Introduction to Object ID
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Distinguishing Description

Distinguishing Features (by Henry Lie)

Does the object have any physical characteristics that could help to identify it (e.g., damage, repairs, or manufacturing defects)?
An object’s physical condition provides one of the best means of identifying it uniquely, particularly when it is one of a number manufactured to a common design or when it closely resembles other objects of the same kind. Distinguishing Features allows the recording of physical characteristics (e.g., scratches, creases, stains, drips in paint or glaze, bubbles, surface texture, etc.) that could help to uniquely identify an object. Such distinguishing features are typically small relative to the size of the object, and are usually the result of a chance event during the manufacturing process or minor damage sustained at a later date.

Recording Distinguishing Features
A combination of a narrative description, photographs, and sketches provides the best record of distinguishing features.

Narrative description has the advantage of requiring no special equipment, no photographic or artistic skills, and no need to add material, such as photographic prints, subsequent to the recording session. A written narrative can be incorporated into a database more easily than photographs or sketches. On the other hand, narrative descriptions are less precise than images, unless the recorder has highly developed descriptive skills. For this reason narrative text alone is not recommended to record a unique feature. Avoid one-word descriptions of condition such as good, fair, or poor that do not identify an object or provide evidence for accountability in the event of damage in transit, in storage, or when on loan for exhibition.

When photographing distinguishing features, take care to select highly visible features and to record them precisely. Sketches can complement the written description and photograph of a distinguishing feature by locating it on the object and giving an impression of its form and extent. While simple sketches of unique features may take a few moments to conceive and produce, they may provide essential distinguishing feature information clearly and precisely.

Selecting a Distinguishing Feature
The nature of the object usually dictates the type of feature that should be selected. Ideally, the features chosen should be large enough to see with the naked eye. Structural components or elements of design in surface decorations should not be chosen as distinguishing features, since they are more likely to be repeated in similar objects, copies, or examples from an edition. In addition to the critical quality of uniqueness, the durability of the selected feature is an important consideration, if the record is to be valid over a long period of time. Some features may be removed or obscured by accidental or intentional changes, such as cropping the edges from a paper object or a painting, varnishing a decorative surface, or polishing the surface of a metal object. Another consideration, in addition to the uniqueness and durability of features, is the relative ease with which they can be recorded and later recognized from the record made.

Works of Art on Paper
Typical distinguishing features for works of art on paper include tears, creases, abrasions, holes (losses), structural repairs, in-painting and other restorations, stains (present and removed), watermarks, edge patterns, cropping of edges, and the exact location and nature of collectors’ marks and watermarks. Consistency of paper quality and the uniform procedures used to print multiple editions can produce objects that are very difficult to differentiate. Because of the great similarity among many multiples, it is wise to select and record two features.

While paintings present fewer challenges than multiple editions, some painting styles lend themselves to the production of exact copies, which can be difficult to distinguish one from another. In such cases, even design elements may not record uniqueness. More useful features include crackling in the paint surface, distinctive brush strokes, damage or losses, repairs, irregularities at the edge of the canvas, and the pattern of paint at the periphery of the paint area. When the artist paints with a dynamic technique that results in a distinctive pattern of brushstrokes, the photographic details of design elements can constitute a reliable and easily located set of unique features. The reverse side of a painting can also provide an excellent and often overlooked source of information, such as signatures, inscriptions, stains, stamps, damages, or unique aspects of the fabric support. See Textiles below for further comments on fabric.

Both paintings and paper objects are vulnerable to being cut down in size, so recording only features located at the object’s edges is unwise. Similarly, because restorations are subject to change over time, they should not be used as the sole means of establishing a record. Moreover, restorations on many paintings are nearly invisible and can thus be difficult to record. The best distinguishing features are those occurring in areas least subject to loss or alteration.

Cast metal objects often belong to editions of multiples. As with prints on paper, care should be taken to select distinguishing features unique to an individual casting rather than to the model from which it is derived. Tool impressions made on the surface of the metal after casting can offer unique characteristics for recording purposes.

Casting flaws, such as air bubbles or larger voids in the metal, and the applied metal patches often used to repair them, offer suitable distinguishing features, as can chance patterns caused by the flow of metal during casting. Cast and non-cast metal objects have many features in common. Deep or highly visible scratches and abrasions, dents, and irregularities in welds or other types of mends or joins can all provide unique characteristics for recording purposes. However, it is important to remember that there is a danger of some recorded features being eradicated at a later date by polishing and reworking of the surface, painting and repatination, or application of protective coatings.

Glass and Ceramics
The highly uniform production methods for glass and ceramic objects can result in artifacts that are difficult to distinguish from one another. Chips, larger losses, cracks, glaze crack patterns, bubbles, scratches, abrasions, repair locations, and areas of irregular surface texture or coloration can be used to create records for accurate identification. When intentional features of the design are substantially irregular, these too can be used.

Wooden objects are often unique, and offer a wide variety of distinguishing features. In addition to many of the damage-related features mentioned above, wooden objects may often exhibit pronounced grain structure, irregularities in joinery, irregular details of incised or carved surface decorations, and saw-mark patterns. Details of decorative surface coatings and inlay work also provide unique characteristics appropriate for identification records, unless they happen to be highly uniform.

Machine-made and even hand-woven fabrics are often produced with great uniformity. Irregularities in the assembly of separate components may provide a degree of uniqueness in some cases. Losses, tears, wear patterns, irregularities in the weave or fiber, repairs, stains, and the irregular application of colorants are the most likely features for selection for this purpose. These features apply as well to the backs of paintings on canvas.

Recording the location of the distinguishing feature
The location of the distinguishing feature selected should always be recorded. Annotating the location of the distinguishing feature on an overall photograph is the preferred technique of recording its location, or by adding the information to the written description or sketch of the object. As with the descriptions of the features, the more concise and precise the location description, the more useful it is likely to be.

Note on security
In the case of well-known works of art of high value, the existence of documented distinguishing features should not be made public knowledge, either before or after a theft. Descriptions and photographs of these features provide the owner/custodian and police with information not known to individuals who may claim to possess the object in an attempt to obtain a ransom under false pretenses. Any individual can claim to have an object, and may be able to provide dimensions and a description of its subject matter from published sources. Only the person in possession of it will be able to answer questions such as "What can you see on the top left hand corner of the rear of the canvas?"

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