glossary of damages of stone

7/27/2019 Glossary of Damages of Stone

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Glossary Of Damages Of Stone

A

Alteration: The material that necessary does not imply a worsening ofitcharacteristics from the point of view of conservation.

Alveolization: Formation of cavities on the stone surface which may beinterconnected and may have variable shapes and sizes. Alveolization isa kind of differential weathering caused due to in homogeneties inphysical or chemical properties of stone. It may occur with other

degradation patterns such as granular disintegration or scaling.

Abrasion:Erosion due to wearing down or rubbing away by means of

friction or to the impact of particles.

B

Blistering: Separated, Air-filled raised hemispherical elevations on theface of stone resulting from a detachment of an outer stone layer.

Bursting: local loss of the stone suface usually manifesting in the formof an irregularly sided crater. Bursting is sometimes preceded by starshaped face-fracturing. This deterioration is dur to the increase involume of mineral inclusions naturally contained in the stone andsituated near its surface.

Bleaching: The gain in value due to chemical weathering of minerals,extraction of colouring matter or loss of polish is known as bleaching.

C

Crack: Individual fissure, clearly visible by the naked eye resulting fromseparation from one part to another.

Craquele: Network of minor cracks also called as crack network.


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Crumbling: Detachment of aggregrates of grains from the substrate iscalled crumbling. These aggregates are generally limited in size(lessthan 2cm). this size depends on the nature of the stone and itsenvironment.

Chipping: breaking off of pieces, called chips from the edge of theblock.

Contour Scaling: Scaling in which the interface with the sound part ofthe stone is parallel to the stone surface. In the case of flat surfacecontour scaling may be called as SPALLING.

Cut:: Loss of material due to the action of an edge tool. It can haveappearance of an excavated cavity, an incision or a missing edge.

Crust:The accumulation of materials on the surface is called as crust. A

crust may include exogenic deposits in combination with materialsderived from the tone. Crusts have homogeneous thickness thusreplicate the stone surface.

DDamage:: human perception of the loss of value due to decay.

Decay: : Any chemical or physical modification of the intrinsic stoneproperties leading to a loss of value or to the impairment of use.

Degradation: Decline in condition, quality or functional capacity.

Deterioration: Process of making or becoming lower worse or lower in

quality, value, character.

Deformation:: Change in shape without losing integrity, leading tobending or twisting of a stone block.

Delamination: : detachment process affecting laminated stones. Itcorresponds to a physical separation into one or several layers followingthe stone laminae. The thickness and shape of the layers are variable.The layers may be oriented in any directions with regards to the stonesurface.


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Disintegration: Detachment of single grains or aggregates of grains. Itaffects the surface of the stone or it can occur in depth. Damagegenerally starts from the surface of the material.

Differential Erosion:Differential erosion occurs when erosion does notproceed at the same rate from one area of the stone to the other, as aresult the stone deteriorates irregularly. This feature is found onheterogeneous or less porous stones. It may also occur due to a certainlichen attack on calcitic stones. Differential erosion is caused due to lossof components and loss of matrix.

Deposit: : accumulation of exogenic material of variable thickness. Adeposit can be described for colour, morphology, size and origin,

Discolouration: the change of stone colour in one of the three colourparameters of hue, value and chroma is called discolouration. It isfrequently caused by salts, by corrosion of metals, by microorganismsand by exposure to fire.

EExfoliation:: Detachment of multiple thin stone layers that are sub-

parallel to the stone surface. The layers may bend, twist in a similar wayto book pages.

Erosion: : Loss of original surface , leading to smoothed shapes can bedefined as erosion.

Efflorescence: The whitish powdery or whisker like crystals on thesurface which are poor cohesive and commonly made of soluble saltcrystals. Efflorescence is the result of evaporation of saline water

present in the porous structure of the stone. They are often constitutedof soluble salts like sodium chloride(NaCl), magnesium sulphate(MgSo4),calcitr(CaCo3), barium sulphate(BaSo4) and amorphoussilica(SiO2.H2O).

Encrustation:: It is a compact, hard mineral outer layer adhering tothe stone. Its surface morphology and colour are usually different fromthose of the stone. They are mostly deposits of materials mobilized bywater percolation.


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F

Fracture: : Line that completely crosses the stone piece.

Fragmentation:The complete or partial breaking up of a stone, intoportions of variable dimensions that are irregular in form, thickness andvolume. Fragmentation may occasionally affect the entire stone blockand may follow discontinuity planes. Fragmentation may be found whenstone blocks are subjected to an overload.

Flaking: : scaling in thin flat or curved scales of submillimetric tomillimetric thickness, organised as fish scales.

Film: It is a coating or covering layer of organic nature which ishomogenous. The film is opaque or translucent. Paint layers, waterrepellants, protective agents and sealants are considered as film.

GGranular Disintegration: : It occurs in sandstone and granites. Itproduces debris known as rock meal and it can often be seenaccumulating on the foot of the wall which has been deteorating. In case

of crystalline marbles thermal stresses are known to be the main reasonfor granular disintegration thus leading occasionallt to deformationprocesses.

Graffiti:Engraving, scratching, cutting or application of paint, ink orsimilar matter on the stone surface is called as graffiti. Sometimes it iscaused by act of vandalism.

K

Keying:: Impact damage resulting from hitting a surface with a pointedtool, inorder to get an irregular surface which will assist the adhesion ofan added material.

M

Mechanical Damage:Loss of stone material due to a mechanicalaction.

Microkarst: Network of small interconnected depressions of millimetric

to centrimetric scale, sometimes looking like hydrographic network.


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Microkarst patterns are due to a partial or selective dissolution ofcalcareous stone surfaces exposed to water run off.

Missing Part:: Empty space, located in the place of some formerly

existing stone part.

PPowdering: Disintegration of finely grained stones is called aspowdering.

Peeling:: Shedding, coming off or partial detachment of a superficiallayer having the aspect of a film or coating which has been applied onthe stone surface.

Perforation:A single or series of surface punctures, holes or gaps made

by a sharp tool or created by an animal. Perforations are deeper thanwide, and penetrate into the body of the stone.

Pitting:: They are point like shallow cavities. The pits generally haveconical or cylindrical shape and are not interconnected, althoughtransition patterns to interconnected pits are observed. It can bebiogenically or chemically induced especially on carbonate stones.

Patina:: Chromatic modification of the material, generally resulting

from natural or artificial ageing and not involving in most cases visiblesurface deterioration.

R

Rounding:preferential erosion of originally angular stone edges leading

to a distinctly rounded profile. Rounding can especially be observed onstones which deteriorate through granular disintegration.

Roughening:: Selective loss of small particles from an originallysmooth stone surface. Roughening can appear progressively in case oflong term deterioration processor instantly in case of inappropriateactions.

SStar-Crack: Crack having the form of a star. Rusting of Iron andmechanical damage are responsible for this type of damage.


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Splitting: : Fracture of a stone along planes of weakness such asmicrocracks or clay/silt layers, in case structural elements are orientedvertically.

Sugaring: it is a term used for disintegration of fine white crystallinemarble.

Sanding: It is used to describe granular disintegration of sandstone andgranite.

Splintering: It is used to describe granular disintegration of sandstoneand granite.

Scaling:: Detachment of stone as a scale or a stack of scales, notfollowing any stone structure and detaching like fish scales or parallel tothe stone surface. The thickness of a scale is generally of millimetric tocentimetric scale and is negligeable compared to its surface dimension.The plane of detachment of the scale is located near the stone surface.

Scratch: : Manually induced superficial and line-like loss of material dueto the action of a pointed object.

Soiling: Deposit of a very thin layer of exogenous particles giving adirty appearance to the stone surface. Soiling is caused by atmosphericpollutants, particles transported by running water and heatingconvection.

Subflorescence: Its a poorly adhesive soluble salt, commonly whitelocated under the stone surface. It is a result of evaporation of salinewaterpresent in the porous structure of the stone.

Damages Caused By Microorganisms

Biological Colonization: Colonization of stone by plants andmicroorganisms such as bacteria, cyanobacteria, algae, fungi and lichen.It also includes influences by other organisms nesting on and in thestones. This term is used when a mixture of different types of organismsare present on a stone and are not distinguishable between each other.


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Algae:Algae are microscopic vegetal organisms without stems or leaveswhich can be seen indoors and outdoors, as powdery or viscousdeposits. Algae form red, green, brown or black veil of zones and can befound in situations where the substrate remains moistened for long

periods of time. Depending on environmental conditions and substratetype algae may form solid layers or smooth films. On monuments algaeare constituted of unicellular to pluricellular clusters and they never formmicroorganisms

Lichen: Vegetal organism forming crusty or bushy patches, oftenhaving a leathery appearance growing generally on the outside part ofthe building. Lichen are most commonly grey, yellow, orange or blackand show no differentiation into stem, root and leaf. All lichen represent

symbiotic growth of a fungus and green alga or a cyanobacterium.Lichen is a common feature on outdoor stone and is generally bestdeveloped under clean air conditions, but growth may be facilitated bycertain pollutants such as nitrogen oxides derived from vehicle pollutionor agriculture.

Moss: Vegetal organism forming small soft and green cushions ofcentimetric size. Mosses generally look like dense micro leaves tightlypacked together. Mosses often grow on stone surface open cavities,cracks and in any place permanently and frequently wet and usuallyshady. Mosses often change morphology and colour under lack orexcess of water. During dry periods of the year the cushions shrink,become harder and brittle, and their colour turns brown.

Mould: Microscopic fungus which colonies, to the naked eye look likelook like a downy film or a network or star-like patches of filaments ofdiverse colours of white, grey and black. Mould often creates serious

damage by chemical and mechanical action and heavy discolouration. Asthe metabolism of mould necessitates organic substrate mould oftendevelops on algal metabolic products found on stone. Organic pollutionof the atmosphere also favours mould growth.

Plant:Vegetal living being, having, when complete, root, stem andleaves, though sometimes consisting only of a single leafy expansion. Ifbuildings are not maintained plants will eventually colonise places wherewater is accessible, extending roots into joints and fractures. As the

roots grow they can widen these joints and crack and break the stone.


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They also contribute to keep the area damp, this exacerbates otherprocesses such as salt deterioration.

glossary of damages of stone

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