Since the early Renaissance, artists working on portraits in oil (or any other subject for that matter) have always started with a layer of size to seal the raw canvas or board prior to the gesso ground. It’s job is to protect the canvas from the chemicals in the paint that may cause it to break down. Today, if you use an acrylic primer, size is not always required, but it’s remains a good way of protecting the canvas and if you make your own gesso is an important part of the preparation. It can also be a useful additive when preparing water colour grounds, as it helps reduce absorbency for works where great detail is required, or where it is preferable for the colour to have a better flow over the surface. For the artist, size is something that is easily and cheaply made:
Preparing size
Size is created from animal glue or gelatine and water. One part glue in fifteen parts of water is the correct strength to use on canvas. If you want to apply size to a panel you should use one part glue to ten parts water. Firstly, put the dry glue and water in a heat proof dish that will conduct the heat well and leave it to stand. Depending on how large the particles of glue are it may take anything between half and hour to six hours for the glue to soak. Wait until the glue has taken up some of the water and has become soft without actually dissolving. You will now need to place the dish in another larger heat proof dish that will allow boiling water to be poured between the gap. This should provide sufficient heat to finish melting the glue and create a pure liquid. Stirring will help it dissolve quicker. Once it is totally melted the size solution is ready to use.
Tags: art, artists, oil painting, portraits, size