Canvas can be easily damaged by impacts and is very reactive to humidity, expanding and contracting as the weather changes. When canvas ages it becomes more delicate as fibers lose their elasticity. Historically lining, which involves the removal of the painting from its stretcher and adhering it to a second canvas, has been the typical treatment used to repair damaged canvases. This method introduces a new level of strength and stability to the painting, correcting distortions and repairing tears. The traditional method of attaching a lining was to use animal glue and hot hand irons. When expertly done this technique achieved positive results, however in the past, crude linings have done as much harm by burning or flattening paint-layers and unfortunately much of the damage to paintings uncovered by conservators today is a result of poor attempts at lining.
Traditionally the lining of canvas paintings was an almost routine stage in the restoration process and it is quite unusual to find a painting older than the nineteenth century that has escaped this process. Some of the works in the National Gallery’s collection that remain unlined are The Marriage of Strongbow and Aoife by Daniel Maclise, The Arrival of the Kattendijk at Texel by Ludolf Backhuysen and much of the Irish school including works by Ashford, Roberts and Barret. The clarity of a painting’s surface that is unlined can be strikingly different, fortunately many of the Gallery’s key impressionist works such as Argenteuil Basin with a Single Sailboat by Monet, Van Gogh’s Rooftops in Paris and Morisot’s Le Corsage Noir are also unlined.
Despite its history, lining is sometimes still required to stabilise a damaged painting. Nowadays conservators undertake lining treatments in a controlled manner using low pressure suction tables, which works by gently holding a painting against a finely perforated surface and controlling exact applications of humidity, heat and pressure. The availability of this type of control allows a painting to be treated with minimal pressure enabling the repair of badly damages paintings without the negative drawbacks of traditional lining techniques.
Read about repairing the canvas of The Marriage of Strongbow and Aoife