Supports for Painting:
Materials and Practices
DEFINITIONS
Size: any of various gelatinous or glutinous preparations made from glue,
starch, etc. used for filling the pores of cloth, paper, etc., or as an adhesive ground
for gold leaf on books. In painting, used to seal the support's surface to protect it from
acid and make it less absorbent. A size is not a coating; it is a penetrating liquid
employed to fill pores, to isolate coatings, or to make surfaces suitable to receive
coatings; it is not intended to form a continuous, level film. A size should be very thin,
just enough to fill the fibers of the cloth: mix 1.5 oz of rabbitskin glue into a quart of
water to create a gel of applesauce consistency. Glue must be prepared by heating without
boiling in a double boiler.
"Glue size leaves little to be desired from a functional viewpoint; its incomplete
resistance to moisture is its only fault...."
Casein has been recommended for this purpose, because when dry it is much more
water-resistant than glue or gelatin; but glue is far superior because casein is too
brittle
A modern replacement for glue sizing, is CMC (sodium carboxy-methylcellulose)
which has been used for some time in the textile industry. CMC is a cellulose ether, which
is chemically compatible with cotton or linen cellulose fiber canvas, and will expand and
contract at the same rate as the cloth. CMC remains flexible and will not shed or crack as
glue size might do in certain dry conditions. Two coats may be applied with a brush in a
low viscosity grade. This product is still in the experimental stage for artistic use; so
far I have not heard favorable reports from artists who have tried it, but they may need
to adjust the viscosity of their solutions. Mayer warns that "cellulose coatings will
form continuous films even when quite dilute, and such films would present a rather
precarious bond for the old paint...These materials produce films which are totally
foreign in composition and properties to the usual painting materials; this feature may be
of greater significance than the fact that they are related in composition to the textile
fibers."
Glue: an impure protein gelatin obtained by boiling skins, hoofs, and
other animal substances in water and used as a strong adhesive.
Used as a size for painting surfaces, the best for this purpose being rabbit skin glue
(especially on a flexible ground) which is flexible and dries out with relatively little
tension.
Gluten: the tough, viscid (sticky), nitrogenous substance remaining when flour
is washed to remove the starch: Flour Paste.
Generally not recommended for painting purposes, though there are rumors that Bouguereau
used a glutenous substance in some way in preparing at least some of his canvases.
Gypsum: a very common mineral, hydrated calcium sulfate, used to make plaster of
Paris. Primer for inflexible painting surfaces such as wood panel. (used thinly by early
artists on cloth)
Gesso: gypsum or plaster of Paris (calcium sulphate) prepared with glue for use
as a surface for painting. Today chalk (as natural calcium carbonate or precipitated chalk
- an artificial whiting) is used more commonly than the gypsum that Cennini recommended.
Chalk ground was commonly used by Northern painters.
Application of chalk and glue gesso is an art in itself and application must be done
methodically and carefully to avoid defects. If gesso is improperly applied, pinholes
caused by airbubbles can occur, as well as cracking and peeling from overconcentration of
glue, too great a variation in strength of layers (esp. strong over weak), or by
atmospheric conditions when applied.
Modern Acrylic "gesso" Polymer primers have come to be used on
pre-primed canvas, stretched canvas, and canvas boards. A basic rule of oil painting is
that each succesive layer must be more flexible than the last to avoid cracking. And when
painting in oils it should be remembered that the ground itself has some degree of
flexibility, which normally limits the use of paints to those that are at least as
flexible as the priming on the canvas. Acrylic polymers on a cloth support remain more
flexible than any oil film. However, "acrylic polymer does not contain the acids
which tend to deteriorate cotton or linen fibers. Therefore, the use of a size becomes
unnecessary. The absence of glue size and the hydrophobic character of the acrylic polymer
produces a very dimensionally stable system. A departure from the rule of applying more
flexible layers of paint over less flexible ones is encountered when using an acrylic
polymer ground for oil painting.
A survey of this type of construction has shown no detrimental effects of adhesion so far.
Layers of oil paint have remained intact over acrylic polymer grounds quite well. The
expansion and contraction of the glue size/oil ground construction, due to the absorption
and release of atmospheric moisture, is avoided by the use of an acrylic polymer ground.
Therefore, the more flexible acrylic polymer layer does not affect the subsequent layers
of oil paint as it does not expand and contract as much.
The acrylic polymer ground should not be diluted with too much water as this reduces the
effectiveness of the binding resins. Polymer primers that have been diluted to an extreme
have exhibited a tendency to powder off or decompose." --Mayer
Certainly the flexibility issue is a mute point when acrylic polymer is used as a
ground on a solid substrate such as wooden panels. The greater question is whether acrylic
resins will last as long as natural drying oils.
TYPES OF SUPPORTS
INFLEXIBLE
Wood Panel.
The best wood panels for painting are well seasoned, air-dried quarter-sawn hardwoods
to avoid warping, bowing, and cupping. Wood types that have been used by artists include:
linden, willow, lime, beach, chestnut and walnut, oak, mahogany, and cedar. The best
choices of these may be oak, a classic favorite for its strength and resistance to the
damp; mahogany, which is extremely durable, has medium to good working qualities, small
moisture content, and is of medium price; and western red cedar, used a great deal
outdoors because of its reputation for withstanding weather, thus making it ideal as a
painting support. A ground made of multiple panels glued together tongue-in-groove with
grains running in opposing directions make better supports than one solid board that is
more likely to bow and warp.
Other Wooden Supports
Wood emits acidic vapors that are detrimental to subsequent paint films. The acidic
deterioration of wood products are most notable in the quick yellowing and decay of
newsprint. And framers are well aware of the acid problems associated with cardboard matts
and backing boards that necessitate the use of 100% rag PH balanced archival boards for
permanent framing since acids from matting can migrate to the artwork and destroy it.
Adhesives used in production of engineered wood products "contribute substantially to
this chemical reaction" of acidic vapor emission. Therefore, well aged wood panels
are preferred.
Protection against these wood acids can be found in the alkali nature of calcium carbonate
gesso when used as a buffing agent between the wood and painting. Acrylic Polymer primer
is also useful in this regard. Priming should be 1/16" or more for proper protection.
Plywood: a central wooden core sandwiched between a number of thin layers of
wood which are glued together.
Blockwood: narrow parallel softwood or, less commonly, hardwood strips glued edge
to edge and faced, like ply, with a thin veneer. Comes in 3-ply and 5-ply.
Chipboard: made of chips of wood compressed into rigid panels with synthetic resin
glues. Flooring grades compressed to a density of 720 may be used for artists' supports.
Hardboard: a composite panel made by hot pressing steam-exploded wood fibers with
some resin, and relies mainly on the lignin that is naturally present in the wood to
cement the particles together. The homogenous structure of the board is said to be more
stable than solid wood, plywood or blockboard regarding warp. However, some conservators
have condemed hardboard due to outgassing and chipping and peeling from the corners. While
the marketplace promotes it as a permanent support, conservators have described it as an
"excessively self-destructive support at best."
Medium-density Fiberboards: made the same way as hardboard but with the addition of
a synthetic resin. They are considered among the most stable boards available and
"acceptably permanent." They have a less hard and glossy face side than standard
dense hardboard. The "A" grade should be used for artists' supports.
FLEXIBLE
Cloth Supports - stretched over frame or panel
The cloth is the weakest point in the survival of a well-made picture; but advantages
of weight, transportability, and the fact that defective paintings on canvas can be
repaired or conserved more satisfactorily than those on other supports, have caused linen
to retain its position as first choice as a support material ever since it came into
general use. The best cloth canvas should be closely woven and of equal thread count in
its warp and woof. Single oil primed linen may last longer than double primed because it
is more pliable and limber, more supple and less liable to crack when handled than those
with thicker coatings. For this reason, large works should be single primed. Smaller works
that demand finer paint handling, such as portraits and still life, can be double primed.
Linen Canvas: made from the fibers of the flax plant (Linum usitatissimum) it is
a long (24 to 36 inch), strong fiber that creates a more uniform texture than cotton.
Russia is the major producer of flax, but the best quality comes from a "200
kilometer wide band of country stretching from lower Normandy through Picardy to Flanders
and up into Holland, where there is a great flax-growing tradition." The best
finished linen is said to be that made in Belgium.
Cotton Canvas: the seed hair fibers of the cotton plant (Gossypium hirsutum
and Gossypium barbadense) are not as long as the linen fibers. The longest cotton
fibers are from Sea Island cotton in the United States which has staples of between one
and a half and two inches, while average cotton stables run one to one and one eighth
inches. These fibers must be spun together to make long threads which increases
irregularities and is feared by many to create a weaker strand. It does appear, however,
that a good quality loomstate cotton duck canvas of between 12 and 15 oz. is as durable as
the more commonly used lighter weight linen and may degrade more slowly in this heavier
weight. Light weight (below 12 oz.) should not be used for permanent painting.
Polyester Canvas: a synthetic fiber that creates a tight, dimensionally stable,
stiff cloth. It is believed to be more durable than linen or cotton, with a strong
resistance to acid attack. It absorbs very little moisture and has exceptionally good
dimensional stability, with good elastic recovery. While flexible, it is less likely to
stretch out of shape than the natural fibers, placing less strain on the paint layers. It
does have a very smooth surface texture, which may not be as good for thickly worked
paintings and should be stretched two way before stapling to the support using more
staples placed closer together.
Jute: while it is offered for sale, it becomes brittle and is not recommended for
permanent painting.
Hemp: A tall, annual, moracious herb, Cannabis sativa, native to Asia, but
cultivated in many parts of the world. It produces a tough fiber used for making rope,
coarse fabric, etc. Coarse hemp canvas is believed by some researchers to have been the
predomenant canvas used by the French prior to the end of the eighteenth century.
Animal Skins
Leather: tanned hide. A non-dyed, non-surface-coated leather should be used for
painting supports in order for the paint film to adhere. Stretched over wood panel.
Parchment and Vellum: calf-skin, dehaired, stretched, and scraped, then prepared
with chalk and pumice stone. also stretched over wood support.
Paper
Paper is unsuitable as a ground for professional / archival oil painting for many
reasons, including the fact that it becomes brittle and weak, is overflexible, and is
susceptible to mold, rot, and decay. Works on paper are very fragile and must undergo
extreme restorative and conservative treatments, usually within 35 years, even when
painted on 100% rag paper mounted to wood panel.
Paper can be used for quick sketches where permanence is not important.
FLEMISH PRACTICES
Painting on Wood Panel
White poplar or oak was used to create the support. To prevent the splitting of the
joined planks, one should allow for expansion and contraction without warping. To do this,
join your planks with the grain in parallel direction. On the back create several grooves
perpendicular to the grain into which you should place cross beams tongued to fit the
groove. Do not nail or glue them, but allow for the expansion of the boards to move along
the grooves and hold all in place by a loose fitting frame.
Michelle Scalera, Conservator at the Ringling Museum in Sarasota, Florida, told me how
early painters would get their wood from the black forest, then age the wood planks
through hydration and dehydration before assembling their painting support.
On the back of your panel, protect it from worms and moisture induced warp in the
following manner. Coat the back with gesso, size, tow, and a coat of black oil paint. but
don't make it too firm so that it may expand and contract with the wood. A work found
treated in this manner is still in perfect condition, showing no signs of worm or rot. (on
canvas some have recommended that the back be tanned to preserve it and keep out moisture.
However, it has been found that affixing a backing board to the frame protects the canvas
better. This is the common method used today.)
Size the front of the panel with 2-3 coats of animal skin glue or cheese powder and
quicklime. Over this spread 8+ layers of gesso. Apply the first layer thickly on a panel
not overly smooth. Then apply at least 7 more thinly. After applying each layer, allow it
to dry, sand it, and then apply the next coat perpendicular to the last. This created the
bright white ground used by the Flemish in their thin transparent method of painting. The
effect was based upon stained glass, where light would pass through the colored resinous
layers, reflect off of the bright white ground and reflect back to the viewer. However in
Italy, where they were more likely to paint in a grisaille, or dead color in black and
white, and then overglaze their color upon it, Vasari recommends 5 coats of size, applied
by sponge, and one of priming. While Palomino used only 1 coat of size followed by 1 or 2
of oil priming.
(It is warned that a board so prepared is susceptible to moisture separating the gesso
from the board, especially when using the more porous white poplar, as opposed to harder
oak or chestnut wood.)
A drawing was then traced to the white gesso ground. Afterwards, it was outlined with
brown ink and shaded in full value and much detail. After which it was over primed with a
translucent flesh toned oleo-resinous medium through which the drawing could be seen and
the white ground was still effective. Usually the drawing was coated with size before the
oil prime to keep the oil from absorbing into the gesso ground. This was done to keep the
ground pure white. (Obviously this is not necessary when painting on a tinted ground.)
Then the colors were applied thinly, at once or in layers.
The process is then as follows:
Wood panel - (Support) not overly smooth on the surface.
Size - 2 to 3 layers. Helps to protect the ground from off gassing produced by the
wood as it ages.
Ground - a thick, coarse layer of either gesso (gypsum=calcium sulphate usually
used in Southern Europe) or chalk (calcium carbonate usually used in Northern Europe and
tinted with pigment, either white or colored) bound with animal glue. Top coat with up to
7 fine layers of the same gesso or chalk applied thinly and perpendicular to each other.
Sand between coats until smooth.
(chalk bound with oil is transparent due to the similar refractive indices. This mixture
can be used to allow the surface color of the support to show through but should be top
coated with oil based layers only.)
Drawing - transfer onto ground from cartoon (preparatory drawing) or draw directly
onto ground with brush.
Ink or paint the drawing in monochrome tempera paint, distinguishing the major
values and forms.
Size again - 1 to 5 weak coats to make impermeable to oil - keeps the ground white
to reflect color through transparent oils. Also prevents dry gesso from leaching oil out
of paint film, causing it to dry out and flake off. (modern writers warn against making
the ground completely nonabsorbent as this prevents adhesion of the paint film. A light
coating of size is preferrable to reduce the surface to a semi-absorbent state.)
Imprimatura - after size is completely dry, apply an oil or oleo-resinous medium
tinted flesh tone, light brown, or warm gray. This translucent tone creates a uniform tone
over the entire image. Some artists placed this directly over the drawing, using it to
seal the gesso or chalk ground in place of the size.
Dead Color - paint the scene or image, defining the forms, values and basic colors.
Carnation - add warmer tones to flesh and final glazes and scumbles to scene to
perfect color.
Detailing - accentuate highlights and shadows.
Varnish - addition of resinous or oleo-resinous layer to protect the paint from
dirt and abrasion. Also to oil out the colors that have sunken in and create an even
sheen.
Final Advice
"The leading methods which have been described differ in many respects from those
of the Italian, and in some, from those of the later Flemish masters. Painters of all
schools have, indeed, recognized the principle that colours derive brilliancy from light
within them; but it was soon found that this object could be attained by various means. it
matters not, for example, whether the internal brightness reside in the light ground, or
whether it be reproduced at any stage of the work. A preparation of the latter
description, answering the same end as the white panel, may consist in a light but very
solid painting, by means of which the composition may be defined; and, when such a
preparation is thickly painted, the colour of the ground underneath it is obviously
unimportant. This conviction may have led to the introduction of dusky grounds; but the
indispensable condition of a solid and lighter covering upon such a priming was gradually
overlooked: some later Italian pictures exhibit the thin painting of the older Flemish
masters on grounds requiring a contrary treatment, and premature decay has been uniformly
the consequence. The opposite precaution, though apparently needless, is to be
recommended; viz. that of employing a light ground, even when the picture is intended to
be solidly painted. This was often Rembrandt's practice: it indicates his having reckoned
on the possibility, at least, of leaving his ground; accordingly it is sometimes apparent
even in those of his pictures which are (partially) loaded with colour.
It is evident that if cloth be employed instead of wood, and if the ground or preparation
be thin, the colours constituting the picture or its substratum require to be applied in
considerable body, in order to exclude air or damp from the back. The bad consequences of
a neglect of this have been already noticed. There is thus a plain reason for solid
painting on cloth, which is not applicable to panels; and, as the Venetian oil painters
happened to prefer cloth from the first, their whole process was soon influenced by this
circumstance, and differed widely in its means, though not in its end, from that of the
Flemish masters.
When Rubens remarked that wood was preferable for small pictures, he may, therefore, have
meant that the solidity which is indispensable for works executed on cloth may be too
apparent, since small pictures can only be seen near. This and other principles of the
kind, founded on a not unreasonable attention to the impressions of the ordinary
spectator, were, however, set at nought by those who, like Rembrandt, considered art as an
acknowledged convention, and who thought it at least unnecessary to conceal its means. It
is also to be remembered, that, if a certain smoothness of surface be desired at last, the
substance required may be furnished by a sufficiently thick ground (such as Armenini
describes); the solidity of the picture, properly so called, is then not so
essential."
This advice is challenged by Michelle Scalera, Conservator at the Ringling Museum,
which houses a number of large works on canvas by Rubens, who painted thin, transparent
shadows, building up mass only in the lights. These works from the mid 1600s have
withstood the test of time on their original linen supports.
The greater issue may be the value of the ground color. Darker grounds will eventually
show through thin areas of lighter paint, creating pentimento. Thus, thinly painted images
should be done on light grounds. Where a dark ground is used, the midtones and highlights
must be built up in greater mass, and in multiple layers.
Painting on Cloth
Throughout the 15th and 16th centuries, and even into the 17th c. in areas of Northern
Europe, cloth was considered only for decorative arts such as banners or wall hangings.
Patrons preferred their larger and more prestigious commissions to be executed on more
durable solid supports - wood panels. "Painted hangings were considered second-rate,
even if they were created by well-known artists." (Nico Van Hout) Canvas or linen was
therefore used primarily for preliminary studies and for full scale cartoons for
embroidered tapestries. Such is the case with the large canvases by Rubens in the Ringling
Museum in Sarasota, FL. But in Italy, especially Venice, canvas was used for high art
because it could be rolled up and shipped easily. Cloth's light weight also made it
appealing and it eventually won out in the North as well.
The preparation of canvas for painting during this period is somewhat odd, and contrary
to acceptable practices today, as inflexible gesso was sometimes ground into the cloth.
However, this may be the "cheaper form of lead white extended with chalk, known in
the seventeenth century as lootwit, as opposed to pure lead white known as schelp-,
schilp-, or schulpwit." (see warnings against chalk on cloth below) Abraham
Latombe, an Amsterdam painter of the 17th century, "considered a single layer of lead
white and umber sufficient, (but) he states that two layers will make a canvas more
'unified.'" "Painters knew that the hygroscopic and rather brittle nature of a
chalk in glue ground made it unsuitable for use on canvas, especially when thickly applied
and to large scale canvases which might be rolled up for transport," according to
Hendriks. She claims that "lead white in oil-based primings, mixed with other
pigments (were) usually applied to canvas." Chalk in glue grounds seem to have been
an occasional application to cloth and an oddity of the 1600s that may have been
determined by cost.
The process for preparing cloth for painting is described by Nico Van Hout. Meaning
and Development of the Ground Layer in Seventeenth Century Painting -
Additional comments from Ella Hendriks. Johannes Cornelisz. Verspronck. the
Technique of a Seventeenth Century Haarlem Portraitist. Both from the book Looking
Through Paintings: The Study of Painting Techniques and Materials in Support of Art
Historical Research , 1998
- ISBN 90 6801 575 3 and 1 873132 56 5.
Linen Canvas - (Support) freed of slubs and smoothed with a pumice stone.
Size - Vasari recommends 3 to 4 layers of weak glue applied with a knife to fill
the pores of the cloth. Then add 1 or 2 more layers of glue. Armenini's recipe calls for
filling the weave with flour, oil and one third fine lead white using a knife, bone, or
piece of wood. then coat with 2 or 3 layers of soft glue. (flour is discouraged by
Volpato, however, stating that if it is too stiff it will crack and the paint will scale
off. But if it is too weak the damp causes the canvas to decay, and the mice eat it.)
Others soaked the cloth in glue before laying it out and rubbing it. The goal was to
create a smooth surface that would reduce the quantity of chalk to be used for a ground,
thereby decreasing the thickness and increasing the flexibility of the whole.
Ground - Chalk or gesso was applied over the size. The difficulty was with a thick
layer: "because the ground was less flexible than the support, paint began to flake
off, after the canvases had been rolled up." For this reason "Cennini had
already indicated that only the interstices between the threads should be filled with
gesso (thus banners and hangings could survive continuous movement far better.)"
Again Volpato warns that the key is in the glue. A strong glue "spoils the
canvas" and "only a very little gesso is required." But despite these
warnings, "canvases with thick grounds were still regularly employed in the North,
even by the likes of Rubens and Hals."
Imprimatura - Grounds were tinted by adding paint, palette scrapings, or brush
washings. Others added an imprimatura (isolating layer) of pigment in oil. Some times
Veronese omitted his brownish or flesh-colored imprimatura and painted directly on top of
the gesso. Tintorreto usually used a thin gesso layer with a black or brown imprimatura,
composed of ochre, charcoal and palette scrapings in oil. But he occassionally omitted the
gesso ground and painted with oil paint directly on the sized linen. (It is customary
today to prime the sized canvas with a layer of oil paint) Rubens experimented with
red-brown gesso primed canvases in Italy, but used grey imprimatura layers over a white or
earth colored ground layer when he returned home. (this can be described as a double
ground) "The neutral grey tone could function as the mid point in tonal values and
could be used to create halftones, shadows or backgrounds."
Drawing - Transferred from a cartoon or drawn on with black or red chalk or painted
directly with a brush in oil. Values may be layed in in oil.
Dead Color - paint the scene or image, defining the forms, values and basic colors.
Carnation - add warmer tones to flesh and final glazes and scumbles to scene to
perfect color.
Detailing - accentuate highlights and shadows.
Varnish - addition of resinous or oleo-resinous layer to protect the paint from
dirt and abrasion. Also to oil out the colors that have sunken in and create an even
sheen.
The more traditional and modern method would be:
Cloth Support
Size one or two thin coats brushed on.
Lead in oil Priming (today often substituted with less toxic and more opaque Titanium
oil priming or acrylic polymer priming)
An Imprimatura may be added either as a stain or as a double ground, but is
unnecessary as a true isolating layer.
Continue with Drawing and Painting.
Just as today, artists worked in different methods based upon their genius and their
personality. Some, like Frans Hals, did not bother with preliminary drawings, but chose to
work in a more direct manner, as noted by Van Mander:
These fellow-artists go to it, without great pains, working direct with brush and paint
with a free approach and thus set down their paintings deftly in the dead-colour; they
're-dead-colour' too sometimes, soon after, so as to achieve a better composition. Thus
those who are abundantly inventive go audaciously to work, thereafter making an
improvement here and there."
We should learn from this that there is no one right way to paint.
Provided that we apply the technical knowledge of our craft to create lasting pictures, we
are free to design our paintings as we see fit.
History, Definitions, and Techniques | Drying Oils and Mediums
Resins and Varnishes | Pigments
Past |Pigment Chemistry
Supports for Painting | Grounds on Canvas
| Techniques of Past Masters
Discussion with National Gallery Conservator
Info from: SANDERS-STUDIOS.COM
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