New method for dating copper and bronze artefacts

Date:

Share post:

How can the age of archeological objects be determined if the well-established carbon dating method does not apply, for example for metal objects? Spanish and Portuguese scientists have now introduced a technique for dating artifacts made of copper and bronze. Presented in the journal Angewandte Chemie, their electroanalytical method is based on the voltammetry of microparticles. It compares various corrosion products that form over long periods of time and works with only a few nanograms of material so it causes almost no damage.

New method for dating copper and bronze artefacts
Voltammetry of microparticles used to date archeological artefacts 
made of copper and bronze [Credit: © Wiley-VCH]

Voltammetric experiments produce current–voltage curves that have characteristic shapes for many compounds. In order to date copper-containing, archaeological finds, a team led by Antonio Doménech-Carbó at the University of Valencia examined the ratios of two different copper oxides, tenorite and cuprite, that can be differentiated and quantified based on their voltammetric curves.

When they are exposed to air, copper surfaces become covered by a natural layer of cuprite (Cu2O). Over time, this layer is slowly converted to other products of corrosion. As copper-containing objects age in a slightly corrosive environment, without contact with soils or sea air, a layer of tenorite (CuO) continuously forms over the primary cuprite patina. This occurs because cuprite reacts with oxygen from the air to preferentially form tenorite in an atmosphere containing CO2 or in the presence of calcareous materials. Examination of copper coins by scanning electron microscopy coupled with X-ray spectroscopy confirmed the presence of cuprite and tenorite.

To carry out the electroanalytical experiments, the researchers impregnate a graphite bar electrode with paraffin and dab the surface of the artifact with it. A few nanograms of the sample surface stick to the electrode, which is then dipped into an aqueous electrolyte. This causes almost no damage to the object. Copper oxide microparticles result in very characteristic peaks in the resulting current–voltage curves.

Of particular interest to the researchers is the ratio of the current peaks for tenorite and cuprite. It shows a steady increase with increasing corrosion time, as demonstrated with a series of antique coins from various collections, including the Prehistory Museums of València and Xàtiva (Spain), as well as the artificial ageing of Euro cent coins made of copper. The researchers were able to use the coins to establish a calibration curve that can be used to date objects of unknown age.

The voltammetric dating of a water pitcher from the Caliphal period and a Montefortino helmet from the Roman age gave ages of 1050±80 and 2150±150 years, respectively, which agree well with dates previously established from the archaeological context.

Source: Angewandte Chemie [July 11, 2014]

2 COMMENTS

ADVERTISEMENT

spot_img

Related articles

Remains of Native American village hailed a significant find

It now appears a special state review panel will be ready to vote sometime in March on whether...

Human deforestation outweighs climate change for coral reefs

Better land use is the key to preventing further damage to the world's coral reefs, according to a...

Deciphering compact galaxies in the young universe

A group of researchers using the Suprime-Cam instrument on the Subaru Telescope has discovered about 80 young galaxies...

Study finds earliest evidence in fossil record for right-handedness

Perhaps the bias against left-handers dates back much further than we thought. By examining striations on teeth of...

Prehistoric henge unearthed in Kent

An “incredible” prehistoric henge has been unearthed during an archeological dig in Sittingbourne. The Bronze Age find at...

Powerful mathematical model greatly improves predictions for species facing climate change

UCLA life scientists and colleagues have produced the most comprehensive mathematical model ever devised to track the health...

Ancient Maya developed super highways network more than 1,000 years ago

El Mirador is a late Maya preclassic city, located in Guatemala, in the heart of the Petén jungle,...

Norway fishermen post record-breaking whale haul

Fishermen in Norway have caught 729 whales this year, the highest number since it resumed the controversial practice...