The Technique of Fresco Painting
Prepared for Roehampton Institute, Wimbleton, England Summer 1997Materials:
For the plaster(s):
Lime: Must be high in calcium.
“Quicklime” will give you the highest calcium
content, but is very dangerous to handle. In the US, we use
“high-calcium hydrated lime” (Quick lime, and
slaked lime not available.) In Europe, good slaked lime is
sold in plastic sacks and buckets. Its quality varies, and
often needs to be sifted. There should be no less the 94%
calcium, and no magnesium in the lime. Look for “type
“S” Lime, or what is sometimes
called,”miracle” lime. Avoid
“dolomitic” lime: it is 30% magnesium, and
unusable. Using dolomitic lime will result in a pitted
surface, and possibly walls that fall apart.
Sand: Three (3) grades of clean, angular
sand (or marble dust)
1. #16 - (rough) - for the first (or "scratch") coat
2. #18 - (medium) - for the "brown" coats
3. #30 - (fine) - for the intonaco (or painting) coat.
A note on Sand: It is important that the sand be river
sand, sharp and angular, and free from salt and clay. If
the sand is prewashed, it may be used “as is”,
but if it has come from a river, or a yard where it has sat
in a pile outdoors, it must be washed. Sand comes in
different colors, all of which will change your painting
base color. White marble dust will give you a very white,
sparkle finish; browner sand will tone down your finish
some. During the Renaissance, many artists used volcanic
sand, which left a slightly blue-gray surface. .
Portland Cement: Pure white. (In the US:
difficult to find, so locate a sourse as early as
possilble)
For a portable,
constructed panel:
Exterior Plywood: 1/2 inch (for under 2’ X 2”)
; 3/4 inch for larger panels
2 inch wooden strips: for the edge of the panel, to create
raised borders, and hold in the plaster
Expanded metal lath: Any metal used must be galvanized to
prevent rust. Cut to the size of the panel
Building paper: Water proof “tar Paper”.
Galvanized staples
For a simpler, ready to use panel, not larger than 12
inches by 16 inches
Gypsum “dry wall”: not larger than 12 inches by
16 inches. ( also called “wall board” and
“sheet rock”)
Plasterweld: resinous emulsion, a bonding agent, used for
bonding plaster to concrete or cement surfaces
For construction of the portable panels: tin snips for
cutting the metal lathe utility knife (razor blade) saw /
hammer / nails
Tools for
plastering:
4-1/2 x 11 in. plasterer's trowel 5-in. pointed or square
hand trowel wood float cork float a trough for mixing
plaster. a hoe, for mixing plaster large, stiff brush 3-4
inches wide hose, with spray nozzle a few 5 gallon buckets
cloth work gloves rubber work gloves a spray bottle filled
with waste
Preparation of the
Lime:
Once you have the lime you must slake it - that is, put it
into water. High Calcium lime is caustic and dangerous:
wear a dust mask or respirator, cover the eyes with work
goggles, and have no exposed skin. You will need a plastic
container with a lid, a new, (clean garbage container works
well. If your lime will sit for a long time in one place
use a large (50 gallon) plastic trash container, but
remember that the lime may have to be transported in the
future to a worksite. You may use smaller, five gallon
buckets, which are easily obtained, and transported.) In
either case, fill the bucket about 2/3 with water and sift
the lime through your fingers into it, until it
“peaks,” that is, until enough lime has been
added so that the water will dissolve no more. For a 50
gallon bucket, you will need 120 (3 1/2 sacks) pounds. For
a 5 gallon bucket, you will use about 12 pounds of dry,
hydrated Lime. Cap it, and put it aside - somewhere where
it won't freeze - for three months. When preparation time
is short, the Lime putty can be used in three weeks, but
the longer it soaks, the better. Medieval frescoes were
often made with lime slaked for many years. This lengthy
slaking is done to prevent cracking; the longer lime
slakes, the more elastic it becomes. In Europe, already
slaked lime putty can be purchased.
Plaster is applied in 5 or more coats to a combined
thickness of 3/4 to 7/8 inches (medieval frescos were often
as thick as 2 inches. This many coats are applied for 4
reasons: (1) to give strength: the longer the plaster takes
to dry, the longer it hydrates, and the harder it will be.
(2) to prevent cracking. (3) to extend the painting time of
the final coat. (4) to make the final carbonate layer that
holds the pigment stronger.
Preparation of the
portable panels:
Plywood, constructed panel: Cut the plywood to the desired
size. Staple the tar paper to the plywood panel. Nail the 2
inch X 2 inch wooden strips to the surface of the panel,
over the paper. It should make a perfect, raised
border/frame to hold the plaster. Cut the metal lathe to
fit into the framed in area of the panel & staple it
onto the wood, through the paper every 6 inches.
Wall board panel: Cut to desired size, coat with one layer
of Plasterweld, just before the 1st coat of plaster is
applied.
Plastering:
1st coat ( italian: trullisatio / english:
“scratch coat”): The 1st coat is
trowelled onto the metal lathe, (or directly onto the still
tacky Plasterweld, if you are using wall board.) This caot
is applied to the wall, if the fresco is to be executed on
the wall. It consists of:
1-1/2 parts mixture of #16 and #18 sand (or marble dust) 1
part pure white Portland Cement 1 part lime putty (slaked
lime)
The ingredients are put into a trough, and mixed by hand
with first the hoe, then mixed and beaten with the
plaster’s trowel. At L’ecole de Beaux Art, in
Paris, we “grated” the mixture 7 times: Place
the trough on the floor, standing over it, with your feet
to either side. Pile the mix in one end of the trough, and
grate the mixture, pushing it under the trowel in small
amounts, until it collects in the other end of the trough(
the end between your ankles.) The cement will cause this
mix to harden, so don't mix up any more than you can use in
a short time.
Plastering is a learned craft, and difficult to explain
without physical demonstration. The angle at which the
trowel is held is most important, too steep and you will
draw the plaster, too flat and the trowel will stick and
pull the plaster up. Use the largest trowel for most of the
plastering, the smaller will help around the edges. Plaster
must be applied in long even strokes, smoothing as you go.
Start at the bottom and work up. A firm hand is needed as
plaster should be applied with as much pressure as
possible. Each coat must be worked in all directions to
insure against cracking. All this may sound vague, but
after you have had some practice it will make sense. The
first coat should be thoroughly scratched; Use a small
piece of the metal lathe as a comb and scratch in all
direction. This should be given a few days to a week fully
cure. You may mix the plaster for the next coats at this
time;
The next 2 coats consist of:
2 parts #18 (medium) sand or marble dust 1 part lime putty.
This mixture will not set up unless exposed to air, so mix
up enough for all three coats and store in a bucket with a
little water floating on top, covered to keep out dirt and
dust.
2nd coat (Italian: “arriccio” / french:
“crepi” / english:
“browncoat”): The first coat must be
wet down before the application of the second. A plastic
squeeze bottle, or a large, stiff brush can be used. For
large work, use a hose with a spray nozzle. Stand the panel
on end and start at the top, letting the water soak down.
You want the surface wet but with no standing water. The
second coat is applied in the same manner as the first -
worked in all directions - to a thickness of about 1/8-in.,
and "floated." Floating is done by first wetting the wood
float, then placing it flat against the surface, working in
a circular motion, with light pressure, over the entire
surface. Let the float do the work. It will smooth the high
spots and make low spots evident. Work at the surface,
taking plaster from the high spots and adding it to the low
spots, until it's a smooth, flat plane. If there are holes
in the surface, after the plaster has been applied, you may
form a little ball of the mortar, and throw it into the
hole, smoothing or “floating” it with the
float. This must also sit a few days to cure.
3rd coat (italian: “arenato” / english:
“sand coat”): The second coat must be
wet down before the application of the third. The 3rd coat
is applied, worked, and floated in the same manner as the
second, and allowed to cure. The sinopia, the full-scale
drawing is applied onto this surface, drawn on over the
rough plaster of entire wall, corrected for perspective and
other errors, all in red ocher pigment and water. The
sinopia is then used for tracings of the work to be done
each day. Because painting may only continue as long as the
plaster is still wet, each "days work" (giornata) consists
of the size area the artist can paint in about an eight
hour period.
4th /5th coat (italian: “intonico” /
french: “enduit”/ english: painting
coat): The 4th and 5th coat are, essentially 1
coat put on in steps. In the trough, mix /beat /grate: 1
part #30 sand or marble dust, 1 part lime putty.
The final two coats are applied over just the area to be
painted that day. Seams between one day‘s work and
another are planned to fall along a line in e the
composition, and must be kept very simple.
The 3rd coat must be wet down before the application of the
fourth coat. The 4th coat is applied, worked, and floated
in the same manner as the third, but is applied in a thin
layer. It is actually a “skim coat” for the 5th
layer. This must be left alone after application, 15
minutes to an hour (depending on conditions) until set. The
5th and final coat is applied as thinly as possible as it
is only for smoothing the surface. Care should be taken to
keep the trowel clean so as not to deposit any large
aggregate or foreign matter into the intonaco, wipe the
trowel off in between swipes. It should not be worked too
much, smooth as you go. Use a side light to locate and
remove all streaks and low spots. No floating is done to
the intonaco, rather it is polished. In order to polish the
surface properly, it is necessary to file the 4-1/2-in. end
of your large trowel to a rounded edge. Place a portable
light to the side of the surface, aiming so that it
“rakes” across the surface. This will
illuminate and irregularities and holes which must be
filled in and finished. Once the surface is set, gently,
using a tap and draw motion, beat the surface with this
round edge. This will bring up the flat side of the angular
aggregate and draw the lime up around it. A very hard,
flat, and smooth surface may be obtained in this manner.
To test the surface for painting readiness, a brush dipped
in water may be stroked across it. If the water is directly
absorbed, the surface is ready. If it lays on top, you must
wait. When the surface is ready, the tracing of the cartoon
(see below) is laid on top, correctly lined up, and very
lightly pounced with a small cloth bag filled with brown or
red ochre pigment. This transfers the drawing onto the
finish surface with neat, dotted lines. For panels small
enough to be painted in one sitting, a full-size cartoon
will be enough, as it may be perforated for final transfer,
omitting the sinopia altogether. If you prefer, the drawing
maybe gently incised into the plaster by drawing over the
cartoon lines with a pointed, blunt tool, in which case you
dispense altogether with the perforations and pouncing. A
side “raking” light is essential for this
method; both ways of transferring are visible in most
wall-sized frescoes.
Note on the various recipes for fresco:
The various fresco recipes given may look very
different, and rather confusing to reconcile, and indeed,
they may be. However, the different approaches may be
looked at as being essentially similar in their broad
outlines. Each has a Scratch Coat: this layer, which may or
may not contain cement is, by definition, very
rough(scratched) Its purpose is twofold: it must be firmly
anchored to the underlying wall. 2. It must be rough enough
to hold the following layer. Think of the scratches as
burrs which will extend up into the next layer, anchoring
it to the scratch coat. The next layer of plaster may be
thought of as the “intermediate, or
stabilizing” layer. It may consist of 1 or several
coats, and may include both the arriciato and the arenato.
Its purpose is threefold: it holds onto the scratch coat.
It provides tooth for the final painting coat, and, by
virtue of its thickness, it is a major component in
determining how long the intonaco, or painting coat will
take to dry. The final, painting coat, or
“intonaco” is just that: the painting surface.
it may consist of 12 or a few layers, usually all put on
prior to painting.
Cartoon Drawings are done to scale ; a full-sized cartoon
is be made before the 4th/5th coat is applied. It is fully
detailed, and in color, if possible. All details are worked
out ahead of time, for 2 reasons: 1. the painting is done
only while the plaster is fresh, usually that means one day
only. 2. Fresco is essentially a transparent medium.
Everything shows through in the finished painting. It is
recommended that the beginning fresco student make a
replica of an existing fresco (Byzantine, for the icon
painter, Roman or Renaissance for the secular painter.)
This will allow the student to concentrate on the
techniques, which are new, and sometimes very difficult,
without worrying too much about drawing and painting. It is
imperative to have your cartoon and colors prepared before
the final coats of plaster are applied, because the plaster
will be drying - and time spent doing something else is
lost painting time.
Tracing An exact tracing is made of the cartoon, and
perforated with holes, using a pin or a dressmaker’s
needle-wheel. It is left in one piece, if the fresco is to
be done in one day. If the fresco is to be done in 2 or
more pieces, the tracing is cut into those pieces.
Pigments There are many fresco pallets, from various times
and places. a simple, basic palette, easily obtained:
Vine black or spinel black or ivory black titanium white
yellow ochre red ochre brown ochre raw sienna burnt sienna
puzzuoli red venetian red almagre morodo cobalt blue
cobalt-cerulean blue viridian green yellow oxide red oxide
cadmium red
Grinding the colors tools: a large rectangular piece of
plate glass: 24 X 30, or larger a 3 inch wide glass mueller
or piece of granite that is polished on the bottom, and
fits into the palm of the hand small jars, glass or
plastic, to hold the colors large, flexible palette knife
distilled water carburndum, for surfacing the glass and
mueller
Pigments must be ground in distilled water to a state of
suspension - that is, until each particle is completely
surrounded by, or suspended in, water. This takes about 20
minutes for the softer ones and up to an hour forth harder
ones. For grinding, I use a four-pound glass mueller and a
piece of glass, about 18-24 in., square. Place the mueller
over the pigment and work in a circular motion. Every so
often draw the pigment back to the center with a palette
knife and start again. Water may be added as needed;you
will find a point where the mueller just floats over the
pigment, this is the correct wetness. To test for
suspension keep a small jar of water on the side and touch
a small amount of color to the surface; if it floats, it's
ready. Care should be taken to make sure the colors are
kept clean. If they are kept wet they may be stored in jars
indefinitely for later use. If they dry out, they must be
reground. An alternative grinding method: obtain a spinning
stone tumbler, used for grinding stones to a smooth
surface. Using a jar that fits into the spinner, fill it
1/3 full with pigment, and distilled water to fill the jar
to 2/3 full. add 5 to 7 ceramic marbles (used for mixing
ceramic glazes, and obtained at a shop that sell ceramics
supplies.) Let the pigment spin overnight, remove the
ceramic balls, and let the pigment settle, which may take
some days, depending on which pigment being ground, and
pour off the extra water. The pigment can be left in the
jar, or stored in another container. Small jars are best.
They should be sterilized in boiling water. Several colors
can be ground at once, if the tumbler can accommodate the
jars.
SELECTED LIST OF WORKS CONSULTED
Cunningham, Lawrence S., and John J. Reich, Culture and
values: a survey of Western humanities, 2nd ed. New York,
Holt, Rinehart & Winston, 1990. 2 vols.; see vol. 1.
Dimitroff, Stephen Pope, Apprentice to Diego Rivera in
Detroit and fresco workshops manual, Stephen Pope
Dimitroff, 1986.
Mora, Paolo, et al, Conservation of wall paintings,
Glasgow, Butterworths, 1984.
Nodmark, Ollie: Fresco Painting American Arists Group, inc.
New York 1947
Arts Foundation of Michigan Web Page (World Wide Web) 645
Griswold St., Suite 2164 Detroit, MI 48226 Kimberly Adams,
Executive Director - afmadams@tmn.com