In the quiet sanctum of art galleries and private collections, paintings bear witness to the passage of time. Yet, as the years weave their stories into the very fabric of these masterpieces, the varnishes that once protected them from the world begin to show signs of wear. The once brilliant colours fade into a muted symphony, and the owner, recognising the whispers of aging, will turn to me as an art restorer with a plea to revive the canvas or panel to its former glory.
The Ideal Varnish: An Art Conservator’s Dream
For those of us who are art conservators, the ideal varnish is a rare alchemy—a potion that would remain transparent and colourless over time, retain adequate elasticity, protect the paint beneath it, and allow for a gentle, nonpolar solvent removal. In the juggling act between tradition and innovation, finding this elusive elixir becomes the cornerstone of our craft.
The quest for this perfection dates back centuries and continues even today. The range of options for the art restorer grows bigger with every generation. When I assess the condition of a painting, the nature of the surface damage and the condition of the colour can often be attributed to the choices of varnish made by the original painter and by subsequent art restorers.
Frequently the varnish will have to be removed so it’s vital that I determine what that varnish is so that I can use the appropriate technique to remove it. And at the end of the restoration process I will want to reapply a varnish – once again drawing on the range of options to choose one that is most suitable to protect the painting and to do justice to its optical qualities.
Varnishes can be divided into organic and synthetic. Within both groups there are different products each with very different profiles. My job will always be to balance the pros and cons of each option within the context of a specific painting.
Natural Varnishes
Oil and Oleoresinous
These natural varnishes include linseed and walnut oils, and they usually require an additive to speed up drying. Their main drawback is the speed and degree with which they turn an unappealing brown, obscuring the colours and nuances of the painting. Whilst I would never reapply an oil or oleoresinous varnish, it is not uncommon to encounter canvases or panels whose cleaning will require the removal of this type of varnish. This can be a delicate and time-consuming process for the art conservator.
Albumen/Egg White
Crafted from egg whites, water, and honey, albumen varnish, unfortunately, induces shrinkage and craquelure in the paint surface. Its brittleness and light-induced insolubility make it a less-than-ideal choice for restoration, and an artwork that has been varnished with albumen may need a fair amount of retouching to deal with the extensive craquelure.
Natural Resins
Natural resins, notably damar and mastic, have been used historically and I will likely encounter them in any painting that has been varnished before the 20th century. These soft resins turn yellow over the years and form a network of cracks, reacting to moisture in the air as they mature.
Alcohol
These varnishes are prepared by dissolving a natural resin in ethanol. I would consider using it as an insulating layer in cases where I am struggling to get a consistent effect from the reapplied varnish. Varnished surfaces that suffer from ‘impacted’ damar will often appear matt in certain areas and shiny in others. The ethanol and resin layer mitigates this effect and then the final coat of damar varnish can be applied.
Laboratory-Made Varnishes
The disadvantages of these natural resins have motivated many generations of scientists to create a synthetic solution that gets closer to the art conservator’s ideal varnish.
Synthetic Resins
PVAC (derived from polyvinyl acetates) was one of the first of these on the market. These varnishes are more stable than their natural counterparts but they have an unfortunate tendency to remain tacky and to mute the intensity of the painting’s colours.
The next effort involved creating acrylic resins and Paraloid B72 is one of these that most art conservators will have encountered. Regrettably , acrylic resins are not all that stable and they fail to restore the depth and luminosity that one expects from Old Masters.
Next up were the ketone resins like Laparol K80. While initially effective,they tend to become brittle and detach from the paint surface over time, giving colours a muted, grey appearance.
Hydrocarbon resins have also been devised and, with their low molecular weight and softness they seem to be one of the more promising synthetic options.
A relatively new contender, aldehyde resin demonstrates stability and solubility in various solvents. From the 1990s some art conservators have been using it to varnish paintings that they have restored.
As you can probably glean, we are far from achieving that varnish elixir. There is a growing consensus among art conservators, myself included, that it’s best to use materials that are as sympathetic with the original and as natural as possible. However, when I complete a restoration project with a final coat of damar varnish I have to make the client aware that the resin will yellow with time and that it will need to be cleaned again in 50, 60, 70 years….
There can be no default procedure when it comes to treating a painting. It is my job to consider a range of parameters, some of which can be competing and include the environment in which the work will be stored; the agenda of the client; the reversibility of any work; and the preservation of the original.
At my fingertips I have access to tradition and innovation allowing me to choose the path that is most beneficial to extending the life of your painting.