Craquelure

Last updated October 25, 2024

Craquelure (French : craquelure; Italian : crettatura) is a fine pattern of dense cracking formed on the surface of materials. It can be a result of drying, shock, aging, intentional patterning, or a combination of all four. The term is most often used to refer to tempera or oil paintings, but it can also develop in old ivory carvings or painted miniatures on an ivory backing. Recently, analysis of craquelure has been proposed as a way to authenticate art.

In painted surfaces

Painting systems are composed of complex layers with unique mechanical properties that depend on the type of drying oil or paint medium used and the presence of paint additives, such as organic solvents, surfactants, and plasticizers. Understanding the mechanism of craquelure formation in paint and the resulting crack morphology provides information about the methods and materials used by the artists.

Characterization of craquelure morphology

There are seven key features used to describe craquelure morphology:^[1]

Local and global direction of cracks
Relationship to weave or grain direction of support
Crack shape
Crack spacing
Crack thickness
Termination of cracks
Organization of crack network

These seven criteria have been used to identify "styles" of craquelure, which relate crack patterns to various historic schools of art. This links the crack patterns with specific time periods, locations, and painting styles.

Italian paintings on panel (1300–1500): cracks oriented perpendicular to wood grain with jagged lines and distinct secondary networks of thin cracks^[1]
Flemish paintings on panel (1400–1600): cracks oriented parallel to wood grain with smooth, straight segments; uniform thicknesses and small, square islands observed^[1]
Dutch paintings on canvas (1600s): cracks oriented perpendicular to major axis of painting with jagged lines and square junctions; cracks tend to follow weft and warp of canvas support^[1]
French paintings on canvas (1700s): non-directional cracks with smooth, curved lines in random distributions; newly-developed, stiffer sublayers tended to delocalize tension from the support and remove the connection between crack direction and canvas weave^[1]

Distinguishing Italian and French paintings by craquelures

Paintings do not have flat surfaces but rather an uneven texture because of the wood, animal glue, ground or gesso, paint, binder used, etc. Since the elements used to create paintings vary by region, surface textures can also vary according to where they were produced. Italian painters usually used a thin ground surface, which led to their work developing skinny, thin cracks, while French painters have swirling cracks because of a much thicker ground surface.

Craquelure during drying

During drying, the pictorial layer tends to shrink as volatile solvents evaporate. Non-uniform shrinkage across the painting surface is caused by differential adhesion to the sublayer by different paint species and leads to large tensile stresses in the top paint layer. Crack formation during drying depends strongly on adhesion to the sublayer, paint film thickness, composition, and the mechanical properties of the sublayer.^[2] Craquelure formed during the drying process appears within days of painting and is characterized by shallow cracks that are localized to the topmost layers of paint. This localization results from capillary forces, which constrain drying stresses to the free surface of the painting.^[2] Drying cracks are usually isotropic due to the fine dispersion of pigment particles within the evaporating volatile solvents.^[2]

Crack propagation at a critical strain, $\epsilon _{m}$ , is opposed by an unfavorable increase in surface energy as the crack elongates and promoted by a release in the elastic energy of the material near the crack. The condition for the propagation of a drying crack can be evaluated precisely using fracture mechanics.

Adhesion to sublayer

Crack width is heavily dependent on the ability of the top paint layer to adhere to the sublayer. If poor adhesion between these layers occurs, the pictorial layer can slide over the sublayer and create dramatic, wide cracks in response to uneven tensile strains during solvent evaporation.^[2] Unlike aging cracks, the width of drying cracks is highly varying as a result. Poor adhesion can occur if the painter mixes too much oil or other fatty substance into the sublayer material.

Film thickness

Below a critical film thickness, $h_{c}$ , the pictorial layer will remain crack-free. Cracks are not able to propagate in thin films because the decrease in elastic energy as the crack elongates is not enough to negate the concurrent increase in surface energy. The critical film thickness is approximated by:

$h_{c}={\frac {E_{p}\Gamma }{Z\sigma ^{2}}}$

where $E_{p}$ is the elastic modulus of the pictorial layer, $\Gamma$ the surface energy of this layer, Z a dimensionless constant that depends on the cracking pattern, and $\sigma$ the stress experienced during drying.^[2]

Films thicker than this critical value display networks of cracks. The degree of connectivity between nucleation sites increases with film thickness, so that thicknesses near the critical value are characterized by isolated star-shaped crack junctions and thick films show more complete networks.^[2]

Sublayer properties

The spacing of cracks during drying depends strongly on the stiffness of the support, or sublayer. An infinitely stiff sublayer does not contribute to the strain in the pictorial layer, so that $\epsilon _{p}=\epsilon _{m}$ , where $\epsilon _{p}$ is the stiffness of the pictorial layer. The crack spacing for an infinitely stiff support is approximated by:

$d\approx {\frac {4h\Gamma }{E_{p}a\epsilon _{m}^{2}}}$

where $h$ is the thickness of the pictorial layer, $\Gamma$ the surface energy of the pictorial layer, $E_{p}$ the elastic modulus of the pictorial layer, and $a$ the depth of the crack.^[2]

For a less stiff sublayer, an additional strain in the sublayer, $\epsilon _{s}$ , lessens the strain in the pictorial layer such that $\epsilon _{m}-\epsilon _{s}=\epsilon _{p}$ . If the ratio of the strains between the two layers is approximately the same as the ratio of their elastic moduli, the crack spacing for a support with finite stiffness can be approximated as:

$d\approx {\frac {4h\Gamma }{E_{p}a\epsilon _{p}^{2}(1+E_{p}/E_{s})^{2}}}$

where $E_{s}$ is the elastic modulus of the sublayer.^[2] The denominator in this approximation indicates that crack spacing is dependent on the mismatch in the elastic moduli of the two layers; therefore, regions with stiffer paints tend to have cracks that are more spread out.

Other effects

Changes in the relative humidity during the drying process affect both the ground layer and support of a painting, promoting crack propagation. Paintings involving hygroscopic materials like wood supports or gesso ground layers are especially susceptible to variations in relative humidity. Gesso is brittle at relative humidities (RH) below 75%; as RH increases, gesso becomes less stiff and transitions to a ductile state.^[3] Variations in RH cause highly non-uniform tensile strains across the gesso surface, and when the material contracts upon drying, it fractures.^[4] Craquelure formed during gesso drying are particularly noticeable.

Similarly, wood supports respond significantly to changes in RH. Wood grains tend to swell perpendicular to the grain axis when they are exposed to moisture.^[5] As a wet ground layer is applied to the surface of a wood support, the wood in contact with the layer swells while the back of the panel remains unchanged. This can contribute to cupping, in which the panel of wood starts to bow transverse to the wood grain. The increased strains on the convex side of the cupped wood panel causes further fracture in the ground layer as it dries.^[5]

Craquelure during aging

Compared to their drying counterparts, aging cracks are sharper, deeper, and are developed over the lifetime of the painting.^[2] This type of craquelure is much more difficult to predict and model because it depends on the specific environmental changes and chemical aging reactions the paint is subjected to. Critical processes that contribute to aging craquelure include direct impacts, gradients in temperature and relative humidity, support deformation, restoration processes like canvas reinforcement and stretching, and oxidation reactions that make the surface chalky or more brittle. In general, the pictorial layer becomes more brittle as it ages, which makes it unable to accommodate the stresses induced by environmental factors.^[2]

Induced craquelure

Induced craquelure can be created by a variety of techniques, and in paintings is often used by forgers of Old Master paintings, which would normally show some. Art forger Eric Hebborn developed a technique and Tony Tetro discovered a way to use formaldehyde and a special baking process.^[6] Craquelure is almost impossible to accurately reproduce artificially in a particular pattern, although there are some methods such as baking or finishing of a painting by which this is attempted. These methods, however, generally achieve cracks that are uniform in appearance, while genuine craquelure has cracks with irregular patterns.^[7]

Craquelure is frequently induced by using zinc white paints as the underlayer in pentimento techniques. Zinc whites with small zinc oxide particles (~250 nm) are more successful at inducing craquelure than larger particles because it does not adhere to the sublayer.^[8] Additionally, zinc white paints using linoleic acid-based binders are more successful at producing craquelure than paints with other binders.^[8]

In ceramics

Craquelure affecting the glaze in ceramics may develop with age but has also been used as a deliberate decorative effect, which has a long history in Korean and Chinese pottery in particular.^[9] These deliberate glazing effects are usually known as "crackle", with crackle[d] glaze or "crackle porcelain" being common terms. It is typically distinguished from crazing, which is accidental craquelure arising as a glaze defect, although in some cases, experts have difficulty in deciding whether milder effects are deliberate or not.^[10] Some may also only have developed with age. Leading Chinese wares of the Song and Yuan dynasties with deliberate crackle glazes are Guan ware and Ge ware; in Ru ware, the milder crackle may be accidental, though the majority of pieces have it.

Ge ware can have a type of double crackle, known as "gold thread and iron wire", where there are two patterns, one with wide and large crackle and the other with a finer network. Each set of cracks has had the effect heightened by applying a coloured stain, in different colours.^[11] There are multiple layers of glaze, and the wider crackle develops first, with the finer one developing inside those sections. The crackle may take some time to appear after firing and is probably mainly caused by rapid cooling^[12] and perhaps low silica in the glaze.

Modern applications

Acrylic craquelure

The modern decor industry has used the technique of craquelure to create various objects and materials such as glass, ceramics, iron. This was made possible by the use of marketing kits that react with the colors used in decorative acrylic colors. The extent of craquelure produced varies according to the percentage of reagent and time of use. To highlight the cracks, glitter powder—usually available in copper, bronze and gold—is used. Mixing different brands of ready-made products to mimic craquelure results in various sizes and patterns of cracks.^[7] Software programs are available for creating craquelure in digital photos.^[13]

Use in art authentication

Methods that utilize craquelure as a means of detecting art forgery have been proposed. Historical craquelure patterns are difficult to reproduce and are therefore a useful tool in authenticating art. Modern detection techniques rely on feature extraction at crack junctions and image matching to verify the authenticity of artwork with high accuracy.^[14]

Related Research Articles

Acrylic paint is a fast-drying paint made of pigment suspended in acrylic polymer emulsion and plasticizers, silicone oils, defoamers, stabilizers, or metal soaps. Most acrylic paints are water-based, but become water-resistant when dry. Depending on how much the paint is diluted with water, or modified with acrylic gels, mediums, or pastes, the finished acrylic painting can resemble a watercolor, a gouache, or an oil painting, or it may have its own unique characteristics not attainable with other media.

Oil painting is a painting method involving the procedure of painting with pigments with a medium of drying oil as the binder. It has been the most common technique for artistic painting on canvas, wood panel or copper for several centuries, spreading from Europe to the rest of the world. The advantages of oil for painting images include "greater flexibility, richer and denser color, the use of layers, and a wider range from light to dark". But the process is slower, especially when one layer of paint needs to be allowed to dry before another is applied.

Gesso, also known as "glue gesso" or "Italian gesso", is a white paint mixture used to coat rigid surfaces such as wooden painting panels or masonite as a permanent absorbent primer substrate for painting. It consists of a binder mixed with chalk, gypsum, pigment, or any combination of these.

Canvas is an extremely durable plain-woven fabric used for making sails, tents, marquees, backpacks, shelters, as a support for oil painting and for other items for which sturdiness is required, as well as in such fashion objects as handbags, electronic device cases, and shoes. It is popularly used by artists as a painting surface, typically stretched across a wooden frame.

A composite material is a material which is produced from two or more constituent materials. These constituent materials have notably dissimilar chemical or physical properties and are merged to create a material with properties unlike the individual elements. Within the finished structure, the individual elements remain separate and distinct, distinguishing composites from mixtures and solid solutions. Composite materials with more than one distinct layer are called composite laminates.

<span class="mw-page-title-main">Compressive strength</span> Capacity of a material or structure to withstand loads tending to reduce size

In mechanics, compressive strength is the capacity of a material or structure to withstand loads tending to reduce size (compression). It is opposed to tensile strength which withstands loads tending to elongate, resisting tension. In the study of strength of materials, compressive strength, tensile strength, and shear strength can be analyzed independently.

A thin film is a layer of materials ranging from fractions of a nanometer (monolayer) to several micrometers in thickness. The controlled synthesis of materials as thin films is a fundamental step in many applications. A familiar example is the household mirror, which typically has a thin metal coating on the back of a sheet of glass to form a reflective interface. The process of silvering was once commonly used to produce mirrors, while more recently the metal layer is deposited using techniques such as sputtering. Advances in thin film deposition techniques during the 20th century have enabled a wide range of technological breakthroughs in areas such as magnetic recording media, electronic semiconductor devices, integrated passive devices, light-emitting diodes, optical coatings, hard coatings on cutting tools, and for both energy generation and storage. It is also being applied to pharmaceuticals, via thin-film drug delivery. A stack of thin films is called a multilayer.

<span class="mw-page-title-main">Dendrite (crystal)</span> Crystal that develops with a typical multi-branching form

A crystal dendrite is a crystal that develops with a typical multi-branching form, resembling a fractal. The name comes from the Ancient Greek word δένδρον (déndron), which means "tree", since the crystal's structure resembles that of a tree. These crystals can be synthesised by using a supercooled pure liquid, however they are also quite common in nature. The most common crystals in nature exhibit dendritic growth are snowflakes and frost on windows, but many minerals and metals can also be found in dendritic structures.

Seismic anisotropy is the directional dependence of the velocity of seismic waves in a medium (rock) within the Earth.

Nanoindentation, also called instrumented indentation testing, is a variety of indentation hardness tests applied to small volumes. Indentation is perhaps the most commonly applied means of testing the mechanical properties of materials. The nanoindentation technique was developed in the mid-1970s to measure the hardness of small volumes of material.

Aging is a process by which an artwork, typically a painting or sculpture, is made to appear old. It is meant to emulate the natural deterioration that can occur over many decades or centuries. Although there may be "innocent" reasons for it, ageing is a technique very often used in art forgery.

In mechanics and materials science, strain rate is the time derivative of strain of a material. Strain rate has dimension of inverse time and SI units of inverse second, s⁻¹.

Stranski–Krastanov growth is one of the three primary modes by which thin films grow epitaxially at a crystal surface or interface. Also known as 'layer-plus-island growth', the SK mode follows a two step process: initially, complete films of adsorbates, up to several monolayers thick, grow in a layer-by-layer fashion on a crystal substrate. Beyond a critical layer thickness, which depends on strain and the chemical potential of the deposited film, growth continues through the nucleation and coalescence of adsorbate 'islands'. This growth mechanism was first noted by Ivan Stranski and Lyubomir Krastanov in 1938. It wasn't until 1958 however, in a seminal work by Ernst Bauer published in Zeitschrift für Kristallographie, that the SK, Volmer–Weber, and Frank–van der Merwe mechanisms were systematically classified as the primary thin-film growth processes. Since then, SK growth has been the subject of intense investigation, not only to better understand the complex thermodynamics and kinetics at the core of thin-film formation, but also as a route to fabricating novel nanostructures for application in the microelectronics industry.

Material failure theory is an interdisciplinary field of materials science and solid mechanics which attempts to predict the conditions under which solid materials fail under the action of external loads. The failure of a material is usually classified into brittle failure (fracture) or ductile failure (yield). Depending on the conditions most materials can fail in a brittle or ductile manner or both. However, for most practical situations, a material may be classified as either brittle or ductile.

Mudcracks are sedimentary structures formed as muddy sediment dries and contracts. Crack formation also occurs in clay-bearing soils as a result of a reduction in water content.

Carbon nanotube springs are springs made of carbon nanotubes (CNTs). They are an alternate form of high-density, lightweight, reversible energy storage based on the elastic deformations of CNTs. Many previous studies on the mechanical properties of CNTs have revealed that they possess high stiffness, strength and flexibility. The Young's modulus of CNTs is 1 TPa and they have the ability to sustain reversible tensile strains of 6% and the mechanical springs based on these structures are likely to surpass the current energy storage capabilities of existing steel springs and provide a viable alternative to electrochemical batteries. The obtainable energy density is predicted to be highest under tensile loading, with an energy density in the springs themselves about 2500 times greater than the energy density that can be reached in steel springs, and 10 times greater than the energy density of lithium-ion batteries.

Concrete is a brittle material and can only withstand small amount of tensile strain due to stress before cracking. When a reinforced concrete member is put in tension, after cracking, the member elongates by widening of cracks and by formation of new cracks.

Creep and shrinkage of concrete are two physical properties of concrete. The creep of concrete, which originates from the calcium silicate hydrates (C-S-H) in the hardened Portland cement paste, is fundamentally different from the creep of metals and polymers. Unlike the creep of metals, it occurs at all stress levels and, within the service stress range, is linearly dependent on the stress if the pore water content is constant. Unlike the creep of polymers and metals, it exhibits multi-months aging, caused by chemical hardening due to hydration which stiffens the microstructure, and multi-year aging, caused by long-term relaxation of self-equilibrated micro-stresses in the nano-porous microstructure of the C-S-H. If concrete is fully dried, it does not creep, but it is next to impossible to dry concrete fully without severe cracking.

In continuum mechanics an eigenstrain is any mechanical deformation in a material that is not caused by an external mechanical stress, with thermal expansion often given as a familiar example. The term was coined in the 1970s by Toshio Mura, who worked extensively on generalizing their mathematical treatment. A non-uniform distribution of eigenstrains in a material leads to corresponding eigenstresses, which affect the mechanical properties of the material.

<span class="mw-page-title-main">Ground (art)</span> Term in art

In visual arts, the ground is a prepared surface that covers the support of the picture and underlies the actual painting. Occasionally the term is also used in a broad sense to designate any surface used for painting, for example, paper for watercolor or plaster for fresco.

References

1 2 3 4 5 Bucklow, Spike (1997). "The Description of Craquelure Patterns". Studies in Conservation. 42 (3): 129–140. doi:10.2307/1506709. JSTOR 1506709.
1 2 3 4 5 6 7 8 9 10 Giorgiutti-Dauphine, Frederique (2016). "Painting cracks: A way to investigate the pictorial matter". Journal of Applied Physics. 120 (6): 065107. Bibcode:2016JAP...120f5107G. doi:10.1063/1.4960438.
↑ Krzemien, Leszek (2016). "Mechanism of craquelure pattern formation on panel paintings". Studies in Conservation. 61 (6): 324–330. doi:10.1080/00393630.2016.1140428. S2CID 138963171.
↑ Aurand, Alice (18 April 2018). "Understanding the moisture induced fatigue damage in panel paintings: a methodological approach for quantifying the role of preparatory layers in overall response". Physical Issues in the Conservation of Paintings: Monitoring, Documenting, and Treatment– via HAL.
1 2 Hunt, David; Uzielli, Luca; Mazzanti, Paola (May–June 2017). "Strains in gesso on painted wood panels during humidity changes and cupping". Journal of Cultural Heritage. 25: 163–169. doi:10.1016/j.culher.2016.11.002. ISSN 1296-2074.
↑ Hays, Scott (July 2000). "Being Salvador Dali". Orange Coast .
1 2 Harris, Bronwyn. "Craquelure". Home Institute. Retrieved 2010-10-17.
1 2 Macchia, Andrea (2015). "White zinc in linseed oil paintings: chemical, mechanical, and aesthetic aspects". Periodico di Mineralogica. 84: 483–495.
↑ Ward, 149
↑ Vainker, 101, 107–108
↑ British Museum page, PDF.94 (expand two sets of comments); Krahl, Regina: Oxford Art Online, section "Guan and Ge wares" in "China, §VIII, 3: Ceramics: Historical development"
↑ Kerr, Rose, Needham, Joseph, Wood, Nigel, Science and Civilisation in China: Volume 5, Chemistry and Chemical Technology, Part 12, Ceramic Technology, p. 266, 2004, Cambridge University Press, ISBN 0521838339, 9780521838337, google books
↑ "Tutorial: Add Craquelure to Your Digital Oils". Digital Image. Archived from the original on 2011-08-30. Retrieved 2010-10-17.
↑ Computational forensics : 5th International Workshop, IWCF 2012, Tsukuba, Japan, November 11, 2012 and 6th International Workshop, IWCF 2014, Stockholm, Sweden, August 24, 2014, Revised selected papers. Garain, Utpal,, Shafait, Faisal,, IWCF (Workshop) (6th : 2014 : Stockholm, Sweden). Cham. 26 June 2015. ISBN 9783319201252. OCLC 912553886.{{cite book}}: CS1 maint: location missing publisher (link) CS1 maint: others (link)

Sources

Bucklow, Spike, "A Stylometric Analysis of Craquelure", Computers and the Humanities, Vol. 31, No. 6 (1997/1998), pp. 503–521, Springer, JSTOR
Vainker, S.J., Chinese Pottery and Porcelain, 1991, British Museum Press, 9780714114705
Ward, Gerald W.R. (ed), Grove Encyclopedia Of Materials and Techniques in Art, 2008, Oxford University Press, ISBN 0195313917, 9780195313918, google books

External links

The classification of craquelure Archived 2013-07-25 at the Wayback Machine , Research at the Hamilton Kerr Institute, University of Cambridge

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.

[:0-1] 1 2 3 4 5 Bucklow, Spike (1997). "The Description of Craquelure Patterns". Studies in Conservation. 42 (3): 129–140. doi:10.2307/1506709. JSTOR 1506709.

[:1-2] 1 2 3 4 5 6 7 8 9 10 Giorgiutti-Dauphine, Frederique (2016). "Painting cracks: A way to investigate the pictorial matter". Journal of Applied Physics. 120 (6): 065107. Bibcode:2016JAP...120f5107G. doi:10.1063/1.4960438.

[3] Krzemien, Leszek (2016). "Mechanism of craquelure pattern formation on panel paintings". Studies in Conservation. 61 (6): 324–330. doi:10.1080/00393630.2016.1140428. S2CID 138963171.

[4] Aurand, Alice (18 April 2018). "Understanding the moisture induced fatigue damage in panel paintings: a methodological approach for quantifying the role of preparatory layers in overall response". Physical Issues in the Conservation of Paintings: Monitoring, Documenting, and Treatment– via HAL.

[:2-5] 1 2 Hunt, David; Uzielli, Luca; Mazzanti, Paola (May–June 2017). "Strains in gesso on painted wood panels during humidity changes and cupping". Journal of Cultural Heritage. 25: 163–169. doi:10.1016/j.culher.2016.11.002. ISSN 1296-2074.

[6] Hays, Scott (July 2000). "Being Salvador Dali". Orange Coast .

[homeinstitute-7] 1 2 Harris, Bronwyn. "Craquelure". Home Institute. Retrieved 2010-10-17.

[:3-8] 1 2 Macchia, Andrea (2015). "White zinc in linseed oil paintings: chemical, mechanical, and aesthetic aspects". Periodico di Mineralogica. 84: 483–495.

[Ward,_149-9] Ward, 149

[10] Vainker, 101, 107–108

[11] British Museum page, PDF.94 (expand two sets of comments); Krahl, Regina: Oxford Art Online, section "Guan and Ge wares" in "China, §VIII, 3: Ceramics: Historical development"

[12] Kerr, Rose, Needham, Joseph, Wood, Nigel, Science and Civilisation in China: Volume 5, Chemistry and Chemical Technology, Part 12, Ceramic Technology, p. 266, 2004, Cambridge University Press, ISBN 0521838339, 9780521838337, google books

[digicraq-13] "Tutorial: Add Craquelure to Your Digital Oils". Digital Image. Archived from the original on 2011-08-30. Retrieved 2010-10-17.

[14] Computational forensics : 5th International Workshop, IWCF 2012, Tsukuba, Japan, November 11, 2012 and 6th International Workshop, IWCF 2014, Stockholm, Sweden, August 24, 2014, Revised selected papers. Garain, Utpal,, Shafait, Faisal,, IWCF (Workshop) (6th : 2014 : Stockholm, Sweden). Cham. 26 June 2015. ISBN 9783319201252. OCLC 912553886.{{cite book}}: CS1 maint: location missing publisher (link) CS1 maint: others (link)

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

[9]

[10]

[11]

[12]

[13]

[14]