There is no single method for dating glass or enamel. CIRAM laboratories combine several scientific analyses to reliably determine the age of your glass objects and enamels .
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The analysis of glass objects and enamels is based on three main axes: chemical composition, state of alteration and origin of alteration. These data can be used to help authenticate a work of art as part of an acquisition or museum appraisal.
At CIRAM, each part is studied using a combination of complementary laboratory techniques: optical microscopy, scanning electron microscopy (SEM), imagingetc. Each method reveals precise, cross-referenced information, interpreted by our specialized scientists.
The aim is to build up a coherent, documented body of evidence that will enable us to distinguish between an authentic, antique object and a modern production, or even a counterfeit.
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The chemical composition of glass reveals valuable information about its origin, period and manufacturing technique. Vitrifiers, fluxes, stabilizers or pigments: each component plays a role. A high concentration of lead or potassium, for example, enables an object to be dated back to the Middle Ages or the Renaissance. Pigments such as cadmium or chromium indicate modern production, dating from the 19ᵉ or 20ᵉ centuries.
Our scientists identify the constituent and chromogenic elements of glass to establish reliable dating. Our analyses, renowned for their accuracy, are used by numerous museums, auction houses, antique dealers and collectors in France and abroad.
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Analysis of weathering is a key stage in the study of ancient glass and enamel objects. Humidity, temperature variations and micro-organisms gradually degrade the material over the centuries. This alteration provides clues as to the age of the object.
Characteristic signs of natural ageing include deep weathering, alkali leaching, multi-layered structures (onion-skin type), micro-bubbly facies, silica gel and surface sediments.
Conversely, the presence of fluorine in weathered areas is indicative of modern, artificial weathering, often carried out to imitate the ageing of old glass.
Request a studyWhen the object's state of preservation allows, a microscopic sample is taken, so as not to alter the integrity of the piece. This sample is then embedded in epoxy resin to facilitate handling and cutting. A microsection, perpendicular to the surface, is then prepared for detailed analysis.
Thanks to microanalysisThis cross-section allows us to assess the depth of weathering penetration into the material. It also reveals the formation of multi-layered structures, responsible for the iridescence visible on the surface of old glass.
When the object is too fragile or precious to allow direct sampling, we prefer to use surface replicas. This non-invasive method involves applying a film of cellulose acetate to targeted areas of the object. After drying, this film is gently removed, taking with it the most superficial layers of the material as well as any deposits or alterations.
These replicas can then be examined using optical microscopy and scanning electron microscopy coupled with elemental analysis (SEM-EDX). The aim is to identify the nature of the alteration: natural, age-related or artificial. For example, the presence of fluorine may reveal modern chemical intervention.
In cases where no sampling, even microscopic, is possible - for example, on objects of great heritage value or in a perfect state of conservation - we resort to a totally non-invasive method: analysis using a PIXE probe with extracted beam.
This innovative technique enables the chemical composition of glass to be studied directly, without destructive contact, and in an ambient atmosphere. It offers precise quantification of the major, minor and trace elements present in the material.
These data make it possible to identify the raw materials used, evaluate the manufacturing conditions and better understand the technical processes employed at the time the object was created.
When you choose CIRAM, you benefit from more than 20 years of experience in scientific analysis of art objects and heritage objects. Our multidisciplinary team of physico-chemists and archaeologists offers analysis solutions tailored to the nature, state of conservation and value of your objects.
Thanks to our state-of-the-art equipment and rigorous methodology, we provide reliable, documented and usable answers for museums, curators, restorers, auction houses and collectors. Based in France, we operate worldwide to support the authentication, conservation and historical study of antique glass, medieval stained glass and art enamels.
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Contact our teamsNo, there is no absolute dating method for glass. However, CIRAM combines several physico-chemical analyses to reliably estimate the age of an object.
It provides information on the raw materials used, the manufacturing techniques, and helps identify any signs of modernity.
Yes, in some cases, surface replicas or in situ analyses can be carried out, particularly in listed buildings.
Depending on the complexity of the object and the method chosen, lead times vary from 2 to 6 weeks. A personalized estimate is drawn up beforehand.
Simply contact us via the online form. Our teams will guide you towards the most suitable analysis method for your object.
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