{no title found}

Erosion due to wearing down or rubbing away by means of friction, or to the impact of particles.

Algae are microscopic vegetal organisms without stem or leaves which can be seen outdoors and indoors, as powdery or viscous deposits (thickness : tenth of mm to several mm). Algae form green, red, brown, or black veil like zones and can be found mainly in situations where the substrate remains moistened for long periods of time. Depending on the environmental conditions and substrate type, algae may form solid layers or smooth films. On monuments, algae are constituted of unicellular to pluricellular clusters, and they never form macroorganisms.

Describes a deterioration pattern even if there is no active material loss at the time the object is described.

Colonization of the stone by plants and micro-organisms such as bacteria, cyanobacteria, algae, fungi and lichen (symbioses of the latter three). Biological colonization also includes influences by other organisms such as animals nesting on and in stone.

Kind of crust developing generally on areas protected against direct rainfall or water runoff in urban environment. Black crusts usually adhere firmly to the substrate. They are composed mainly of particles from the atmosphere, trapped into a gypsum matrix.

Separated, air-filled, raised hemispherical elevations on the face of stone resulting from the detachment of an outer stone layer. This detachment is not related to the stone structure.

Local loss of the stone surface from internal pressure usually manifesting in the form of an irregularly-sided crater.

Breaking off of pieces, called chips, from the edges of a block.

change in hue, value and/or a gain in chroma

Deformation with a concave bulge.

scaling in which the interface with the sound part of the stone is parallel to the stone surface. In the case of flat surfaces, contour scaling may be called spalling. Case hardening is a synonym of contour scaling.

Deformation with a convex bulge.

Describes a deterioration pattern even if there is no active material loss at the time the object is described.

Individual fissure, clearly visible by the naked eye, resulting from separation of one part from another.

Network of minor cracks also called crack network. The term crazing is not appropriate for stone, as this term should be used for describing the development of a crack network on glazed terracotta.

Detachment of aggregates of grains from the substrate. These aggregates are generally limited in size (less than 2 cm). This size depends on the nature of the stone and its environment.

Generally coherent accumulation of materials on the surface. A crust may include exogenic deposits in combination with materials derived from the stone. A crust is frequently dark coloured (black crust) but light colours can also be found. Crusts may have an homogeneous thickness, and thus replicate the stone surface, or have irregular thickness and disturb the reading of the stone surface details.

Loss of material due to the action of an edge tool. It can have the appearance of an excavated cavity, an incision, a missing edge, etc...Tool marks can be considered as special kinds of cuts but should not be considered as damage features.

Change in shape without losing integrity, leading to bending, buckling or twisting of a stone block.

Detachment process affecting laminated stones (most of sedimentary rocks, some metamorphic rocks). It corresponds to a physical separation into one or several layers following the stone laminae. The thickness and the shape of the layers are variable. The layers may be oriented in any direction with regards to the stone surface.

Accumulation of exogenic material of variable thickness. Some examples of deposits : splashes of paint or mortar, sea salt aerosols, atmospheric particles such as soot or dust, remains of conservation materials such as cellulose poultices, blast materials, etc.

Removal of material from the damaged stone.

occurs when erosion does not proceed at the same rate from one area of the stone to the other. As a result, the stone deteriorates irregularly. This feature is found on heterogeneous stones containing harder and/or less porous zones. It may also occur as a result of selective lichen attack on calcitic stones. Differential erosion is generally found on sedimentary and volcanic stones. Differential erosion is synonymous with relief formation, i.e. the formation of irregularities on the stone surface. Differential erosion may result in loss of components or loss of matrix of the stone

Accumulation of exogenic material of variable thickness. Some examples of deposits : splashes of paint or mortar, sea salt aerosols, atmospheric particles such as soot or dust, remains of conservation materials such as cellulose poultices, blast materials, etc.

Detachment of single grains or aggregates of grains.

Generally whitish, powdery or whisker-like crystals on the surface. Efflorescences are generally poorly cohesive and commonly made of soluble salt crystals.

Loss of original surface, leading to smoothed shapes.

detachment of multiple thin stone layers (cm scale) that are sub-parallel to the stone surface. The layers may bend or twist in a similar way as book pages.

Thin covering or coating layer generally of organic nature, generally homogeneous, follows the stone surface. A film may be opaque or translucent.

scaling in thin flat or curved scales of submillimetric to millimetric thickness, organized as fish scales.

Crack that crosses completely the stone piece

The complete or partial breaking up of a stone, into portions of variable dimensions that are irregular in form, thickness and volume.

hollow place in the stone surface, hole

A damage that affects a gap (the interface area between two stones).

Generally whitish, powdery or whisker-like crystals on the surface. Efflorescences are generally poorly cohesive and commonly made of soluble salt crystals.

Occurs in granular sedimentary (e.g. sandstone) and granular crystalline (e.g. granite) stones. Granular disintegration produces debris referred to as rock meal and can often be seen accumulating at the foot of a wall actively deteriorating. If the stone surface forms a cavity (coving), the detached material may accumulate through grav ity on the lower part of the cavity. The grain size of the stone determines the size of the resulting detached material.

Minor crack with width dimension < 0.1 mm

Mechanical damage due to the impact of a projectile (bullet, shrapnel) or of a hard tool.

Natural black to brown thin layer enriched in iron/clay minerals, which can be found on iron containing sandstones. This kind of patina is generally observed in outdoor environments, and develops quite uniformly on the stone surface.

Impact damage resulting from hitting a surface with a pointed tool, in order to get an irregular surface which will assist the adhesion of an added material, a mortar for instance.

Vegetal organism forming rounded millimetric to centimetric crusty or bushy patches, often having a leathery appearence, growing generally on outside parts of a building. Lichen are most commonly grey, yellow, orange, green or black and show no differentiation into stem, root and leaf.

Loss of stone material clearly due to a mechanical action.

Network of small interconnected depressions of millimetric to centrimetric scale, sometimes looking like hydrographic network. Microkarst patterns are due to a partial and/or selective dissolution of calcareous stone surfaces exposed to water run-off.

corresponds to the darkening (lower hue) of a surface due to dampness.

Pflanzlicher Organismus, der kleine, weiche grüne Kissen von Zentimetergröße bildet. Moose sehen allgemein wie dichte Mikroblätter (Sub - bis Millimetergröße) aus, die dicht zusammen gepackt sind. Moose wachsen oft auf der Steinoberfläche in offenen Aushöhlungen, Rissen oder an anderen Stellen, die andauernd oder häufig feucht (Mauerwerksfugen) und gewöhnlich schattig sind.

Microscopic fungus colonies which, to the naked eye, look like a downy film or a network or star-like millimetric patches of filaments of diverse colours (white, grey, black).

Orange to brown thin layer enriched in calcium oxalates. This kind of patina may be found in outdoor environments, often on marble and limestone substrates.

Chromatic modification of the material, generally resulting from natural or artificial ageing and not involving in most cases visible surface deterioration.

Shedding, coming off, or partial detachment of a superficial layer (thickness : submillimetric to millimetric) having the aspect of a film or coating which has been applied on the stone surface.

Point-like millimetric or submillimetric shallow cavities. The pits generally have a cylindrical or conical shape and are not interconnected, although transition patterns to interconnected pits can also be observed.

Vegetal living being, having, when complete, root, stem, and leaves, though consisting sometimes only of a single leafy expansion (e.g. tree, fern, herb).

Selective loss of small particles from an originally smooth stone surface. The substrate is still sound. Roughening can appear either progressively in case of long term deterioration process (for instance in case of granular disintegration), or instantaneously in case of inappropriate actions, such as aggressive cleaning.

Preferential erosion of originally angular stone edges leading to a distinctly rounded profile. Rounding can especially be observed on stones which preferably deteriorate through granular disintegration, or when environmental conditions favor granular disintegration.

Crust composed of soluble salts, which develop in the presence of high salt levels, and form from wetting and drying cycles.

Detachment of stone as a scale or a stack of scales, not following any stone structure and detaching like fish scales or parallel to the stone surface. The thickness of a scale is generally of millimetric to centimetric scale, and is negligeable compared to its surface dimension.

Manually induced superficial and line-like loss of material due to the action of some pointed object. It can be accidental or intentional. Usually it appears as a more or less long groove. Tool marks can have the appearance of scratches, but should not be taken as damage features.

A single crack, whichdoes not appear in a group of smaller cracks.

Deposit of a very thin layer of exogenous particles (eg. soot) giving a dirty appearance to the stone surface.

Detachment of sharp, slender pieces of stone, split or broken off from the main body.

Fracturing of a stone along planes of weakness such as microcracks or clay/silt layers, in cases where the structural elements are orientated vertically. For instance, a column may split into several parts along bedding planes if the load above it is too high.

kind of discolouration of limited extent and generally of unattractive appearance.

Crack having the form of a star. Rusting iron or mechanical impact are possible causes of this type of damage.

A damage that affects a stone component

Describes a deterioration pattern even if there is no active material loss at the time the object is described.