After an oil painting is finished it benefits from varnish to be in the very best condition. This doesn’t only preserve the paint, but often brings out brighter saturation, ensures it does not become dull and gives the finished product a professional quality.
Varnish is recommended only for oil and acrylic paints, this is because the film which seals the dry pigment is thick and further from the surface. The varnish on an oil painting can later be removed by specialist solvents if needed.
Watercolour or drawings in pen or pencil are not recommended for varnishing, as they are often on porous paper and the paint itself is more absorbent. Varnish on watercolour, drawings, or gouache cannot be easily removed without damaging the artwork.
Varnish has always played an important role in the history of oil painting, during academy exhibitions the artists would be given a ‘Varnishing Day’ before the opening, to ensure all of the artwork was in the very best condition for display. Traditionally, this would have been completed by the artist’s colourmen, the workers who were behind the scenes supplying the canvases, pigments and varnish for great artists.
Gloss varnishes are a popular choice as they bring out the bright tones of the artwork, whilst giving a classic shine. However, if you’d like to avoid the reflective glow from lights upon the surface, these may not be the right fit as they can give off an almost mirror-like effect.
During the 18th century, this flawless finish was highly prized and notably used in the studio of French artists, as an attempt to clear any sign of the artist’s hand or brush strokes from the finished piece. Gloss varnish gave these paintings what is referred to as a ‘Licked Finish’ due to the clean surface it produces. This effect divided the work of professional artists from those seen as amateurs, who could not achieve such a smooth, glowing finish.
Colour may appear a little duller with a matt varnish, but this is a good way to avoid disruption of light reflected on the artwork. Whilst a gloss varnish will make colours such as black appear very deep in tone, a matt varnish may do the opposite and make the depth lift in dark areas.
The later revolutionary brushwork of the impressionists favoured a matt finish, or to go completely unvarnished, in a clear move against the glossed style of aristocratically engaged artists of the past.
Whilst gloss varnish can appear fully transparent and matt slightly muted, satin is a happy medium between the two. A matt varnish can be mixed with a gloss varnish to produce a satin layer which can be then levelled out to the amount of shine you would like on your painting.
Traditional resin vs. synthetic resin varnish
Dammar and mastic are examples of traditional varnish made from tree resin, making them susceptible to natural degradation over a course of time. Damar varnish is made from coniferous trees, whilst Mastic varnish is made specially from the Greek pistacia lentiscus plant. Some can often start off with a yellow tinge due to their botanical ingredients and become far more yellow as decades pass.
Whilst these varnishes are often the traditionalist approach, in antique oil painting restoration and conservation our specialists will use a synthetic substitute. Synthetic resin varnish has not been known to discolour in the same way that a natural resin has been witnessed to and is also strong when it comes to UV rays and further protection against the elements.
A layer of varnish will offer UV protection to your artwork. Specialist UV filtering varnish can offer the best solution to keep your pigments safe from strong sunlight. UV top-coats are also available and are often used at the final stage. If a painting is framed without museum grade or UV filtering glass, it is recommended that these layers of extra protection are taken into consideration.