Infrared spectroscopy is not a new technique, nor a recent discovery. What is new is its application to determine the age and authenticity of artworks. This method has been used for decades, worldwide, by all major chemical and pharmaceutical companies, employing thousands of instruments with the same programs and equipment as the laboratory of the Museum of Art and Science in the field of art. Thanks to its high reliability, precision, and ease of use, this analytical method has become one of the most important tools across many scientific sectors.
All materials on Earth, including those used to create works of art, are composed of specific sets of molecules.
Some of these molecules undergo measurable changes over time.
The infrared (IR) spectrum of a specific material shows its molecular structure as peaks and valleys (figs. 1, 2).
Signs of aging — such as oxidation, dehydration, and other alteration processes — cause a reduction in absorption peaks and, in some cases, their shift (fig. 3).
This dating method therefore allows two different types of spectrum evaluation, each capable of providing reliable results on its own.
The subsequent discovery of absorption frequency shifts in spectroscopic analysis has dramatically improved precision to an unexpectedly high level during the first years of application.
This accuracy, and the low influence of climatic factors (especially for wood not exposed to surface conditions), may be attributed to biological programs within the cell nucleus of the tree.
The remarkable precision of such biological programs is well known and evident during the wood’s growth phase.
Why the aging process of wood may also be “programmed” remains an open question for future cellular research.
The application of spectroscopic analysis for dating organic materials is patented
(Italian Patent No. 01266808 – G. Matthaes, 1993).
The evaluation and use of scientific methods are influenced by local laws and customs.
In Italy, where the Museum is based, the highest authority against art forgery is the Guardia di Finanza.
In its June 2007 publication on authenticity verification in art, the Museum of Art and Science’s laboratory is presented as a key reference, with six pages dedicated to explaining its spectroscopic dating methods for paintings, furniture, ivory objects, and more.
The probative value of the spectroscopic dating method is crucial in civil and criminal proceedings regarding the authenticity and age of artworks.
The spectroscopic method for wood dating is recognized by scientific bodies, restorer associations, and increasingly by major museums worldwide.
Over 15 years, the laboratory has carried out more than 20,000 dating analyses — both for research and for third parties — consistently confirming the method’s validity or contributing to its refinement.
Research into this new method began in 1990 because existing techniques (C14 and dendrochronology) had intrinsic limitations that made them unreliable for dating the roughly 1,000 antique wooden objects in the Matthaes Foundation collection, later donated to the Museum of Art and Science.
Collectors of furniture, panel paintings, musical instruments, and extra-European art still face similar challenges today.
Validation of the new method.
After three years of initial research (1991–1994) and the creation of frequency-based age calculation tables, the laboratory reached out to major international museums (1994–1995) to verify the method’s accuracy.
Six museums provided two categories of wooden samples:
(A) Known-age samples for calibration, and
(B) Unknown samples for blind testing.
The spectroscopic dating results allowed museums to evaluate the precision of the method — which proved to be both highly accurate and reliable.
The findings were later published.
The application of spectroscopic analysis for dating organic materials is patented (Italian Patent No. 01266808 – G. Matthaes, 1993)
Per molti metodi scientifici sono necessari campioni del materiale da esaminare. Generalmente i campioni richiesti sono minimi, di pochi milligrammi e la lacuna ha dimensioni inferiori a quelle dei danni provocati dai tarli, dalla corrosione o da altre cause accidentali.
Questi danni “naturali” sono spesso considerati una prova di antichità, mentre il prelievo di campioni per l’accertamento dell’autenticità di oggetti d’arte viene visto come un intervento contro la cultura. Le valutazioni opposte ovviamente non si basano su considerazioni culturali.
Questo dubbio è normale. Ma il legno è un materiale organico molto complesso di cui è nota la straordinaria resistenza all’acqua e al calore. L’indipendenza dagli agenti atmosferici di una parte della massa lignea è provata, tra l’altro, dall’ambra e da navi millenarie trovate sul fondo del mare. L’ambra è una resina che, pur essendo rimasta per più di 200 milioni di anni nei fondali sottomarini, nel letto di fiumi o nella terra umida, ha un aspetto molto simile alla resina fresca. Anche le travi di antiche navi hanno mantenuto la forma e l’aspetto di legno vecchio.
Dalla misurazione e dal confronto di spettri di materiale vecchio e giovane preso dagli esempi citati è risultato che esistono molecole del legno il cui comportamento è del tutto indipendente da fattori dell’ambiente esterno. Queste molecole vengono usate per la datazione spettroscopica.