Brief history and preparation of canvas for oil painting
Today, canvas is most common medium for oil paintings. However, was this always so? In fact, it wasn't. Before the Renaissance period (approx. 1400-1700) all paintings were done on more solid mediums, such as wood. However, during time of Italian Renaissance, merchant shipping industry was booming, and with that boom came many innovations and technologies borrowed from more eastern cultures. Among these technologies was use of canvas sail.
Canvas was originally made out of hemp. In fact word 'canvas' originally derived from the Arabic word for 'cannabis,' a Latin term translating to 'hemp' (this is also the name of family of plants from which hemp is made). This strong material was made by tightly weaving the cannabis fibers together. The result was a strong fabric that could be used for sails and tents.
With sudden success of the merchant industry, canvas became readily available to public. Canvas was probably first used by portrait artists in Venice around 1500 AD. Canvas quickly took popularity over more traditional and cumbersome wood planks. Because of its durability, canvas was able to withstand both the paint itself and test of time. Not to mention canvas is more portable, less expensive, and easier to create correct size. No longer was an artist inhibited by the size of wood plank he could find, and much larger paintings resulted from this freedom.
During late 18th and early 19th centuries American cotton had become more readily available and popular for the European artist. Yet artists still preferred the stronger linen or hemp for their oil paintings, despite higher cost. At time cotton fibers were weaker than either linen or hemp. Especially true when cotton was wet, it tended to be more prone to mildew. Only within last hundred or so years has advancing technology finally brought cotton canvas to a position of superiority over linen and hemp.
Preparing Canvas for Oil Painting
Modern canvas is made from cotton, linen or synthetic material. In its natural, unprimed state, cotton canvas is an off-white color, and finer linen canvas is a light brown. Both can be purchased in varying weights and qualities, are the least expensive to buy, but most time-consuming to prepare. It's also possible to buy primed, non stretched canvas, as well as canvas panels, which are already primed, and ready to paint on when purchased. There are also non-stretched canvases available in arts and crafts stores, some office stores, and department stores.
In preparation for a painting, canvas is first stretched and secured over a wooden frame. When stretching your own canvas, four stretcher bars and 8 keys are needed to get a proper stretching. Stretcher bars come in ready made sizes from eight inches to forty eight inches. For canvas longer than 20 inches a mid bar is recommended and for canvas larger than thirty inches, heavier duty stretcher bars with cross panels are recommended. The keys usually come with stretcher bars and help to hold canvas more securely in place at corners. The artists hammer is used to join bars and heavy duty staples are used to secure canvas in place. Canvas pliers are used to grip tightly the canvas during stretching process and a right angle is necessary to be sure that the final product is perfectly square. The process is a little more time-consuming, but in the long run will save the artist money in art supplies.
The surface of canvas then receives a smooth coat of white calcium sulfate, plaster of paris, sealed with a glue, known as gesso. This is to seal the canvas and prevent fibers from absorbing too much of the paint. This coating of gesso is generally followed by pigment lead white, which secures upper pigments. Without this priming, fibers of the canvas would soak up paint and create a 'stained' appearance. Some modern artists actually prefer this look and use unprimed canvas for painting.
