The Known Unknown

The field of art conservation includes some knowns. Paintings typically accumulate an appreciable layer of dust and dirt over a few years, especially if they are situated near fireplaces or raucous dining halls. We also can rely upon the yellowing and embrittlement of varnish, notably on paintings that possess a natural resin varnish like dammar (a type of resin derived from the tree family Dipterocarpaceae). Finally, we have well-researched methods of safely unpacking these layers from works of art and even new methods like gels and nanofluids that add to the conservator’s tool chest. For the vast majority of paintings, the response to our actions is predictable, especially after comprehensive testing and a cautious tempo. Some people may say meditative. Calming. Almost tranquil.

And then comes the rapid and stunning arrival of the unknown.

One such unknown event occurred several years ago in the paintings conservation lab at ROM with the painting Fishing Station, Newfoundland by Gerard van Edema. Known as the Salvator Rosa of the North, the Dutch born Edema reportedly travelled on ships to places like Newfoundland, New York, and Surinam, painting landscapes for later display in affluent European interiors. During the standard removal of a varnish on this circa 1690 landscape painting, the ROM conservation team used a standard solvent (from the alcohol family) with a standard technique (delicately rolling a dampened cotton swab). Inexplicably, a phenomenon started to appear on the surface of the painting. A once-saturated and rendered image of trees and sky became parched and undefined. A porous brown haze was cast onto the verdant foliage, and the light blue sky was invaded by reddish-mauve-brown fog.

Quelling panic, the team immediately brushed the surface with a temporary varnish, and the colours generally returned. But what caused this very unusual effect? 

The team took paint strata samples from various locations on the painting, derived from areas that possessed different colours and different appearances, and sent the samples to the Canadian Conservation Institute for analysis. The analysis aimed to determine the pigments used by the artist, the binder used to keep the paints together in the dried paint film, and any other varnishes, coatings, or additives that would help shed light on why this phenomenon occurred in the painting.  

The verdict: the cause of this unusual phenomenon rests with a medium-blue pigment particle known as smalt. Smalt is a potassium silicate glass coloured by cobalt ions and is a blue pigment found on 16th- to 18th-century painters’ palettes. An unstable pigment, it is prone to degradation due to a leaching of potassium from the glass resulting from reactions with the surrounding free fatty acids, causing the once-blue glass to turn transparent. Other chemical reactions can occur, resulting in a crust formation, which then inspires restorers to clean off the crust. This kickstarts another round of deeper degradation, resulting in the formation of more transparent pigment particles.  

The blue in the sky of Fishing Station, Newfoundland is entirely smalt. As the blue is now absent from the transparent particle, the viewer is left with a clear rendering of the reddish-brown priming layer. Previous art restorers no doubt had similar rapid and stunning events with this painting during their cleaning campaigns, which resulted in broad overpaint applications of more recent blue pigments such as Prussian blue, which didn’t exist in the late 1600s. Prussian blue was accidentally discovered about 15 years after Edema created Fishing Station, Newfoundland and is considered the first modern synthetic pigment.  

Guided by the results from the Canadian Conservation Institute, Stephen Gritt was assigned the painting’s restoration. Gritt is a senior conservator from Ottawa who is in private practice, and his task was to focus on removing old varnish and overpaints and then on reintegrating the leached and damaged areas. This involved not a heavy-handed swath of new paint but rather localized and minute additions of removeable retouching so that the viewer can better interpret the painting. Of utmost importance was the correct rendering of the rocky midground, formerly hidden by copious green overpaint. This new rendering of the midground is much more akin to the coastline of Newfoundland that Edema initially depicted. 

Until 2028, ROM is pleased to loan this painting to The Rooms, the provincial museum, archives, and art gallery of Newfoundland and Labrador, which is located in downtown St. John’s. Fishing Station, Newfoundland is displayed amongst other early depictions of Newfoundland in an exhibition entitled Newfoundland Imagined: European Visions in the 1600s. In the exhibition, viewers are invited to provide possible locations of Edema’s landscape, as well as of the adjacent painting: an outward-facing coastal landscape attributed to Edema.

Heidi Sobol is Senior Manager, Conservation at ROM.