Conservation and Scientific Research glossary

Abrasion/ abraded:
Damage to the surface caused by rubbing or friction.

Accelerated ageing:
Testing that uses heightened conditions of heat, oxygen, sunlight, vibration, etc. to speed up the normal aging processes of items. This assists CSR to determine how an artefact is likely to age or deteriorate and what measures can be put in place to prevent this. It can also be used on display or storage materials to ensure they do not become volatile as they age.

Accretion/ residues:
Deposit of foreign matter on the surface, e.g. mud, usually stuck to the surface. Residues are often accretions arising from use e.g. food residues.

Acidic: 
When the material has the property of an acid or contains acidic components. The pH is below 7.

Active corrosion:
Evidence of ongoing deterioration, e.g. with loose powdery, friable, pitted or flaking corrosion/surfaces or colour change. See Corrosion.

Additions:
Any pieces or parts that were added to the original artefact over the course of its history.

Adhesive:
Conservators use several conservation grade glues and adhesives in their work. Some of these include:
•    Corn, wheat or tapioca starch glues
•    Klucel G / E – a non-ionic cellulose ether with a remarkable combination of properties. Often used as a consolidant. See Consolidation.
•    Animal glues from cow or rabbit skin and sturgeon.

Alterations:
Changes made to the object over the course of its history that affect or change its appearance or function.

Ancient repair:
Some objects include historical repairs. These could include patches, rivets, solders, and adhesives, and can sometimes start to deteriorate. Conservators make decisions, along with curators and other stakeholders, about whether to keep or remove historic repairs. Decisions take into account the material nature of the repair, the potential cultural significance of the repair, and the benefits and risks of retaining or removing the repair. The decision is specific to each object. 

Archaeological fresh finds:
Artefacts which have been freshly excavated.

Authenticity:
Within conservation, authenticity refers to the ethical treatment of an object – the conservator must not change the aesthetic or integral meaning of an artefact through treatment.

Backing removal:
Objects are often reinforced by adding a backing such as paper or textiles. Backings can become structurally, chemically or aesthetically deleterious to the object, in which case conservators will remove the backing. There are a number of methods that can be used to remove a backing, depending on the material make-up of the object and the backing.

Bent:
Misshapen with fold or kink in material, out of alignment, often referring to projecting elements such as feathers. There may or may not be a break at the bend.

Blanched (paper):
The opaque, whitish appearance of paint or varnish caused by the leaching out of certain substance or by the pulverisation of paint or varnish under pressure as in a scrape or scratch. In either case minute interruptions within the varnish or medium refract light producing a milky appearance. Moisture often causes blanching.

Bleaching:
Often caused by the sun or chemicals, this can cause damage to objects, but can also be used as a treatment to improve the appearance of paper.

Bleeding:
The separation of pigments, especially dyes, into adjacent areas.

Blisters:
A convex deformation of the surface, hollow underneath. This can be observed in bulging paint for example.

Bloom 
•    Ceramics, glass, metals and stone: areas of white cloudiness on the surface caused by a refraction of light from the presence of small cracks/ surface damage/ or powdery deposit.
•    Organics: bluish white cloudiness often on a painted or varnished surface, caused by moisture penetrating the surface.

Breaks:
A separation between areas of a hard material such as glass, ceramic, wood, stone and other materials, usually caused by a sudden shock and often occurring at weak points. May also be used to describe damage to brittle paper or cardboard, where pieces have been snapped off.

Brittle:
Loss of strength and flexibility, causing the material to break when bent. Paper is said to be brittle when a corner will not withstand two complete folds without breaking. Plastics also become brittle, through the loss of plasticising agents.

Broken/detached/separated:
The object, or element of an object, is in more than one piece.

Broken stitching threads/ bindings (organics):
E.g. splits in seams, or broken threads used to secure parts or decorative elements, such as beads.

Buckling:
Of veneered or inlaid surfaces – material has expanded in size but is fixed in position, so excess bulges or lifts up.

Burns:
Surface damage caused by fire or heat. Burned surfaces are usually black or brown in colour, friable and brittle. There may also be soot and smoke damage, water damage and melting or softening. This term may also be used to describe damage caused by sunlight or chemical pollutants such as light or mat burn.

COSHH (Control of Substances Hazardous to Health):
This is the protocol carried out to ensure safe working practices when using the various materials for conservation treatment and scientific research such as solvents.

CT Imaging (Computerised Tomography):
This combines a series of X-ray views taken from many different angles and computer processing to create cross-sectional images of the interior of an artefact (e.g. a mummy). In some cases, CT images can be combined to create 3D images. CT scan images can provide much more information than X-rays.

Cellulose:
Is a naturally occurring organic compound and forms a basic constituent of plants.

Chalky:
Powdering of the surface.

Chip 
•    Stone: loss of a small amount of material as a result of a mechanical action (e.g. impact).
•    Organics/ metals: marks or flaws made by breaking off or gouging out of a small piece of the object.

Chipped:
Small section or piece cut or broken off from hard material – this implies loss of a small amount of material often exposing fresher looking material underneath.

Cleaning:
There are many different methods for cleaning heritage objects – dry cleaning / wet/ washing. Conservators decide which method would most suit each object.

Clip (from paper conservation):
To hide excess paper or cover the edge of a sheet of paper, for example using a window mount. Not to cut.

Coating (ceramics/ metals/ stone):
A layer or film spread over a surface usually for protection. These may be waxes, natural or synthetic resins.

Collections Care:
The overarching term given to professionals involved with the maintenance and care of a museum or gallery collection.

Concretion/ accretion (ceramics, glass, metals):
A hard surface deposit of a foreign material often from burial.

Conservation:
The profession devoted to the preservation of cultural property for the future.

Conservator:
A professional who, through specialised education, knowledge, training and experience formulates and implements all the activities of conservation in accordance with an ethical code.

Consolidation:
To make a fragile or crumbling material stronger.

Corrosion:
Gradual deterioration of a metal due to chemical processes such as oxidation or the action of a chemical agent. Some corrosion products, like metal patinas, can be protective. Others, like rust, can be harmful.

Corrosion/ tarnish:
Of metal elements used in combination with organic materials: often the organic material exacerbates the corrosion. Rust, or green copper corrosion products can cause staining of the surrounding organic material.

Crack: 
•    Paper: fractures caused by internal or external pressure to a surface. No loss is implied. Visible break in the surface, occurring when paper is creased or embossed; sometimes called 'crazing' in photographs.
•    Stone: (structural) inherent in the matrix of the material, a major weakness. In stone this may be the bedding planes.
•    Organics / stone: narrow openings between two parts of a material that have split or become broken but may not be separated from each other or have suffered loss. Usually used to describe breaks in solid materials such as stone, ceramics and wood. In plastics, refers to splits that follow the grain or direction of manufacture.
•    Ceramics / glass: (fracture/crack) a narrow opening between two parts that have split or become broken but are not separated from each other. Cracks may become unstable if subjected to stress/impact damage. The area gives a dull ringing tone when lightly tapped.

Craquelure/ crazed surface:
Network of (random) cracks in a surface, e.g. painted surface, usually resulting from the surface drying out. Likely to be stable and not flaking.

Crazing (ceramics/ glass):
Occurs as a result of stresses between glaze and underlying body resulting in a fine network of cracks in the glaze. Old crazing tends to be stained and the lines are more obvious while fresh crazing appears as clean cracks through the glaze.

Creases/ wrinkles:
Occur when a flat, sheet-like material such as paper or fabric has been folded over on itself leaving a lasting depression or ridge along the line.

Creasing
Irregular pattern of lines, wrinkles or folds etc. in 2D flexible materials, often clothing or large textiles, barkcloth. Tends to be accidental rather than intentional. Creasing is often described as heavy or light.

Crocking: 
Excess dye rubbing off through friction.

Crumbling:
Object material exhibiting loss of cohesion leading to loss of particulate matter when force is applied.

Crystalline deposits:
Not all white crystalline deposits are salt growth, may also be remains of some applied chemicals, such as pesticides.

Cupping/ elevated edges:
Concavity of islands of paint, leading to protruding or raised edges of the paint flake above the main surface, risk of further deterioration through snagging and catching.

Cupping (paper):
Lifting along the edges of cracks surrounding an island of paint so that the paint surface is bent concavely into the shape of a shallow cup.

Cuts:
Implies damage caused by knife, scissors, or sharp implement, usually the surrounding material is in robust condition.

Decoration (ceramics / glass):
Gilding, glaze, enamel, paint, slip or unfired decoration often found on ceramic or glass objects.

Deformed/ distorted/ misshapen:
Changes in shape and form, detracting from objects original appearance.

Degraded
When objects are weakened or have a loss of tensile strength. Degradation can lead to objects becoming fragile and running the risk of incurring further damage or loss.

Delamination 
•    Organics: separation of layers, may refer to separating of layers joined in construction of the object, may be between layers of same or different materials, or separation within a laminar material, e.g. shell, mica.
•    Paper: linings separating out from one another, usually leaving bubbles where voids are present between layers. This is also referred to as splitting.
•    Ceramics, glass, metals: (also referred to as 'lifting') separation between layers of the original material in which pieces are partially detached or raised e.g. paint.

Dents
Hollows or depressions in the surface of the object, often caused by pressure or an impact.

Deteriorated
•    Ceramics, glass: object in poor condition which may include weathered glaze, deteriorating adhesives, flaking or lifting glaze, unstable gilding, unfired decoration, loose surface material, cracks.
•    Metals: general term to denote poor condition of the object material.

Deterioration (processes of):
All materials follow certain deterioration patterns and processes. By identifying materials, it helps conservators to predict and inhibit these processes.

Dirty:
A deposit of dirt, dust, grime or other contaminant absorbed into the surface and not easily brushed off.

Discolouration/ yellowing/ fading/ darkening:
Permanent change in the colour of the material due to light damage or chemical change, may be overall, may be localised, often can see difference between where material is exposed to light and where covered.

Dismantling:
Conservators may take apart an object and put it back together in order to conserve it.

Distorted:
Shape is changed from its original, natural or intended form.

Dowelling/ joining:
A dowel is a small round wooden peg that is used to strengthen or reinforce a joint – often in organic objects.

Dust:
Particulate material which has settled on the surface of the object and contributes to corrosion, staining and abrasion.

Dusty:
Loose dust and dirt lying on the surface, can be brushed off relatively easily.

Dye transfer:
Spread of dye colour from coloured to uncoloured area. Induced either by water or friction. 

Efflorescence:
Migration of a salt or whitish powdery material to the surface.

Embrittlement:
A loss of flexibility causing the material (e.g. paper, parchment, leather) to break or disintegrate when bent or curled.

Enamel (ceramics/ glass):
Glassy substance, coloured by metallic oxides, applied and fired onto glaze, as decoration.

Environmental conditioning:
The active management and control of environmental factors (e.g. temperature, relative humidity, light exposure) that could accelerate the deterioration of an object through using a variety of passive or mechanical methods. Different material types require different ideal environmental conditions. Through a variety of control methods, we can condition the environment to levels that slow down deterioration.

Faded:
Usually caused by exposure to light. Most obvious when edges of pictures have preserved the original colour due to protection by top mount and exposed areas have faded.

Fatty exudations:
White waxy surface deposit found on skins/leather usually associated with movement of fats coming out of the material often resulting in changes in environment.

Fill:
A material used where an object has lost material. This is either for aesthetic reasons or to stabilise the whole. An inert / conservation grade material which is reversible will always be used. Fills may be coloured and textured to blend in with the original surface. Fills may start to shrink, with cracks appearing along their edges. New fills should be regarded as potential areas of weakness during handling and vulnerable to impact damage.

Fingerprints:
The impression of fingerprints left on an object, sometimes contributing to staining of the surface.

Firing crack (ceramics/ glass):
Caused during the manufacture of an object. They are usually stable but are possible areas of weakness especially if wide or extensive.

Flakes:
Small, thin pieces of varnish, paint or other layers that have become completely detached from the main support material, due to extreme cracking.

Flaking:
An unstable condition in which areas of original material become detached from the main part. See also Lamination and Lifting.

Folded:
An object, or a portion of an object, that has been bent or pressed so that one part is over another.

Fold lines:
Regular sharp straight ridge or groove usually arising from material being folded for long periods of time, usually associated with textiles or large flat and flexible materials such as skins, barkcloth, and plant fibre.

Fourier-Transform Infra-Red Spectroscopy (FTIR):
This is an analytical tool allowing scientists and conservators to determine which molecular structures are present in a material. From this information they can often determine which material was used to construct an object. FTIR is most often used in the analysis and identification of organic compounds such as resins, starches and proteins, all of which are used in the construction of ethnographic objects.

Fragile:
Physically delicate, easily broken, damaged or harmed.

Fragmentary: 
•    CGM, stone: where part of an object is in many small pieces that are completely separated.
•    Organics: extensive damage has occurred leading to the object or material being in many small pieces, either completely separated or partially connected. Also used to describe textiles where there is extensive loss, sometime irregular shaped islands of textile remaining loosely connected following insect infestation.

Fraying
Wearing away and/or unravelling of fabric, leaving loose threads.

Gas Chromatography–Mass Spectrometry (GC-MS):
An analytical tool used to identify materials, especially useful for ancient or very degraded materials.

Gilding (ceramics/ glass):
Gold decoration applied onto the glaze by various techniques. Can be fired and unfired.

Glaze (ceramics/ glass):
Vitreous or glassy coating or surface on ceramics, impervious to liquids.

Grime:
A disfiguring deposit on or engrained in the surface of the material. Also referred to as surface dirt. See Surface dirt.

High Performance Liquid Chromatography (HPLC):
An analytical tool used mainly to identify organic pigments and proteinaceous paint binders.

Holes:
Punctures or cavities in the object caused by a variety of means, not part of the original object.

Incomplete/ missing parts/ losses:
Any element or piece of the object or image that is missing. Can be minor, moderate, or extensive.

Indigenous or historic repairs:
Repairs made during active life of object.

Inert:
Refers to chemically inactive material that has been used in the treatment of an object or the material that the object is stored or packed with.

Ingrained dirt:
Dirt absorbed into the surface and not easily brushed off.

Inlay:
A term used in paper conservation and mounting to refer to a false margin attached to a work of art which enables handling without touching the original.

Inpainting:
Application to the surface of a fill or area of loss. An associated word is 'retouching'. See Re-touching.

Integrated Pest Management (IPM):
This is the term used for the management and prevention of pest infestation within the collection. This refers to monitoring for pests in the collection, treating infestations as well as setting up protocol to reduce the risk of pests entering the building.

Interventive:
When a physical treatment is carried out on an object such as a clean or fill.

Interventive conservation:
This refers to when physical treatment is carried out on an artefact such as re-touching or consolidation. This is opposed to preventive conservation. See Preventative conservation.

Lamination:
Separation between layers of the original material. Can also describe between layers such as pigment and ground. Other associated words include lifting and flaking. See Lifting and Flaking.

Leaching:
The uncontrolled and often undesirable movement of a material e.g. of printing oils in paper.

Lifting:
•    General: a form of deterioration in which pieces of the original material are partially detached or raised. Other words – laminating, flaking. See Lamination and Flaking.
•    Paper: also refers to an object lifting in an uncontrolled manner from materials used to mount the paper object. 

Local cockling:
Smaller distortions in specific areas, such as corners/joints.

Loose:
Parts that are moving or mobile, but not detached or separated.

Loose or mobile elements/ loosened parts (organics):
Parts of the object are loose and can move when they should be fixed, often due to deterioration of joints and fittings, or where different materials are joined together. Also loosening of knots in wood.

Loss:
Area where original material is missing because of damage or deterioration; does not have all parts or details, it is partial.

Lustre (ceramics/ glass):
Decoration consisting of an extremely thin layer of metal applied, and fired, onto the glaze.

Lux:
The unit of illuminance from visible light. High lux levels are harmful to a variety of materials. Conservators monitor and limit the exposure of light sensitive objects e.g. watercolour artworks, by reducing display time and giving them resting time (in the dark).

Manufacturing defects/faults (ceramics/ glass):
Although not a type of damage, they can be points of weakness. Usually caused by the object having a poorly formulated body or glaze, poor construction or firing inconsistencies, for example, minor faults such as pinholes or glaze blemishes.

Mechanical cracks:
Caused by movement or excessive stress.

Micro-excavation:
Laboratory excavation of small- or large-scale soil blocks containing archaeological assemblages
 
Mildew:
Specific type of mould. It can be downy or powdery. Could be seen as yellow spots which then turn brown or a whitish powder that slowly turn yellowish brown and then black.

Mineralised:
Metal is converted wholly or partly into a mineral or inorganic structure/ entirely corroded.

Mineral Preserved Organic Remains (MPO's):
Metallic compounds from a corroding metal object replace structure of organic material such as textile or leather.

Mould: 
•    Ceramics: another word for fungi; may appear as colourful powdery or downy growth on an object's surface, or as black spots.
•    Organics: another word for fungi; mould spores can germinate and grow within organic materials to cause staining and structural weakening. May appear as colourful powdery or downy growth on an object's surface, or as black spots.

Mounting:
Mounts perform a variety of functions for both 2D and 3D objects and are often an intrinsic part of safe display and storage. The materials the mount is made from will also vary, depending on the needs of the object, but will always be formed of materials with a known stability. In the case of Asian paintings, the mount is part of the object itself and cannot be dissociated from the painting e.g. hanging scroll, handscroll, folding screen or thangka. When conservators treat an Asian painting, they also conserve the mount to guarantee safe display, handling, and storage.

Odour:
May indicate mould, or pesticide use, or arising from general deterioration of materials (e.g. musty smell). 

Overpaint:
Term used when the paint is not the original. Overpaint often hides areas of damage.

pH: 
Potential of Hydrogen is a scale used to determine the acidity or basicity of a material, substance or aqueous solution.

Patina:
A surface feature which can be observed on objects. It can form either naturally or through intentional intervention. Protective, stable, lightly corroded, often smooth surface.

Pests:
Damage to objects caused by insects, rodents etc., usually through staining, soiling, and consuming surfaces and organic components. Evidence includes pest residue such as casings and frass (dust-like debris left by wood-eaters) and pest damage such as exit holes, and grazing (partially eaten surfaces).

Pest treatment:
Methods to eradicate any active or potential pest activity present on an object. There are three main method options:
•    Low oxygen (anoxia treatment) – objects are placed in a chamber and the oxygen is slowly removed and replaced with nitrogen which eradicates all stages of insect life cycle (adult insects, larvae and eggs).
•    Low temperature (freezing) – objects are exposed to a minimum of -30°C for 72 hours, the low temperature eradicates all stages of insect life cycle (adult insects, larvae and eggs). 
•    Moisture-controlled heat treatment – objects are exposed to 55˚C for 90 minutes in a humidity-controlled chamber, this eradicates all stages of the insect life cycle (adult insects, larvae and eggs). 

Pitted:
A surface deterioration mainly on metal and glass objects, covered with low areas or depressions.

Porous (ceramics/ glass/ stone):
Absorbent, will let moisture/dirt in. Material which is easily penetrated.

Portable Antiquities Scheme:
The Portable Antiquities Scheme is a DCMS funded project to encourage the voluntary recording of archaeological objects found by members of the public in England and Wales. Every year many thousands of objects are discovered, many of these by metal-detector users, but also by people while out walking, gardening or going about their daily work.

Poultice:
Soft moist, conservation material, applied with or without a carrier on a surface, to draw out dirt or residues through gentle moisture release and evaporation process. Like a face mask that draws dirt from the surface through an evaporation process.

Powdery (CGM/ stone):
Corrosion in the form of tiny loose particles.
Powdering:
•    The result of material degradation which causes an altered surface which is loose and particulate
•    Paint layer: loss of paint layer through loose or detaching paint, usually the result of insufficient quantity of binding medium in the paint as originally applied, or a breakdown in the binding medium as result of deterioration.

Preventive:
Implementing environmental measures to aid in the long-term care of materials e.g. climate control and pest management. See Preventative conservation.

Preventive conservation:
Area of conservation focused on researching the impact of and risk factors with the potential to accelerate object deterioration. These agents of deterioration include unsuitable environments, IPM, pollutants, light exposure, physical forces.  See Integrated Pest Management (IPM).

Priming:
Stabilising broken edges of ceramic and stone objects to prevent powdering and further breakage, and to create a barrier layer before applying conservation adhesives.

Puckering:
(Textiles) Localised wrinkling and distortion caused by uneven tension and gathering of fabric often around embroidery.

Radiocarbon dating:
Find out about radiocarbon dating.

Radiography:
Find out about radiography.

Raman spectroscopy:
A non-destructive analytical tool used to identify materials that uses laser to highlight a material's unique light spectrum. Find out more about Raman spectroscopy.

Reconstruction:
Reattaching broken fragments of objects together to make them whole again. Conservation adhesives and techniques are used for this process.

Recto:
The front of print/drawing/painting.

Red rot:
A powdery crumbly surface, specific to leather. Sometimes with a strong smell.

Relative humidity:
Relative humidity is the amount of water vapour held in the air as a percentage of what it would be holding if it were saturated. It is a ratio of water in a specific atmosphere. Relative humidity is affected by temperature changes. Warmer air can hold more water vapour than cooler air, so the relative humidity drops if the temperature rises, and no additional water is added. Conservators monitor and manage RH when trying to reach the optimum environmental conditions for materials.

Repair:
The act, task, or process of repairing an object. The repair may be an adhesive or consolidant, solder or rivet, patch, material support. If repair/adhesive weakens along a break-line, the join may widen and start to move.

Residue/ deposit (CGM):
Deposit of foreign matter on the surface. May be from original use.

Re-touching:
An interventive treatment referring to the use of paint, pigment or other medium to blend in losses to artefacts or artworks' surfaces. This could be infilling losses in an oil painting on canvas or covering the unsightly appearance of a fill on a marble statue.

Reversible:
Using materials and treatments that can be removed if necessary. Not making any permanent alterations to an object. Reversibility underpins contemporary conservation ethics.

Rot:
The product of organic decomposition, sometimes seen in brown, white, or red particles on the object.

Salts (ceramics/ glass/ stone):
White crystal deposit visible on surface. Can cause catastrophic damage to surface and object itself. Salts occur on porous ceramics and appear as white powdery deposits on unglazed surfaces or along cracks and craze lines in the glaze.

Scanning Electron Microscopy (SEM):
Find out about scanning electron microscopy (SEM).

Scientific Research (related to the British Museum):
Science is used both to help protect and preserve and to elucidate the collection by informing preventive and interventive conservation approaches and improving understanding of the collection and its cultural context.

Scratches:
Linear marks on the surface caused by sharp or hard implement, often damaging outer surface or surface decoration/coating revealing fresher material underneath. 

Shattered (textiles):
Extensive splitting and loss in very deteriorated and brittle textile, usually silk, resulting from chemical breakdown of the material.

Shrinkage:
Where material has decreased in size, leaving gap or opening between joins. In textiles can cause bag (excess of material) or creasing where differential shrinkage between two different materials are joined.

Silvering (paper):
Shiny or mirror-like discoloration in the shadow areas of a photographic image. Caused by the ageing of excess residual silver compounds.

Sizing/ resizing:
Sizing is a part of the papermaking process. It is the addition of an adhesive to provide the paper with greater strength. Sizing also imparts paper with qualities which control the 'bleeding' of inks. Sizing materials can be added to the paper pulp prior to forming a sheet of paper or added after the sheet has been formed. In aged or deteriorated papers, the size may have broken down, making the paper more vulnerable to mechanical damage. Where this has happened, conservators may consider a resizing treatment.

Soil:
A black or dark brown material typically consisting of a mixture of organic remains, clay, and rock particles, usually from excavation.

Solvents:
Chemicals used in conservation to clean, remove accretions/ adhesives, dilute adhesives to make them more workable, i,e. acetone or industrial alcohol, white spirit 

Splintering:
Thin sharp slivers of wood, bone, ivory broken away from main body, along the grain, and projecting. Often around edge of break or split. May be at risk of snagging or further loss.

Split: 
•    CGM: an opening or expansion in the material.
•    Organics (textiles, skin and leather, plant fibre and barkcloth): a break in the material, damage usually resulting from deterioration and loss of strength of the material, sometimes the result of force but may be gravity, often along fold lines. Little loss of material.
•    Organics (wood, ivory): along the grain or across the grain, usually result of the shrinking, drying, or from impact. Measurements of width and length of splits are useful to monitor change. Clean fresh or bright wood inside split may indicate more recent damage. Often not clean break edge but associated with splintering.

Squashed/ crushed:
Inward or downward deformation resulting from external forces, usually of 3D objects in softer materials, e.g. hats, baskets.

Stains:
•    Ceramics/glass: localised patches of soiling penetrated into the surface which cannot be brushed off. On unglazed surfaces this may be apparent as dark areas. Glazed surfaces and glass may acquire smears from handling.
•    Metals: localised patches of soiling penetrated into the surface which cannot be brushed off or a localised discolouration, often caused by splashes of liquid or by contact with an acidic material, such as an adhesive or ink.
•    Stone: a localised discolouration, often caused by environmental factors or structural materials used, splashes of liquid, such as an adhesive or ink.
•    Organics/paper: localised patches of soiling, penetrated into the surface, cannot be brushed off, often result of liquid or oils.

Stiffened/ hardened/ inflexible:
Hardening of material which was originally pliable and soft e.g. skins, leather, barkcloth.

Stripped:
Surface corrosion products have been removed by chemical solutions revealing the core or metal surface below.

Surface coating:
Transparent layer applied to the surface of an object. These can be waxes, natural or synthetic resins intended as protective surface.

Surface dust and dirt/ particulate dirt:
Loose dirt, dust, grime, soot, or another contaminant, lying on the surface, can be brushed off easily.

Tacky or sticky surface:
On plastics and rubbers may indicate severe deterioration of the material, may also be the result of previous coatings or adhesives used.

Tarnish:
Discolouration of a metal surface due to the formation of a thin film of oxide, sulphide or other corrosion product. Used most often to describe the dark corrosion that forms on silver.

Tatami:
Is a type of mat used as a flooring material in traditional Japanese-style rooms. Traditionally made of rice straw to form the core with a covering of woven soft rush (igusa) straw, tatami are made in standard sizes, with the length exactly twice the width, an aspect ratio of 2:1. Usually, on the long sides, they have edging (heri) of brocade or plain cloth, although some tatami have no edging. Tatamis are used as flooring in the Hirayama Studio for the conservation of Easter pictorial art on paper and silk. 

Tear:
A break in fabric, paper, other sheet, or woven materials because of tension or torsion. Usually begins at the edge of the object and often follows areas of weakness such as folds and other areas of physical damage. Tears are associated with little loss of material: tear edges meet but may be some fraying.

Tensile testing:
Strength testing of materials to examine how they may deteriorate.

Transfer print (ceramics/ glass):
Decoration applied onto ceramics, by transferring an engraved design from paper.

Undulations/ buckling/ wrinkling/ cockling:
Uneven deflection of a flat surface of usually 2D materials such as mats, textiles, barkcloth, canvas paintings, paper and vellum.

Unstable:
Object has sustained significant amounts of damage making its structure unstable or with extensive losses or breaks and is at risk of further damage.

Unsupported paint ledge:
Where gesso or material underneath paint layer is eroded away leaving jutting paint layer.

Warped/ bowed:
Concave or convex distortion of hard materials such as wood, bone, ivory, horn, often due to swelling and shrinkage of the material, but material not actually bent, cracked, or broken.

Water damage:
Typically impacts either or both physical and aesthetic properties of an object. For example, water damage can cause staining, and there may be associated dye bleeding, running or loss of paint surfaces, as well as accelerating the formation of tears, losses, and degradation within the object. 

Water stains (paper):
In paper objects water stains often induce an overall change of colour within areas that have been in contact with water. Another indication of water staining is the formation of a 'tide line', which is typically a darker line at the limit of the area exposed to water. 

Weakness:
Loss of strength in the object that leaves it frail, fragile, and liable to yield, break, or collapse under pressure or strain.

Wear:
Gradual deterioration of the object's surface by use or any continued process.

Worn:
Shows signs of wear/continuous use.

X-ray:
A form of electromagnetic radiation with very high frequency and energy. X-rays lie between ultraviolet radiation and gamma radiation on the electromagnetic spectrum. It is used to investigate the manufacture of an object, in particular sculpture, among other uses.

X-ray diffraction:
An analytical tool for identifying materials.
Find out more about X-ray diffraction.

X-Ray Fluorescence Spectrometry (XRF):
A non-destructive analytical tool for identifying materials.
Find out more about XRF.