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STITAH: Info sheet on PIGMENTS / Phoebe Dent Weil /
phoebe@northernlightstudio.com
Refractive Index or index of refraction
-ratio of velocity of light in air to velocity of light in X -measured by the angle at
which the ray of light is bent
-higher the RI the more the substance will impede the velocity of light-http://www.naturalpigments.com/education/article.asp?ArticleID=8
air
1.0008 / water 1.3300
linseed oil 1.480 but rises over time / madder lake 1.66
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REMBRANDT’S PIGMENTS with brief descriptions
Phoebe Dent Weil
E-mail: phoebe@northernlightstudio.com
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LEAD WHITE: (It. Biacca; flake white, Cremnitz white) TOXIC: Poisonous if
inhaled as dust or ingested. Basic lead carbonate [2PbCO3 . Pb (OH)2]—Made by
exposing lead to vinegar vapor and subsequently to CO2 produced by decomposing
manure or tanbark, as described in the ancient literature by Theophrastus, Pliny and
Vitruvius. It is also found in nature as the mineral cerrussite. It was manufactured
in the 17th c. by the ‘Dutch’ or ‘stack’ process. It can be used for thick impasto as it
enhances the drying of linseed oil without distortions. Lead white is highly
absorbent to X-rays. Cremnitz white is prepared by the action of carbon dioxide on
litharge (PbO), and is considered whiter, denser, and more crystalline than
ordinary Dutch-process white lead. When heated at moderate temperature it turns
bright yellow because of the formation of massicot ; higher temperatures melt the
massicot and changes it to litharge and even further heating oxides it to red lead
(minium). Pure lead white was known as schulpwit, or flake white; a cheaper
grade to which chalk was added was known as ceruse or loodwit and was used for
grounds and for underpaint layers. Rembrandt used lead white in flesh tones, white
cuffs and collars and in pastose highlights.
CHALK: (calcium carbonate, whiting) [CaCO3]--occurs naturally. Largely composed
of remains of minute sea organisms. Chalk was used in the Netherlands combined
with animal skin glue as the primary constituent of grounds for panel painting,
whereas gesso (calcium sulfate) was used in Italy. Chalk is fairly transparent when
mixed with linseed oil. Rembrandt used chalk to add body and translucency to
other pigments without changing color.
VERMILION (cinnabar, It. Cinabro): [HgS] TOXIC- poisonous if inhaled as dust
or ingested:—Mercuric sulfide—Found naturally as the mineral cinnabar which is
the principal ore of the metal mercury. Pliny referred to it as minium, which later
came to refer to red lead. It comes in various shades of red according to its method
of preparation. Vermilion is one of the heaviest pigments, having excellent body and
hiding power. It goes black after prolonged exposure to strong light. Strictly
speaking, “cinnabar” should refer to the natural product, while “vermilion” should
apply exclusively to the artificial product (heating black mercuric sulfide). Dutch
vermilion, produced by direct combination of mercury and sulfur with heat followed
by sublimation, was highly developed in the time of Rembrandt. Rembrandt
typically preferred to use a bright red ocher heightened by the addition of red lake
rather than vermilion which he used only occasionally.
P.D. Weil / Rembrandt Pigment List, ctd.
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THE LAKE PIGMENTS—transparent glazing pigments produced from textile dyes
fixed to a precipitate formed with alum and potash or to a chalk substrate. They
were typically used in oil painting to produce effects of richness and depth over
opaque underlayers, though rarely used for this purpose by Rembrandt who
typically mixes lakes directly with other pigments to enrich their color.
RED LAKES:
MADDER LAKE (It. Lacca, alizarin crimson): --derived from the name of
the insect “coccus lacca”. Madder lake is a natural dyestuff from the root of
the madder plant (rubia tinctorium)---formerly cultivated extensively in
Europe and Asia Minor. The coloring matter is extracted from the ground
root by fermentation and hydrolysis with dilute sulfuric acid. Madder lake
and rose madder for artists’ pigments are prepared from the madder extract
by adding alum and precipitating with an alkali. Synthetic manufacture
begins in 1868. Madder lake is a poor dryer in linseed oil.
CARMINE:
COCHINEAL CARMINE (grana): --natural organic dyestuff made from the
dried bodies of the female insect, coccus cacti, which lives on various cactus
plants in Mexico and in Central and South America. First brought to Europe
shortly after the discovery of those countries, about 1523. The coloring
principle of cochineal extract is carminic acid which gives a scarlet red
solution with water and alcohol and a violet solution with sodium hydroxide.
The cochineal lakes are not permanent to light. In oil, however, they are
fairly stable. Cochineal lake is a poor dryer.
KERMES CARMINE (granum, vermiculus, coccus, <krim Persian for
worm): --from a similar wingless scale insect found in different areas of
Europe and theOrient. The host plants are scarlet oak, roots of the perennial
knawel and strawberries as well as broad beans. Kermes contains only
about 1/10 the amount of coloring matter as cochineal. Carmine nacarat is a
very pure form of carmine. Lac is a colorant related to cochineal and kermes,
produced by the lac insect in India and South East Asia.
YELLOW LAKES:
BUCKTHORN (schietgeel, giallo santo, Dutch pinke, stil de grain): --made
from unripe Buckthorn berries, of which the color is extracted with potash
and fixed onto a substrate of aluminum hydrate. Yellow lake in oil is
perfectly transparent since the refractive indices of aluminum hydrate and
oil are very close to each other. Unfortunately the yellow color in schietgeel,
rhamnetin, is not lightfast, causing the yellow glaze to fade, and if over a blue
underpaint to produce green, the blueish color underneath will become
dominant. The name derives from verschietgeel which means “disappearing
yellow”. When precipitated onto a chalk substrate, the pigment was known
as a pink or pinke . Rembrandt typically used buckthorn yellow mixed with
other pigments thereby avoiding the problem of fading. Lake made from the
purplish ripe buckthorn berries produces a lake pigment known as sap
green. Buckthorn is a poor dryer.
P.D. Weil / Rembrandt Pigment List, ctd
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WELD: --natural yellow dyestuff, obtained as a liquid or as a dry extract of
the herbaceous plant, Dyer’s Rocket (Reseda luteola) formerly cultivated in
central Europe. Weld is a poor dryer.
LEAD-TIN YELLOW (massicot, It. Giallorino or giallolino): [Pb2SnO4] TOXICPoisonous if inhaled or ingested: --a lemon-yellow to slightly orange-pink
manufactured pigment, used mainly during the 15th to 17th century. It was
apparently developed in connection with ceramic glazes and opacifiers for glass.
Like lead white it is a dense and opaque pigment, dries well in linseed oil and can be
used to produce high impasto highlights.
EARTH PIGMENTS— OCHERS, SIENNAS, & UMBERS—all from naturally
occurring sources and all containing natural ferric oxide (Fe2O3)—The earth colors are
very stable in all painting media and do not interact with other more chemically sensitive
pigments. Their stability, range of color and range of translucency to opacity suited
Rembrandt’s purposes well and therefore tend to predominate in most of his paintings.
Ochers, the most opaque of the earth colors, are fairly pure hydrated (yellow) or
anhydrous ferric oxide (red), with colors ranging from yellow, orange, brown or red.
Siennas contain greater proportions of mineral impurities in addition to the ferric oxide,
especially alumina and silica that makes them more transparent. Siennas can be used raw
or roasted (burnt sienna) to produce a warmer shade. Umbers contain in addition to iron
oxide, some black manganese dioxide that has a siccative effect on linseed oil. Therefore
they are useful additions to ground layers to promote faster drying. Umbers can be used
raw, or gently heated to produce burnt umber that has a warmer tone.
CASSEL EARTH (Cologne earth, Vandyke brown)—not strictly speaking an earth
pigment but rather an organic pigment containing some inorganic minerals
originating from peat or decayed wood deposits. It is a transparent brown often
used by Rembrandt for his initial monochromatic sketching-in of a composition and
for deep brown background glazes. Cassel earth is a very poor dryer, hence
Rembrandt always mixed it with other earth pigments to avoid this defect.
BLUES:
SMALT (It. Smalto): --a blue potash glass containing cobalt oxide as coloring
ingredient, popular because of its low cost. Smalt manufacture became a specialty
of the Dutch and Flemish in the 17th century. If ground too fine, it loses its color,
therefore the particles of smalt found in paint layers are usually quite large. Smalt
discolors in oil, as the cobalt migrates out of the glass into the oil, leaving behind an
unsightly olive green color. It eventually deteriorates to a mottled gray because of
reaction of the alkali content of the smalt with the oil medium. The admixture of
lead white prevents discoloration to a degree. Smalt was used in the Delft ceramic
industry as the blue color in Delft tiles. Smalt is a very good dryer and was used by
Rembrandt for this purpose and also to give bulk to thick glazes containing lake
pigments which are poor dryers
P.D. Weil / Rembrandt Pigment List, ctd.
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.AZURITE (It. Bice): --basic copper carbonate [2CuCo3.Cu (OH)2]. It occurs in
mines of copper and silver, frequently together with malachite, and has a somewhat
greenish appearance. It is ground coarsely because fine grinding causes it to
become pale and weak in tinting strength. Traditionally it was most used in a
tempera medium because in oil it darkens and becomes muddy. Verditer, a
synthetic azurite was available in the 17th century and has been found in some of
Rembrandt’s paintings. Azurite appears more frequently in Rembrandt’s early
work. In the later pictures Rembrandt invariably used smalt for blues. Azurite is a
good dryer because it contains copper that has a siccative effect on linseed oil.
Rembrandt therefore often added azurite to pigments that were poor dryers.
BLACKS:
BONE BLACK: (and ivory black) –a deep warm black made of ivory or bone
burned in closed retorts, consisting of carbon and calcium phosphate.[C.Ca3(PO4)
2]. Usually bones from glue stock, boiled to remove fat and glue, are used. Ivory
black is considered the deepest black of all and was used extensively by Rembrandt
in the sketchy under-layers of his paintings and for the deep black of the costumes
worn by his sitters.
Bone black is a poor dryer.
CHARCOAL BLACK : (vine black) –made from the residue of dry distillation of
wood by heating the wood in closed chambers or kilns. It has a bluish tone when
mixed with lead white. Under the microscope it is easy to distinguish the plant
fibers. Rembrandt used charcoal black primarily as a gray tinting pigment in the
upper ground layer on his canvas paintings which occasionally can be visible as the
cool half tones in flesh areas.
__________________________________
OTHER HISTORIC PIGMENTS OF INTEREST
LAPIS LAZULI- -is a precious stone of a deep blue color with white veins of quartz
and golden glittering flecks of pyrite. The blue mineral is a complex sodiumaluminum-silicate containing sulfur. The blue color is due to the sulfur ion. Cennino
Cennini gives a method for purifying the mineral for use as a pigment. To obtain a
pure blue pigment, the stone is crushed and ground and then separated from the
impurities making use of the different affinity to fat and water of the various
components. Quartz and pyrite are slightly less hydrophilic than the blue
ultramarine. By mixing the powder into a paste of wax and oil and subsequently
slowly releasing it into lukewarm water, the more hydrophilic ultramarine comes
out first, quartz and pyrite stay behind. The process is very time-consuming: the
stone, to start with, is expensive, so the resulting blue pigment is very expensive
indeed. It is therefore used with great care. One way to economize on ultramarine
was to put it over a dark under-layer or over smalt. It was usually tempered with
walnut or poppy oil, neither of which yellowed as much as linseed oil, and thinned
with turpentine, or oil of spike to make a lean paint. Synthetic manufacture begins
P.D. Weil / Rembrandt Pigment List, ctd.
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around 1830. It is permanent to light and stable in fresco. Since the refractive index
of ultramarine is so low, it serves better and is far brighter in tempera than in oil. It
is discolored in an oil or a varnish film as they yellow with age producing a greenish
appearance. Ceneri d'azzurro, or "ultramarine ashes", a residue of ultramarine after
the purest particles have been extracted.
EGYPTIAN BLUE (calcium copper silicate)-the first synthetic pigment--very stableused from early dynasties in Egypt until end of Roman period
GREEN EARTH (terra verde): an earth occurring naturally near Verona, also in
Tyrolia and in Bohemia-The coloring ingredient is iron present in the minerals
glauconite and celadonite. They are compatible with all binding media, but they
have very low hiding power in oil.
LEAD-TIN-ANTIMONY YELLOW: [ternary oxide of lead, tin and antimony] TOXICunlike Naples yellow which is pure lead antimonate- This pigment, warmer hued
than lead-tin yellow, was identified as that used by Orazio Gentileschi for the yellow
dress of the Lute Player and in St. Cecilia and an Angel in the National Gallery in
Washington. It appears to be restricted in use to Italian painting and specifically to
paintings produced in Rome. (see article by Ashok Roy and Barbara H. Berrie, "A
New Lead-Based Yellow ...."
WELD: -natural yellow dyestuff, obtained as a liquid or as a dry extract of the
herbaceous plant, Dyer's Rocket (Reseda luteola) formerly cultivated in central
Europe. Buckthorn (giallo santo) was another source of yellow dye, also fugitive.
ORPIMENT (Auripigmentum): [As2S3] TOXIC.-yellow sulfide of arsenic, occurs
naturally, also made artificially. Bright yellow, sometimes almost orange color, with
a crystalline, glittering appearance. Used as a fly killer mixed with honey (Symonds
MS). Realgar, the natural orange-red sulphide of arsenic [As2S2] is closely related
chemically and associated in nature with orpiment.
INDIAN YELLOW: -a yellow organic extract formerly prepared in India from the
urine of cows that were fed on the leaves of the mango-now made synthetically.
VERDIGRIS (It. Verde Tame) (Vert de Grece): -basic copper acetate-Known in
ancient times, its preparation was described by Theophrastus and Pliny. Prepared
by exposing sheets of copper to vinegar vapor. The resulting copper acetate is
scraped off and the copper sheet placed back over the vinegar. Verdigris was used in
oil, even though there are many warnings against using it in the treatises from the
16th c. onward, as it turns dark brown. It is the most reactive and unstable of the
copper pigments.
P.D. Weil / Rembrandt Pigment List, ctd.
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COPPER RESINATE: -a transparent, amorphous green of copper salts of resin acids
formed when verdigris-basic or neutral copper acetate-reacts with a varnish. It is
made by heating and dissolving copper acetate in colophony (rosin) and Venice
turpentine resins. Balsam or other similar resins may be used as well. It produces a
transparent green glaze.
ASPHALTUM (It. Spalto) or BITUMEN also SPALTE, ASPALATHUM: "-a brownish
black, native mixture of hydrocarbons with oxygen, sulfur, and nitrogen, and often
occurs as an amorphous, solid or semi-solid liquid in regions of natural oil deposits."
(Gettens and Stout, p.94) Prepared by heating in a drying oil, bitumen tends to
absorb the oil to produce a rich, transparent brown that never completely dries, and
ultimately causes serious cracking in the paint layers. Identified by Ann Massing in a
painting by Orazio G.(see: A. Massing, "Orazio Gentileschi's Joseph and Potiphar's
Wife)
CAPUT MORTUUM is the name for stronger burnt dark purple varieties of iron
oxide.
see also: http://www.webexhibits.org/pigments/
P.D. Weil / Rembrandt Pigment List, end.