A client came in last week inquiring about the cleaning of an old painting. Even though what was needed was a ‘simple’ cleaning the client seemed nervous so I found myself giving an hour long explanation about the process and issues involved. It has occurred to me that others may also be interested in this subject as well so without getting bogged down in unlikely scenarios I would like to explain the basic concepts.
The foundation of most paintings is canvas. The canvas can be of different material but most often is linen or cotton which is pulled tightly over stretchers. If any part of that stretcher is touching the canvas other than the very outer edge there may be problems down the road. Fabric tends to follow the form of whatever is below it and this can be the cause of ‘stretcher cracks’ in the paint about an inch or so from the edge. The artist then applies a primer, also known as gesso, to the surface of the canvas which protects the fibers of the fabric and serves as a binding medium for the paint. In the old days this primer consisted of rabbit skin glue, chalk and a white pigment. The use of titanium white in those older primers is sometimes the cause of ‘craquelure’ in old master paintings.
Finally we get to the surface itself. The paint. Oil Paints are essentially ground pigments suspended in linseed oil. After the artist has finished the painting some of the binding medium evaporates and the painting looks ‘dry’. The truth is that the paint is a hydrocarbon which dries by forming molecular bonds, technically called polymerization, and doesn’t truly totally dry for 100 years! Hard to believe. But when the painting looks dry enough the artist will add a clear varnish layer…...which can be anything from a matte finish to a high gloss.
What we see quite often in the restoration business is a canvas that has been varnished too soon which allows the varnish molecules to absorb into the paint layer with the result that the painting still looks ‘dry’. In this case we lightly clean any dirt or dust off the canvas and reapply a new varnish coat. The standard today is to use an acrylic varnish that doesn’t yellow with time and is easily removable if necessary. However, throughout history and up until about 40 years ago, most artists used a damar resin based varnish. Over time damar varnish yellows and the removal of damar varnish is a tricky business. Remember, both the varnish and the paints are hydrocarbons. What is a solvent for one is generally a solvent for the other. A conservator will experiment with a series of solvents, from denatured alcohol to acetone, to determine exactly which one is the right strength.
What about missing chips of paint? This sort of thing usually occurs due to either the canvas getting hit front or back or because of an instability in the gesso and paint adhesion. Most times this can be touched up. The repair will be invisible to the naked eye but can be seen under a black light which will highlight new paint from old paint. Once again, in-painting today is done with acrylic paints which do not change color over time and are easily reversible. Old repairs in old paintings which were done with oil paints are often easy to spot since oils darken slightly over time. Even though the restorer matched the colors originally, after a period of twenty years it doesn’t look the same. If there is extensive cracking in the paint layer, many missing chips, or an actual hole in the canvas, it may be necessary to add an additional canvas on the back side. This is called ‘relining’ and the two canvas are ‘glued’ together with a synthetic beeswax. Additional heat and moisture allows the synthetic adhesive to permeate the top canvas, thereby adhering to and consolidating the damaged paint surface.
Those are the basics. Over the years we have seen many variations of all these operations. It’s not often that the damage or situation is hopeless. Offhand I can only recall one time. We had received on consignment a very large painting by the Kansas artist Birger Sandzen. Apparently, Sandzen had improperly gessoed the canvas because when we opened the box the entire painting lay in chips at the bottom. The movement in shipping had knocked all the paint loose! It was a shock. Fortunately, the owner had the painting properly insured…...but still what a shame. This is why we try to be sure that the contemporary artists we represent in the gallery use archival materials…….no obsolescence here!
If you have any questions about the condition of your artwork please feel free to contact the gallery. Saks Galleries has a national reputation for quality and we stand behind the pieces we sell. We provide art services that we consider to be part of the business of buying and selling fine art.