Metals

Test the quality and properties of metals, such as particle size or elemental composition, down to the smallest detail. You will find practical case studies here on customized instruments for metallurgy and other applications that demand non-destructive methods for metals analysis.

Metals

Application notes

Using X-ray technology in the preservation of cultural assets

Historical objects stand as testimony to our cultural past. They speak of personalities, of nations – indeed, of humanity. The most important task in saving cultural assets is preserving this heritage. To do so, these pieces of art and everyday items must be carefully examined and researched.

Every culture has its traditions, its rituals and its artistic epochs. Just from the way objects are designed, historians can read a lot about the people who originally used them. Frequently, the material composition is characteristic of a specific time period or region. Thus, accurate material analysis can make it possible to distinguish originals from counterfeits or to detect parts that were added later.

So as not to damage these often delicate and valuable objects, the examination method must be as gentle as possible. Non-destructive X-ray fluorescence analysis is therefore ideal for use on cultural assets.

Since it was designed as a flexible handheld instrument, Fischer's XAN 500 X-ray fluorescence instrument is convenient to use outside a laboratory. Despite its small size, it is nonetheless equipped with the full-fledged WinFTM® software. Plus, fundamental parameter analysis allows unknown alloys to be inspected for their components without prior calibration.

The handheld XAN 500 makes it possible to measure bulky and odd-shaped parts right where they stand, for example in museums or at excavation sites. (Photo: Esther Hoyer)Fig.1: The handheld XAN 500 makes it possible to measure bulky and odd-shaped parts right where they stand, for example in museums or at excavation sites. (Photo: Esther Hoyer)

The XAN 500 was tested at the GRASSI Museum of Applied Arts in Leipzig to examine an eagle lectern. The piece presumably dates from the 12th or 13th century and was made in Italy. Because the lectern consists of several parts bearing different stylistic elements, the restorer suspected that not all these elements were original.

Measuring on a lectern with a single column: All parts are made of brass. The small differences in the composition are probably due to inconsistencies in production.Fig. 2: Measuring on a lectern with a single column: All parts are made of brass. The small differences in the composition are probably due to inconsistencies in production.

Alloy analysis with the XAN 500 showed that the piece was made of tombak, a high-quality brass with a high copper content. All parts showed comparable concentrations of copper, zinc and lead – a strong indication that all pars were original. In addition, traces of nickel, tin, iron and antimony were found in the alloy.

X-ray fluorescence analysis based on the fundamental parameter method makes it possible to detect all the different components of an alloy. In this way, conservators can choose the correct materials to restore cultural assets as faithfully as possible, in order to preserve them for future generations.

Analysis of the alloy elements in antique coins

When researching the origin of antique coins, scientists use a variety of information sources. The smelting process or the ores used in minting for example contain information about the origin or the age of the coin. However, one needs to find ways to retrieve this information out of these often precious and rare coins without damaging them. But because coin alloys always contain both light and heavy elements, to gain meaningful results the researchers need a determination method that covers a wide range of elements and employs an efficient measurement routine.

A suitable way of learning more about the smelting process or the ores used in minting is x-ray fluorescence analysis (XRF). One of the biggest advantages of XRF is its non-destructive principle, keeping the sample intact while still allowing to analyse the composition at discretionary positions.

As an example, we analysed the composition of a Roman coin from 355 AD bearing the likeness of Constantine II. The results of a measurement using the FISCHERSCOPE® X-RAY XUV® are shown in Table 1: 13 elements are present in the alloy, including very light ones such as aluminium and silicon as well as heavy ones such as silver and lead.

Fig.1: Roman coin made in Constantinople in approximately 355 AD; found in Saarland in 2005. The rectangle marks the analysed area.

The evaluation software WinFTM®, with which all FISCHERSCOPE® X-RAY instruments are equipped, includes a very powerful routine that automatically employs multiple excitation conditions (x-ray tube voltage or primary filter), enabling optimal simultaneous detection of both light and heavy elements on any given sample – in one measurement step.

Element

content [%]

Element

content [%]

Al

2.52 ± 0.06

Fe

0.16 ± 0.01

Si

3.16 ± 0.06

Ag

0.94 ± 0.04

P

0.25 ± 0.01

Sn

0.80 ± 0.03

S

0.18 ± 0.02

As

0.09 ± 0.02

Cl

7.37 ± 0.12

Pb

3.54 ± 0.05

K

0.37 ± 0.01

Cu

79.90 ± 0.27

Ca

0.91 ± 0.01

   

Tab.1: Results of a repeat measurement in the eye of the head. By using a small collimator size the XRF determination allows the analysis of just the eye on the coin, where 13 different elements were found. Cu is the dominating element, but light ones like Al or Si show a similar concentration as a heavy one like Pb.

In antiquity, coins were minted almost exclusively from metals and alloys like gold, electrum, silver, billon, potin and brass/orichalcum. If the alloy components and trace elements of a coin can be accurately determined, one can draw conclusions about its origin and age.

The powerful x-ray fluorescence measurement system FISCHERSCOPE® X-RAY XUV® is tailor-made for the analysis of alloys containing a broad spec-trum of elements. Together with the sophisticated evaluation software WinFTM®, it provides ideal conditions for such non-standard and challenging measurement tasks as determining the composition of antique coins. For further information please contact your local FISCHER representative.

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