Deterioration Patterns Wallpaintings: Difference between revisions

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Author: [[user:NRiedl|Nicole Riedl]]<br>
Author: [[user:NRiedl|Nicole Riedl]]<br>
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English Translation by [[user:Hschwarz|Hans-Jürgen Schwarz]] and[[user:SLeithaeuser|Sandra Leithäuser]]<br>
English Translation by [[user:Hschwarz|Hans-Jürgen Schwarz]] and [[user:SLeithaeuser|Sandra Leithäuser]]<br>


back to [[Decay Pattern]]
back to [[Deterioration Patterns]]


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== Examples of damage by salt progression ==
== Examples of damage by salt crystallization ==


== Calcareous concretions (sinter crusts) ==
== Calcareous concretions (sinter crusts) ==
[[file:Nehren Kalksinterkruste.jpg|thumb|300px|left| Calcareous concretion, Roman wall-painting, grave chamber, Nehren]]
[[file:Nehren Kalksinterkruste.jpg|thumb|300px|left| Calcareous concretion, Roman wall-painting, grave chamber, Nehren]]
[[file:Kalksinterkruste NWW Nehren.jpg|thumb|300px|right| Calcareous concretion, Roman wall-painting, grave chamber Nehren]]
[[file:Kalksinterkruste NWW Nehren.jpg|thumb|300px|right| Calcareous concretion, Roman wall-painting, grave chamber Nehren]]
Precipitation of calcium carbonate on the surface of wall paintings begins by a fine white veil and may continue to form a white, dense calcareous concretion. It is characterized by a high stability and strong bond with the painting. The vapor permeability of the wall painting is reduced and the layered crust deposits affects the aesthetic appearance considerably.
Precipitation of calcium carbonate on the surface of wall paintings generally begins by the formation of a fine white veil and may continue to form a white, dense calcareous concretion. It is characterized by its high stability and strong bonding with the painting. The water vapor permeability of the wall painting is reduced with the negative consequences that this may induce and the layered crust deposit(s) considerably affects their aesthetic appearance.
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== Cauliflower crust ==
== Framboidal efflorescence (cauliflower crust) ==
[[file:Blumenkohlkruste Nehren NWW Detail.jpg|thumb|300px|left|Cauliflower crust, grave chamber Nehren]]
[[file:Blumenkohlkruste Nehren NWW Detail.jpg|thumb|300px|left|Framboidal efflorescence, grave chamber Nehren]]
[[file:Blumenkohlkruste Nehren NWW.jpg|thumb|300px|right|Cauliflower crust, grave chamber Nehren]]
[[file:Blumenkohlkruste Nehren NWW.jpg|thumb|300px|right|Framboial efflorescence, grave chamber Nehren]]
The formation of firmly adhering pustules and stable crust deposits, is a characteristic of the cauliflower crust. The composition may consist of calcium carbonate or calcium sulphate. Depending on the contaminants present, the cauliflower crusts appear whitish, yellowish, reddish or brownish. Biogenic precipitate can be stored within the crust deposits.
The formation of firmly adhering framboidal efflorescence is characteristic for some conditions. The composition may consist of calcite (calcium carbonate) or gypsum (calcium sulfate dihydrate). Depending on the contaminants present, the efflorescence may appear whitish, yellowish, reddish or brownish. Biogenic material may be included within the crust deposits as they form.
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== Hygroscopic salts ==
== Hygroscopic salts ==
[[file:Gipskruste Hygroskopisch.jpg|thumb|300px|left|Gypsum crust, hygroscopic, grave chamber Nehren]]
[[file:Gipskruste Hygroskopisch.jpg|thumb|300px|left|Gypsum crust and hygroscopic salts, grave chamber Nehren]]
[[file:Salzkruste Hygroskopisch Nehren.jpg|thumb|300px|right|Gypsum crust, hygroscopic, grave chamber Nehren]]
[[file:Salzkruste Hygroskopisch Nehren.jpg|thumb|300px|right|Gypsum crust and hygroscopic salts, grave chamber Nehren]]
Darkened areas within the layers of crust deposits are visible alongside fissures in the paint layer and the topcoat of the plaster. Increased humidity, originating from the plaster or the ambient air, is bound by the salt crystals and appears macroscopically as a dark, blotched composition.
The photograph shows darkened areas along fissures in the paint layer and topcoat of the plaster that also has crust deposits on it. This is caused by the presence of hygroscopic salts  that will tend to bind any moisture available in the plaster itself or originating from the ambient air. The moisture film will reflect light more giving the surface its darker appearance.  
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[[file:PulvrigeSalzkristalle-01.jpg|thumb|300px|left| Powdery salt efflorescence, sodium sulfate, grave chamber Nehren]]
[[file:PulvrigeSalzkristalle-01.jpg|thumb|300px|left| Powdery salt efflorescence, sodium sulfate, grave chamber Nehren]]
[[file:PulvrigeSalzkristalle-Natriumsulfat.jpg|thumb|300px|right| Powdery salt efflorescence, sodium sulfate, grave chamber Nehren]]
[[file:PulvrigeSalzkristalle-Natriumsulfat.jpg|thumb|300px|right| Powdery salt efflorescence, sodium sulfate, grave chamber Nehren]]
White, loosely adhering salt efflorescence on the plaster and the paint surface. A characteristic of this efflorescence is the formation of small crystalline, soft, powdery salts, which can differ considerably in their chemical composition. The example shows sodium sulfate deposits on a repair plaster made of trass cement.
White, loosely adhering salt efflorescence on the plaster and the paint surface. It is characterized by small crystalline, soft, powdery efflorescence which may be formed by several different salts. The example shows sodium sulfate deposits on a repair plaster made with trass cement.
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== Scaling due to salt activity ==
== Scaling due to salt crystallization ==
[[file:Schalenbildung Nehren-01.jpg|thumb|300px|left|Scaling, grave chamber Nehren]]
[[file:Schalenbildung Nehren-01.jpg|thumb|300px|left|Scaling, grave chamber Nehren]]
[[file:Schalenbildung Nehren-02.jpg|thumb|300px|right|Scaling, grave chamber Nehren]]
[[file:Schalenbildung Nehren-02.jpg|thumb|300px|right|Scaling, grave chamber Nehren]]
The crystallizing salts burst the plaster structure. During the phase transition from liquid salt solution to the formation of salt crystals, an expansion takes place and pressure is applied to the adjacent plaster matrix. Hence,  entire layers of plaster are lifted from the substructure and become crumbly and fragile.
The crystallizing salts can detach the paint layer and even the topcoat of the plaster. This occurs as a result of the liquid to solid phase transition during salt crystallization so that depending on where the salts crystals form, a thinner or a thicker layer may be detached.  
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[[Category:Riedl,Nicole]][[Category:Decay Pattern:Wall Paintings]] [[Category:R-HJuling]] [[Category:R-CBlaeuer]] [[Category:inReview]]
[[Category:Riedl,Nicole]][[Category:Decay Pattern:Wall Paintings]] [[Category:R-HJuling]] [[Category:R-CBlaeuer]] [[Category:approved]]

Latest revision as of 11:00, 18 November 2013

Author: Nicole Riedl

English Translation by Hans-Jürgen Schwarz and Sandra Leithäuser

back to Deterioration Patterns


Examples of damage by salt crystallization[edit]

Calcareous concretions (sinter crusts)[edit]

Calcareous concretion, Roman wall-painting, grave chamber, Nehren
Calcareous concretion, Roman wall-painting, grave chamber Nehren

Precipitation of calcium carbonate on the surface of wall paintings generally begins by the formation of a fine white veil and may continue to form a white, dense calcareous concretion. It is characterized by its high stability and strong bonding with the painting. The water vapor permeability of the wall painting is reduced with the negative consequences that this may induce and the layered crust deposit(s) considerably affects their aesthetic appearance.

Framboidal efflorescence (cauliflower crust)[edit]

Framboidal efflorescence, grave chamber Nehren
Framboial efflorescence, grave chamber Nehren

The formation of firmly adhering framboidal efflorescence is characteristic for some conditions. The composition may consist of calcite (calcium carbonate) or gypsum (calcium sulfate dihydrate). Depending on the contaminants present, the efflorescence may appear whitish, yellowish, reddish or brownish. Biogenic material may be included within the crust deposits as they form.

Hygroscopic salts[edit]

Gypsum crust and hygroscopic salts, grave chamber Nehren
Gypsum crust and hygroscopic salts, grave chamber Nehren

The photograph shows darkened areas along fissures in the paint layer and topcoat of the plaster that also has crust deposits on it. This is caused by the presence of hygroscopic salts that will tend to bind any moisture available in the plaster itself or originating from the ambient air. The moisture film will reflect light more giving the surface its darker appearance.

Powdery salt deposits[edit]

Powdery salt efflorescence, sodium sulfate, grave chamber Nehren
Powdery salt efflorescence, sodium sulfate, grave chamber Nehren

White, loosely adhering salt efflorescence on the plaster and the paint surface. It is characterized by small crystalline, soft, powdery efflorescence which may be formed by several different salts. The example shows sodium sulfate deposits on a repair plaster made with trass cement.

Scaling due to salt crystallization[edit]

Scaling, grave chamber Nehren
Scaling, grave chamber Nehren

The crystallizing salts can detach the paint layer and even the topcoat of the plaster. This occurs as a result of the liquid to solid phase transition during salt crystallization so that depending on where the salts crystals form, a thinner or a thicker layer may be detached.