Most of the tests that can be carried out to distinguish archaeological pieces from recent copies are surprisingly simple and accessible also to the layman.

Ceramic articles have been preserved only because they were protected by the earth in which they were buried for centuries. The humidity in the soil, rich in minerals and plant roots, penetrates the ceramic body. These extensive traces left by the earth offer the surest and simplest means of establishing authenticity.
 

The first test should therefore consist of moistening a clean part of the surface with a wet finger or brush (1). If the object is authentic it will give off a smell similar to that of warm earth after a summer rain.

Petrified traces of roots offer a further clue (2). The roots which cling to the porous ceramic body leave their minerals behind in the form of crystalline deposits on the surface. A natural encrustation can be discerned by the semicircular petrified root bed (drawing a) left by the decomposed root.

Through a normal 10X magnifying glass, which every antique buyer should have with him, these round beds are clearly distinguishable. Forgers try to imitate these marks with applications made of glue, earth and cement on the surface.
 

Encrustations, if authentic, are sufficient proof that an archaeological item is authentic. Chemically speaking, these crystals are mostly calcium carbonate (CaCO3), a compound of calcium and carbonic acid. A very simple test  demonstrates the authenticity of encrustations: it is sufficient to sprinkle a few drops of hydrochloric acid, a substance to be found in many households. First the surface forms blisters which continue until the material dissolves completely. Unequivocal evidence is provided by a spectroscopic analysis of the encrustations, which a well-equipped laboratory can carry out in a few minutes.

An absolutely certain indication of authenticity is provided by carbonized mould fungi, which develop on edible burial gifts. These fungi expand radially in an irregular way (4). In the course of centuries a micro-organism (Micrococcus carbo) converts the fungus material into carbon. Under a magnifying glass they appear as a crystalline mass, whilst the black stains forgers like to make by spraying black paint on the surface show up as round, smooth-surfaced spots. There is no point in spraying a genuine item with industrial paint: the presence of artificial marks alone is therefore enough to classify the object as a fake.

A further testimony to authenticity is provided by the inside of a vessel which remained for a long time full of water or mud underground. The various levels reached by the water have left rings (5). The inside of faked vases are generally rinsed with a uniform brown or grey mixture of earth and cement or glue which assumes a uniform colour and structure on drying (6).

Not all authentic archaeological finds bear readily visible signs of age. The dry ground of South America, southern Italy and China may produce encrustations which can only be detected with a good microscope.
Antique objects found at the bottom of the sea are not covered in earth crystals but only in the fossil remains of marine animals which are not fakable.

Restoration

Almost all terracotta vases are found as potsherds in excavations.
The edges of old cracks in excavated pottery have been smoothed by time and corrosion (7). Sharp-edged cracks point to recent damage and therefore a fake object (8).

Fakes
 

Fake excavated pottery and 19th century copies thereof also give themselves away because the objects are often bigger and more beautiful than the originals.
 

Typical of a fake is this urn of a handsome young Etruscan, whose vigorous and healthy appearance is an idealized representation. (9)

Particularly big, beautifully decorated glass objects in a perfect state of preservation are suspect. They were used only rarely in graves. Simple bottles, on the other hand were mass-produced in industrially organized workshops and placed in thousands in tombs.

The ablest copyists of antique glass today are in the Middle East, particularly in Israel, Syria and Jordan. But these fakers do not have the time to meticulously imitate the signs of age produced by wear, corrosion and deposits which, if examined by an expert, will always reveal their true nature.

Excavated Chinese pottery

Much of the inhabited area of China is covered in porous loess, which produces scant mineral deposits on the pottery surface. Nevertheless authentic figures generally have characteristics which, if examined at least under a microscope, can permit a reliable distinction between recent and antique items.
 

In the fertile loess live many insects and worms which leave petrified traces. (10 - 12)

Visible traces of earth, not noticeable on the painted and glazed areas, must instead be expected in the unprotected areas of the porous ceramic surface, such as on the face and in the interior of a figure (11).

(11)

Much appreciated are figures of horsemen (13) and about 80 percent of all those objects declared authentic are fakes. But also for authentic objects most of them are made up of potsherds which have been reassembled and overpainted.

(13)

In general, excavated objects from all parts of the world present the same characteristics which can be recognized and interpreted in the same way as indicated for Mediterranean excavated pottery and the best evidence is provided by petrified traces of roots.

The ceramics of a number of ancient cultures were painted in smooth, bright colours and patterns conforming to European tastes. Modern acrylic paints used on recent copies tend to achieve a similar optical effect to the genuine colours.
But if a small inconspicuous area is heated with a hot-air gun or over a gas flame the difference is quickly noted: at 300° acrylic colours blister or darken. Acrylic colours dissolve slowly in alcohol. If a piece of cotton wool soaked in alcohol is left in contact with the paint for an hour, it will wrinkle and can be wiped off (14).
The presence of petrified roots as well as other crystalline deposits on the surface is similar to those on European excavated objects.

Glass wares served as receptacles for food and drink to be consumed in the next life. The carbonized remains of these organic substances are generally visible through the transparent parts of the glass (15).

These marks, which range in colour from brown to black, are a good indication of authenticity. The distribution of the marks is important however, as their position must correspond to the upright or horizontal position in which the container was found in the tomb.

Pottery, and terracotta in particular, are porous materials which absorb large quantities of mineral-rich groundwater. Glass, on the other hand, has an impermeable surface which minerals can penetrate only slowly and in small quantities, forming thin layers.

An absolutely reliable and inimitable characteristic of an authentic encrustation on glass is that over time, at the slightest vibration, paper-thin flakes fall away, accumulating at the bottom of the receptacle (16).

Iridescent antique glass surfaces are particularly prized (17). A favourite way of imitating iridescence on glass is to use gelatin made from bones or fish scales, into which an iridescent powder has been mixed. This is dissolved by a drop of hot water

Subject:  EXCAVATED BRONZES 
Total pages: 8  Illustrations: 20 -  Chapter  Authentic encrustrations

Subject: EXCAVATED GLASS 
Total pages: 4  Illustrations: 9 - Chapter Mediterranean glass

Subject: CENTRAL AND SOUTH AMERICAN POTTERY 
 Total pages: 4  Illustrations: 11  - Copies and Fakes

The Founders and staff
of the Museo d’Arte e Scienza

Gottfried Matthaes
Founder and  President

Giovanna Cozzi Matthaes
Co-founder

Dott. Chim. Peter Matthaes
Lab. Director and CTU

www.copiesandfakesinart.com