How do you determine the age of a stone artwork?
Without a doubt, determine the real age of a stone sculpture or artifact is a genuine challenge! Stone artifacts can be reproduced in a later period and older stone and material could also be used to reproduce artworks from an earlier period. But one important aspect that cannot be replicated – not by technology or power tools – is the natural process of “weathering.”Weathering takes time and over time every stone artwork naturally weathers. Weathering can take place slowly or quickly affecting the surface workmanship of an artwork and creating visible changes to it’s surface such as aggradations, degradation, swelling and shrinkage. These surface changes can be observed on a weathered stone artwork , especially in and near the sculptor’s incisings or grooves that he leaves on a stone object . These changes may be caused by the type of hard or soft stone selected , by under- ground burial environmental conditions , by above- ground surface climate exposure, or by the manner in which the artwork may have been ceremonially and physically handled by man during it’s life. For example, under dry and cool burial conditions weathering effects are minimized. Humid conditions and nearby external mineral deposits under ground on the other hand can intensify weathering of a burial object and cause greater surface encrustation. Some old stone artwork may be ceremonially encrusted with old ochre or adorned with natural pigments….leaving traces and clues of it’s past life.
A stone objects natural weathering is quite different than by weathering that is chemically simulated.
By examining the stone’s surface and incisings carefully for naturally caused surface deposits, patina, and crispness (or lack of from non traditional carving tools) – combined with the passage of time, we can determine with some degree of certainty if the artwork is genuinely old or not. This then is a good beginning step at tracing back its age and an assessment on authenticity can be begun to be performed with reasonable confidence.
Material scientists can carefully examine evidence of natural weathering and combine this assessment with other methods of evaluation such as style and material comparison with known artworks in museums and private collections from dependable sources or they can analyze “tool signatures” (markings left by man when the object was transformed) and by examining surface encrustation material under magnification – the real age of a stone artwork can be inferred with reasonable accuracy and a reliable dating procedure can be performed to attribute an item to a given culture and era.
We are passionate about stone art.
We have been collecting, buying, and selling old stone aratwork for many years now. We pride ourselves on our ability to select genuinely old and authentic artworks that offer you good collector value: a combination of authenticity, quality, and fair price. We hope you have enjoyed this information and look forward to serving you and helping you add some fine stone artwork to your collection…if not now…than hopefully in the future.
Thermoluminescence (TL) Testing:
Thermoluminescence or TL testing is a scientific method of determining the age of a particular ceramic by establishing when it was last fired. When clay is fired, the electrons of the atoms are thrown off their nucleus. Over a period of time, the electrons gradually reattach themselves. Using sophisticated equipment and procedures, TL testers can determine how many electrons have reattached themselves and, as a result, determine the age of the ceramic.
Where the ceramic is soft enough – say, in the case of earthenware or low fired stoneware – a sample of grains from the artifact is taken by drilling a small hole in its body. A hole measuring 1/8 inch (approx 3mm) diameter x 1/4 inch (approx 6mm) depth will usually supply enough material for a test. In the case of high fired stoneware or porcelain, a diamond drill is used to take plugs from the body. Usually, two plugs measuring 1/4 inch (approx 6mm) diameter x 1/4 inch (approx 6mm) depth will be sufficient.
Most earthenware can be tested, although some early white-colored pottery does not yield reliable results.
Most stoneware and porcelain can be tested. However, some pieces are potted in such a way that the drilling of the plugs required for testing is either not possible or would essentially ruin the piece, for example in the case of a thinly potted bowl.
Here are two reputable laboratories which can undertake TL testing;
- The Oxford Authentication Laboratory in Oxfordshire, England
- Kotalla Laboratory, Haigerloch, Germany
The Kotalla Laboratory is the world’s oldest private laboratory specializing in TL testing and charge about $260 per piece for testing plus about $60 for drilling one piece. Their representative is based in New York City. The Oxford Authentication Laboratory charges about $400 per piece for testing earthenware and low fired stoneware, and $500 per piece for testing high fired stoneware and porcelain. The cost for drilling the test sample by an Oxford representative in New York is $85 for the first sample and $35 for each subsequent sample. Drilling for stoneware will range from $100 to $125 if the piece is sent to a specialist elsewhere in the US. In both cases, any and all shipping costs must be borne by the purchaser. Including shipping fees, a test for earthenware or low fired stoneware is likely to cost in the region of $300-$500, and more for high fired stoneware or porcelain.
You should contact them well ahead of your need to determine their schedules and turn around time.
We carefully choose and evaluate each work of art guaranteeing you quality design, authenticity, and your complete satisfaction,
Schneible Fine Arts LLC guarantees the origin, quality, and authenticity of all works of art that we offer. Read more below about our approach, findings, and tips on how you can better appreciate the beauty these fine objects represent.