The ground is the layer that physically separates the oil paints from the support. It acts as a barrier between the two, providing a surface that is chemically stable and takes the paint properly.
In perusing the catalogues of discount art supplies, it's worth bearing in mind that three types of ground are used in oil painting.
1. Acrylic. Tins of acrylic primer can be bought at most art stores. Or boards, panels and canvases purchased already so treated. Most experienced painters shun them, but they have so far (in 40 years) given no cause for concern.
2. Aqueous-based gesso. This uses some white material (gypsum, plaster of paris, zinc or titanium whites) held together by animal glue. Gelatin or cassein are generally used for tempera, but can be used for oil painting, particularly for that needing detailed underdrawing of the Pre-Raphaelite type approach.
3. Oil-based grounds are like gesso, but use oil in place of the animal glue as a binder, often with siccatives to improve drying.
The boards, canvas or panels need to be properly primed, taut/hard and dry. Whatever the ground, the primer is applied in much the same way. For aqueous-based gesso:
1. Follow the instructions on the tin to prepare an adequate quantity of slightly diluted geso.
2. Select your brush: an old 2" house-painting brush is best, but make sure it's of good quality and will not shed hairs.
3. Wet the brush and squeeze dry.
4. Paint the surface with a single coat of gesso, brushing the gesso thickly and stiffly into the grain of the canvas in a rapid and even fashion. Lay on this coat in one direction of the canvas grain, either parallel to the width or length of the canvas.
5. Clean the brush immediately with household soap and water.
6. Allow surface to dry: generally for an hour or more.
7. Very lightly sand the surface with a a fine glasspaper to remove bumps and canvas threads, wiping surface afterwards with a damp cloth.
8. Wet the brush as before.
9. Apply a second coat of gesso, in the same manner as before, but now in a direction perpendicular to the previous.
11. Clean the brush thoroughly.
12. Allow surface to dry.
13. Sand lightly as before and wipe clean with a damp cloth.
14. Repeat the procedures for two coats on the canvas wrap-around to the sides and back of the stretcher.
15. Allow primed canvas to dry thoroughly: some weeks usually, particularly for oil-based primers.
To improve the painting surface of cheap, ready-primed canvases that feature in discount art supplies:
1. Lightly sand the surface with a fine glasspaper, and wipe clean with a damp cloth.
2. Apply one or two coats of gesso as above.
Fiberboard can soak up enormous quantities of size and gesso primer before a really smooth surface is obtained. One solution is to use an acrylic primer, and a second (better) is to use Golden gesso.
Smooth, brilliant surfaces needed for photo-realism or work of great detail can be prepared by:
1. Sizing a fine linen canvas, and
2. Applying as many coats of glue-based priming as are needed, carefully sanding down between the coats. (Acrylic tends to give too rubbery a surface, and multiple layers of white, oil-based gesso may crack.)
Most painters now start on a white ground, applying a very thin, turpentine-diluted wash of ochres or umbers to provide a neutral, medium tone on which to begin work. You can also mix or replace the titanium whites in the gesso with other pigments to start with a canvas that already has an attractive gray or brownish tone.
Discount art supplies will supply ingredients. Canvas preparation is a straightforward matter, but these may help:
1. 'Types of Gessoes for Oil Painting'. Rachel Shirley Paintings. One of many helpful pages.
2. Preparing a Painting Support. Golden Artist Colors. Brief but comprehensive coverage.
3. Excerpts from 'The Definitive Guide to Artists’ Materials' by Steven Saitzyk (1987) Art Hardware. Includes older approaches.
4. 'The Artists's Handbook of Materials and Techniques' by Ralph Mayer. 5th Edition. Viking Press. 1991.
5. 'What Every Artist Needs to Know About' by David Pyle. Krause Publications. 2000.
6. 'The Materials of the Artist and their Use in Painting' by Max Doerner. Harvest Books. 1984
7. 'Formulas for Painters' by Robert Massey. Watson-Gupthill. 1980.
9. 'The Materials and Techniques of Painting'. J. Stephenson. Thames & Hudson. 1989.
10. 'The Artist's Methods and Materials'. M. Bazzi. John Murray. 1960.
'The Huntsmen's Picnic 'by Gustave Courbet. 1858. Wallraf-Richart Museum. Cologne. Typical Courbet earthy, blunt but vigorous handling, and a simple color scheme.