Supports & Grounds for Painting

Many people confuse the terms support and ground.  In fact, the two often are used interchangeably.  It is important to make a distinction.

Support A support is the surface, the backing, on which the medium is applied.  For paint the support is usually canvas or a panel made from masonite or wood.  (Paper would be the equivalent support for a drawing.)

Sizing (or Size) A size is a preliminary coating often applied to the support.  It is a glue solution, several versions of which are given below.  Size is most commonly used under oil paints to prevent the colors from coming into direct contact with the canvas or board.  Such contact causes crumbing and rotting.  Acrylic colors and media, which are thinned with either water or turpentine, do not rot canvas, so no sizing is necessary.

Ground A ground is also a preliminary coating, but in this case the purpose is primarily to create a luminous undersurface for the paint.  Over a period of time colors, and especially oil colors, tend to thin, and a ground provides them with a supporting layer.  With oil paints the ground often is applied over a sizing; for acrylics it may be painted directly on the raw canvas or panel.  Ground may consist of: a white oil- or water-base paint; the traditional gesso mixture, comprised of glue, water, whiting, and titanium white powder; a ready-mixed synthetic (acrylic) gesso that eliminates the need for sizing.

SUPPORTS

Studio and Commercially Prepared Canvas

Compared to a canvas prepared in the studio, a well-prepared commercial canvas is very expensive.  The added advantage of a studio-prepared canvas is that you have a wide choice of surface qualities.  If you purchase an inexpensive commercial canvas, you may encounter the following problems:

Manufacturers label the ground on commercially prepared canvas as either oil or acrylic.  But the label does not say, for example, whether an acrylic ground canvas is first sized with acrylic resin under a coat of acrylic gesso.  If the size is lacking, surface may wrinkle during the painting process, and for years afterward.  There is one way to determine whether an oil ground is lead (flake) white or titanium white if the label does not specify.  Take an edge of the ground coat, and fold and refold.  Lead white is brittle and produces a crackle on its skin; titanium is more flexible.

Canvas with Acrylic Ground

With a commercial acrylic ground, be sure the ground is not too thin, or oil will soak through.  Hold the canvas to the light, looking for those pinholes of light that reveal an excessively thin ground.  Also check to see if the ground is applied in a consistent coat.  To prevent further absorption, add another coat of acrylic gesso, preferably with a spatula or a putty knife—instruments that will facilitate a more even coat.

Linen Canvas with Acrylic Ground

Linen by its nature takes in moisture from the atmosphere and therefore may expand in damp weather.  If the acrylic ground is not presized with acrylic medium, this fault tends to be aggravated.

Canvas with Oil Ground

On an oil-grounded, studio-prepared canvas, make sure the fabric is heavy enough to sustain the rabbitskin glue and oil priming.  Thin fabric tends to retain wrinkles.  Some pinholes of light are permissible, since they will be filled in by the glue size and the ground.  If the ground comes through to the back, your canvas is too porous.

Caution:  Do not use acrylic paints on an oil-prepared ground.  Acrylic will not adhere to oil, even though it initially seems to hold.

Support Fabrics

Linen

Texture choices in linen range from very smooth, to medium, medium rough, and finally to rough.  Experiment with each surface in order to find the one most suited to your style.  Because the best linen is closely woven, the number of threads per square inch determines the price.  In the cheapest varieties you can actually see through the fabric.  Linen not only has the widest available range of textural surfaces, but is also the most permanent and long-lasting textile.  This permanence depends on several factors—grounds, good technique, and protection from extremes of temperature.  If the canvas is stored in a humid place without occasional airing, mold will develop.  Remember, too, that linen tends to wrinkle or sag in damp weather.

Cotton

The textural range in cotton is narrow and usually does not go beyond a medium surface.  The ideal weight is Number 10.  (The number is determined by the weight of ounces per yard.)  Numbers 8 and 12, the adjacent weights, are either too heavy or too thin to stretch easily over the wooden frame.  Cotton has tow advantages over linen.  It does not absorb as much moisture and thus stays unwrinkled, even in very damp conditions.  It is also cheaper than linen.  But there is a lack of textural choice, and the manufacturing process can be undependable.  Make sure the surface is even, with no unsightly stitches, brown flecks, or threaded lumps.

Jute

Jute is beautiful, but impermanent, surface that tends to become very brittle as it ages.  Gauguin used it and his canvases have had to be relined—that is, glued to linen.  Jute is permanent only if used to make canvas to board panels.  Prepared and stretched jute canvases can be found throughout European art stores.

Panels

Masonite

Masonite is the most permanent of the rigid supports.  Untempered masonite provides a better surface and is less expensive than tempered, or oil-impregnated, masonite.  Either the rough or the smooth side of the masonite panel can be used.  Whichever one you select, apply as least one coat of your primer to the reverse side in order to prevent warping.

Hard Wood

Panels made of hard wood, although permanent, can warp if they are not cradled on the back—that is, braced with an equal stress of horizontal and vertical wood strips affixed with any white vinyl glue.

Plywood

Plywood eventually shows its grain, even if sealed, and is thus best avoided as a direct painting surface (unless your desire is to incorporate the grain into the art work).  Use it only as a support for gluing on canvas.

Plasterboard and Celotex

Plasterboard and Celotex tend to rot from within and also should be avoided.

Aluminum

Imitation canvas texture has been stamped into aluminum and impregnated with priming, but this method is at present too expensive for general use.

Paper

Provided it is all rag content and properly primed, paper is permanent.  Tape the paper to a support with brown paper tape to keep it form wrinkling as the priming dries.  For priming, use a weak glue solution— 14 or 15 parts water to 1 part glue.  Dry pigment can be added to the glue mixture to produce a toned ground.  Another possibility is two coats of acrylic gesso.
 

Making the Support

Canvas Panels         coming soon . . .

Stretching a Canvas   coming soon . . .
 

Oil Grounds for Oil Painting

In 1568 Giorgio Vasari transcribed the following recipe for preparing an oil painting for canvas:

In order to be able to convey pictures from one place to another, men have invented the convenient method of painting on canvas, which is of little weight and when rolled up is easy to transport.  Unless these canvases intended for oil painting are to remain stationary, they are not covered with gesso, which would interfere with their flexibility, because the gesso would crack if they were rolled up.  A paste, however, is made of flour and of walnut oil with two or three measures of white lead put into it, and after the canvas has been covered from one side to the other with three or four coats of smooth size this paste is spread on by means of a knife and all the holes come to be filled up by the hands of the artist.  That done, he gives it one or two more coats of soft size, and the composition of priming.  [Lives of the Painters, Sculptors and Architects, translated by Louisa Maclehose in A.P. Laurie, The Painter’s Methods and Materials, Lippincott & Co., Philadelphia, 1926.]

The preparation of oil grounds has not changed radically from Vasari’s day.  In selecting and experimenting with grounds, keep in mind some general considerations.  White is the traditional color for grounds on all supports because, as Giovanni Battista Armenini wrote in his 1587 treatise The True Precepts of Painting, dark grounds eventually darken.  Moreover, Max Doerner [The Materials of the Artist, Harcourt, Brace, and Co.] has warned that the ground exerts an extraordinary influence not only on the durability of the picture, its later preservation, and the action of colors, but as well on the painting’s luminosity.  The oil film is thinned by time, thereby exposing the ground.  For example, artists who have been observing Turner’s paintings for years insist that the pictures are becoming increasingly brilliant—no doubt because Turner worked on a pure white ground.  In de Hooch’s painting, Interior of a Dutch House, the tiles showing through the woman’s dress illustrate how time thins a paint film.

The recipes below spell out in detail the two major components of an oil ground.  The first, sizing, is a highly dilute solution of animal skin glue that is brushed on the canvas in a thin, uniform coat to prevent the oil from coming into direct contact with the cloth.  Without sizing, oil will soak into the porous fabric and cause it to become brittle and decay.  Apply the glue economically, working out the contents of each brush full, but be sure to cover the whole surface.  Do not let the glue soak through the fabric.  Be precise in measuring the amounts of water and glue, for glue sizing that is not sufficiently thinned with water makes the canvas buckle and crack.  Rabbitskin glue should be thinned with at least 10, but preferably 12 parts water to 1 part glue.  If you use gelatin (not the edible variety) for sizing, the proper proportions are 14 to 1.  Rabbitskin glue is preferred.

The oil coating is a combination of white pigment (flake white or titanium) in oil.  After the size dries, spread the oil coating on evenly with a spatula, and make sure it is thin enough to expose the texture of the canvas.  The composition of the ground should also be considered.  Although most technical experts find commercially prepared white-lead pastes adequate, remember that the oil used in these products is not a s refined as that used in the manufacture of artists’ colors.  It will yellow in a relatively short period.  The inclusion of lead in these house paints has been outlawed in the United States.  Hence, the painter must work with the superior professional lead, known as flake white.  Titanium white has been widely used as a substitute for flake.  Although it dries more slowly, it creates a less brittle surface.  But whichever white you choose, never thin it with oil in this priming coat.  A ground should be lean—that is, relatively oil free.  If thinning is necessary, dilute the white with a little turpentine or a mixture of turpentine and varnish.

Finally, a ground prepared by the artist has advantages over one on a commercially prepared canvas.  It is less absorbent.  When a thin wash of turpentine is applied, it will stay on the surface and remain transparent, reflecting the white undercoat.  And color is generally more brilliant against this ground.  Being less porous, the ground keeps the paint from sinking in.
 

Gesso Grounds 

When painters commonly used panels as supports, after sizing with glue they primed the wood surface with gesso, a white coating substance composed of chalk or whiting in a glue and water solution.  Although generally too brittle for canvas—a slight jolt will readily cause cracks—gesso can be combined with other materials for use on fabric supports.  For example, if you add about 20 percent boiled linseed oil to the gesso mix while it is being heated and stirred, the result is a half-chalk ground, which the oil renders flexible enough to apply to canvas.  Experts are divided about the permanence of this gesso-oil ground.  Synthetic emulsion gesso, usually called acrylic gesso, is also flexible enough to bend with the canvas (or paper) without cracking, and seems satisfactory, having withstood every test except time.  But no sign of deterioration has appeared in paintings with an acrylic gesso ground that are 22 years old.

Acrylic gesso can be brushed directly onto the canvas without prior sizing.  It will produce an extremely absorbent ground that transforms the normally shiny surface of oil paints into a relatively flat one.  If such absorbency is not desired, you should add to the canvas surface a thin coating of turpentine mixed with dammar varnish or another resin over the gesso.

Experts warn that the fluids with which conservators clean oil paintings—xylene, toluene, and acetone—will dissolve acrylic gesso grounds.  To avoid this, the best solution is a two-layered ground: an initial coat of acrylic gesso, and then a layer of a white lead oil, such as flake white.  In this case, the gesso’s brilliant white surface requires only a very thin oil covering, so carefully apply a small amount of the flake white with a spatula or a palette knife.

The alternative to a canvas support is a panel.  Wood panels have been employed from early Egyptian times.  Among the most popular woods since the early Renaissance are beech, cedar, fir, chestnut, poplar, mahogany, oak, and olive.  The wood must first be seasoned— that is, aged— and then expertly braced by gluing strips of wood about a half inch thick to the back of the panel.  Affix the strips in a grid pattern with a polyvinyl acetate (p.v.a.) glue, such as Elmer’s.  Avoid plywood, which usually cracks, unless you cover it with canvas.  The canvas must be soaked in glue size, wrapped onto the panel, and the whole kept under weights until dry.

Although wood panel supports have fallen out of common usage, masonite, a modern type of fiber building board made from yellow pine wood chips, is an excellent support. It comes both tempered and Untempered, but the Untempered is preferred, because it is not coated with oil.  Oil will penetrate through to the sizing and ground for panels, whether wood or masonite.  For centuries, gesso referred to a mixture of plaster of Paris and glue water.  A typical formula today calls for equal amounts (by volume) of titanium or zinc white (in powder form), whiting, and glue water. 

Paper, too, has long provided artists with a surface for oil paint.  Use only 100 percent rag paper, and coat it with a very thin rabbitskin glue solution.  Dry pigment can be mixed with the glue to produce an allover ground color.
 

Recipes for Grounds  coming soon . . .