally important to consider how the finish layer will react with the pigments and substrates over time, the aesthetic qualities of the finish, and how this finish relates to artwork throughout history. There are an immense variety of varnishes available on the market today. Since the 19th century, dammar resin has been the most used resin for varnishing oil paintings. It is a natural resin, highly protective and long-lasting, but is difficult to remove without the use of heavier solvents. Many artists still use it today to varnish their paintings. Dammar produces a high gloss rich finish, but it yellows with time. Although this reflective sheen can be rubbed to produce less glare, it is not ideal for restorative purposes. The majority of conservation specialists use different removable varnishes for these reasons. It is fundamental in any conservation work that everything done to conserve an artifact is not only reversible but accurate to the artist’s original intent.
In most conservation grade varnishes there are multiple key components to the mixture that provide long-lasting adhesion, protection from the elements, and produce the desired sheen. There are multiple resin bases that are used in removable, conservation grade varnishes. Laropal, Regalrez, Dammar, and Paraloid B-44 are the most commonly used. They each have unique properties. A UV stabilizer is added to each of these resins to ensure protection against the elements. Currently, larapol based varnishes are known to be the most stable. It is also used as a medium for conservation pigments in restoring paintings. This resin can be used as an isolating layer or a final varnish layer. It has a satin, even sheen making it an ideal varnish for most lighting environments.
Regalrez varnishes produce a colorless, protective film that will not yellow for over 100 years. It has a gloss sheen and can be rubbed similarly to Dammar. This resin can be removed easily without harsh solvents. Acrylic Based varnishes also produce a colorless, protective film with an even, satin finish. This acrylic resin can easily be removed without harsh solvents.
Today there are a variety of varnish options to choose from. It is important to consider the positive and negative attributes of these resins individually when considering what finish will suit a particular painting. For instance it is primary to consider the materials that the varnish will be covering. If the artwork is more fragile or vulnerable to solvents a varnish that is more easily removed may be the best option. For all of these reasons, a varnish layer is to be considered much more than just a protective coating.
