The pigments behind Raphael's paintings

Natural ultramarine

Look at: the pale blue sky; the Madonna's dark blue cloak

Lapis lazuli ground to a fine powder. Used in two distinct ways in this painting. In the sky, ultramarine is mixed with white and applied over a layer of azurite also mixed with white, a two-layer blue system Raphael used consistently. In the Madonna's cloak, virtually pure ultramarine is applied as a thin glaze over an azurite underlayer, with lead white added only in the lighter areas of the drapery folds. Both the ultramarine and azurite layers are medium-rich and have darkened significantly over time as a result.

Azurite

Look at: the underlayer of the sky; the underlayer of the Madonna's cloak; the dark strip at the top on which the gold inscription is written

Basic copper carbonate. Used throughout as an underlayer beneath natural ultramarine in all the major blue areas. The dark strip at the top of the panel, on which the gold inscription sits, contains azurite and has darkened with age; it was originally a brighter blue. Also present in the purplish paint of the dark roof of the canopy, mixed with red lake.

Lead white (Cremnitz)

Look at: the lighter areas of the Madonna's cloak; the pale priming layer throughout; the architectural grey setting

Basic lead carbonate. Present in the pale yellow priming layer combined with lead-tin yellow. Used in the lighter areas of the drapery folds and mixed into the grey architectural paint alongside powdered bismuth. Forms the white underpaint in the canopy layers.

Lead-tin yellow

Look at: the throne and its lighter yellow-brown areas; the pale priming layer

Fused lead-tin oxide. Present in the pale yellow priming layer alongside lead white. Used in the lighter yellow-brown areas of the throne, where in the lightest passages it appears almost pure. Also found in the underlayer of Saint John's red drapery as part of the imprimitura.

Vermilion

Look at: the underlayers of Saint John's red drapery; the orange lining of Saint Nicholas's cope

Mercuric sulfide. Used in the underpaint of Saint John the Baptist's red drapery, mixed with red lake in the mid-tones and with red lake and black in the darkest shadow underlayers. In the orange lining of Saint Nicholas's cope, vermilion is mixed directly with red lead to produce the solid opaque orange-red.

Kermes lake

Look at: the red lake glaze on the underside of the canopy roof; Saint John's red drapery

Organic red lake from kermes insects. Found in the surface glaze on the dark underside of the canopy roof. Also present in Saint John's red drapery combined with brazilwood lake and vermilion across several layers. The kermes component retained its red colour while the brazilwood deteriorated to yellow over time, shifting the appearance of some passages.

Brazilwood lake

Look at: the underlayer of the canopy roof; the underlayers of Saint John's red drapery

Organic red lake from brazilwood. Present in the underlayer of the canopy roof mixed with kermes and other pigments. Has deteriorated to a yellow colour over time. What now appears as a yellow-brown translucent layer was originally a red lake contributing to a deep purplish red. The faded brazilwood is identifiable under the microscope as translucent yellow particles within the paint layers.

Red lead (Minium)

Look at: the orange lining of Saint Nicholas's cope

Lead tetroxide. Mixed with vermilion to produce the solid opaque orange-red of the lining of Saint Nicholas's cope.

Verdigris

Look at: Saint Nicholas's dark green cope; the scalloped fringe around the canopy; the background landscape

Basic copper acetate. Used throughout the greens of this painting. In Saint Nicholas's cope, verdigris is mixed with lead-tin yellow with white and black adjusted according to the drapery modelling, and the deepest green shadows are finished with a pure verdigris glaze. The same combination appears in the fringe around the canopy and in the mid-greens of the background landscape, where some passages are particularly translucent with a high proportion of verdigris.

Orange ochre

Look at: the brown gold-embroidered borders of Saint Nicholas's cope

Earth pigment. Used in the brown paint of the gold-embroidered borders of Saint Nicholas's cope, combined with vermilion, black, white, and a little verdigris, with a final organic brown glaze on top. Also used in the earth-toned areas of the throne.

Yellow ochre

Look at: the throne and its timber-toned areas

Iron oxide earth pigment. Used in the throne alongside lead-tin yellow for the flat lighter yellow-brown passages. Earth pigments provide the warm, muted tones of the architectural woodwork throughout.

Black

Look at: the darkest shadows of Saint John's red drapery; the underlayers of the canopy

A sulphur-rich black pigment identified in the darkest shadows of Saint John's red drapery and in the underpaint of the canopy has been characterised as a form of coal. This is distinct from the bone black used in drapery modelling elsewhere. Both appear as black in the final painting but have different chemical compositions.

Calcite

Look at: the pale priming layer throughout

Calcium carbonate. Present in the ground and priming layers. Functions as an extender rather than a primary colorant.

Bismuth metal

Look at: the light grey architectural setting

Powdered metallic bismuth used as a grey pigment, one of the unexpected discoveries from technical examination of this painting. Raphael appears to have chosen it where he required a grey tone rather than a true black. Lead white is mixed with powdered bismuth to produce the grey of the architectural setting. This use of bismuth as a grey pigment was previously unrecorded in his work.

Powdered glass (colourless)

Look at: present throughout all paint layers, most abundant in red lake glazes

Colourless glass ground to a powder and mixed into the paint. Found in all of the Raphael paintings examined from this period and most abundant in the red lake glazes, but also detected in other paint layers and in the pale yellow priming. The glass appears to have been added as a siccative (a drying agent) to speed the hardening of the oil medium.

Natural ultramarine

Look at: the pure blue of the sky upper left; the most intense blue areas of Saint Catherine's cloak

Lapis lazuli pigment. The purest blue of the sky is a single layer of natural ultramarine with white applied over the priming. The more greenish-blue areas of the clouds contain azurite mixed with ultramarine. In the blue drapery passages, ultramarine is used over azurite in the same layered system seen in the Ansidei Madonna.

Azurite

Look at: the greenish-blue clouds; the underlayers of drapery; the brownish-green landscape

Basic copper carbonate. Mixed with ultramarine in the greenish-blue cloud passages. Present in small amounts in the lighter underlayers of Saint Catherine's red drapery, where a little azurite was added to shift the colour subtly toward a more purplish tone. Also used in the brownish-green landscape and the dark brown foliage of the small tree at the left edge.

Lead white (Cremnitz)

Look at: the sky; the lighter areas of the drapery; the pale priming throughout

Basic lead carbonate. Present in the priming layer and throughout the sky and drapery passages wherever lightening is needed. In the underlayers of Saint Catherine's red drapery, the amount of lead white increases in lighter areas to build the form before the final red glazes are applied.

Lead-tin yellow

Look at: Saint Catherine's wheel; the brownish-green landscape

Fused lead-tin oxide. A key component of the wheel, combined with lead white, yellow ochre, umber, vermilion, black, and a little azurite. The same pigment mixture is used for the greenish-brown landscape, varying in proportions according to tone. Also present in the pale priming and in the dark brown foliage of the tree at left.

Vermilion

Look at: Saint Catherine's wheel; the brownish-green landscape

Mercuric sulfide. Used in the single-layer paint of the wheel alongside lead-tin yellow, yellow ochre, umber, and black. The same mixture, with varying proportions, constitutes the brownish-green landscape passages. Notably, vermilion was not used in the underlayers of Saint Catherine's red drapery; that passage relies entirely on red lake.

Madder lake

Look at: the lower layers of Saint Catherine's red drapery

Organic red lake from the madder plant. Identified by HPLC analysis as the primary red lake in the underlayers of Saint Catherine's drapery, distinguished from the kermes used on top by its characteristic fluorescence under UV microscopy. In the shadow passages, only a small amount of lead white accompanies the lake in the underlayers; in lighter areas more white is present.

Kermes lake

Look at: the surface glazes of Saint Catherine's red drapery; the hatched shadow strokes along the arm

Organic red lake from kermes insects. Applied in the upper layers and final glazes of the red drapery over the madder underlayers. The band of shadow along the outer edge of Saint Catherine's arm is reinforced with hatched surface strokes of kermes lake, accentuating the volume of the drapery. Raphael consistently used kermes on top of madder in his red drapery passages.

Yellow ochre

Look at: Saint Catherine's wheel; the brownish-green landscape

Iron oxide earth pigment described as intense yellow ochre in the technical analysis. Used in the wheel and landscape mixture alongside lead-tin yellow, vermilion, umber, and black. The intense yellow ochre contributes warmth and depth to these earth-toned passages.

Umber

Look at: Saint Catherine's wheel; the brownish-green landscape and dark foliage

Manganese-rich earth pigment (manganese detected by EDX analysis). Used in the single-layer paint of the wheel and in the greenish-brown landscape alongside the other earth pigments and lead-tin yellow. Present in the dark brown foliage of the small tree at the left edge.

Red ochre

Look at: the dark brown foliage of the small tree at the left edge

Iron oxide earth pigment. Used in the dark brown foliage of the tree at the left, combined with brown ochre, azurite, and a little lead-tin yellow. No discoloured copper green glazes are present in this passage; Raphael built the dark brown from earth pigments alone in this area.

Brown ochre

Look at: the dark brown foliage of the small tree at the left edge

Earth pigment. Used alongside red ochre, azurite, and a little lead-tin yellow in the dark foliage of the tree at the left edge of the composition.

Black

Look at: Saint Catherine's wheel; the landscape shadows

Carbon black. Used in the wheel mixture and in the landscape passages to darken and grey the tones. Also present in the darker underlayers of the drapery passages.

Natural ultramarine (lapis lazuli)

Look at: the sky; the blue robe of the woman at the bottom of the composition

Lazurite from lapis lazuli, confirmed by both Raman spectroscopy and XRD analysis. Present in the sky area and in the blue robe of the figure at the lower section of the painting. Used alongside smalt rather than azurite in this later work, a different pairing from the earlier paintings. On the flesh tones of some figures, cinnabar was found mixed with lapis lazuli particles.

Smalt

Look at: the sky; the blue robe of the woman at the lower portion of the painting

Ground cobalt-blue glass. Identified by the presence of Si, Co, K and S in EDX analysis, with particles showing the typical conchoidal shape characteristic of smalt . Used together with lapis lazuli in both the sky and the blue robe passages, replacing the azurite-plus-ultramarine system of the earlier works. Lead white is also present in the blue paint layers.

Lead white (Cremnitz)

Look at: the white underpainting visible beneath paint layers; the lighter passages throughout

Basic lead carbonate. Present in the white-yellowish underpainting applied over the red-brown ground. Used throughout the lighter passages. In the purple tunic area, pure white lead underpainting was applied before the red lake glaze to achieve the purple colour. Also identified in the brown ground area alongside iron oxides.

Lead-tin yellow

Look at: the yellow areas of the painting; traces found in the purple tunic

Fused lead-tin oxide. Identified by non-invasive XRD analysis in the yellow areas rich in calcite. Also found as trace levels in the purple colour area, likely an impurity from painting tools rather than a deliberate addition. Lead-tin yellow was widely used by Renaissance artists and its presence here is consistent with Raphael's practice across all his examined works.

Cinnabar

Look at: the red draperies; the flesh tones

Mercury sulfide in its natural mineral form (cinnabar), identified by pXRD measurement of the red draperies and confirmed as the red pigment mercury sulfide (alpha-HgS). Also found on the flesh tones mixed with lapis lazuli and cerussite.

Red lake

Look at: the purple tunic of the central figures; the red drapery passages

Organic red lake on an aluminium substrate, identified by EDX showing Al, Ca, C and Pb in the purple area. Applied as a glaze over pure white lead underpainting to produce the purple tunic colour. The purple hue results from varying proportions of red lake and blue particles mixed with white fillers and black.

Yellow earth (goethite)

Look at: the yellow passages; the ground layer

Iron oxyhydroxide earth pigment, identified by Raman spectroscopy showing bands consistent with goethite and confirmed by abundant Fe in EDX elemental mapping. Present in the yellow areas of the painting mixed with white lead, carbon black, and some smalt and lapis lazuli. Also present in the red-brown ground layer beneath all the paint layers.

Carbon black

Look at: the yellow paint areas; the ground layer; the dark shadow passages

Carbon-based black. Present in the yellow areas mixed with white lead and earth pigments. Also identified in the ground layer and in the dark underpainting passages. Traces of Mn in dark areas indicate additional compounds possibly used for shadowing the purple and blue robes of some figures.

Calcite

Look at: the ground layer; the yellow areas

Calcium carbonate. Identified by Raman spectroscopy and XRD. Present in the ground layer alongside cerussite and hydrocerussite from lead white. Also found in the yellow areas rich in calcite where lead-tin yellow was identified by non-invasive XRD. Functions primarily as a ground and filler material.