Will Technical Analysis Authenticate my Painting?

There are numerous types of technical analysis for items of cultural heritage, used by academic institutions, museums, and highly funded laboratories.  This equipment is costly, and getting technical analysis done a particularly complicated process when you are an individual with no affiliation with an institution.  People who watch shows like Fake or Fortune sometimes get caught up in the thrill of wondering if the painting that they inherited from their great grandmother is actually a long lost Rembrandt.  However, as you will see below, spending money on technical analysis will generally not result in an authentication.  Technical analysis is done on items of cultural heritage primarily for research and educational purposes, for example, to learn how a particular artist worked, and what materials they used.  The following is a list of some common methods of technical analysis used in cultural heritage sectors, what they are primarily used for, and their limitations when it comes to authentications.

Carbon-14 / Radiocarbon Dating:  This method of technical analysis method provides age estimates for carbon-based materials that originated from living organisms.  This means only organic components can be dated with this method – bone, leather, wood, natural textiles, etc.  You cannot carbon date minerals, metals, or items made from non-carbon based materials.  The method is destructive – meaning a sample must be provided, and that sample gets incinerated during the process.  While this process is great for items that are many thousands of years old, its accuracy is limited for items from recent history.   In the 2003 movie Timeline starring Gerard Butler and Paul Walker, there’s a scene at the beginning of the movie where the characters are on an archaeological dig site, and they get excited about finding an artifact.  One of the characters asks “Did you carbon-date the ink??” The scientist on site responds “Of course I carbon-dated the ink! Look!” And then, the computer screen flashes the very specific year of 1361.  In reality, aside from the fact that carbon dating the ink would have required removing a large enough sample of the ink from the artifact to be visible (just under 1 gram), when you get an item carbon dated, the resulting analysis would look something like this:

1100-1200 – 5%

1200-1300 – 25%

1300-1400 – 46%

1400-1500 – 21%

1500-1600 – 3%

This report shows that the item tested has the highest probability that it came from the 14th century.  At the same time it also shows that there is 54% chance it came from a century other than the 14th century.  As you can see, carbon dating cannot give you a specific date, and even the century it suggests is not 100% definitive.  Additionally, carbon dating gives you an idea of when the living organism died, meaning if you carbon date the wood panel from a panel painting, you will get a rough century of when the tree was cut down, not the date when the painting was executed – though less common, the possibility exists that the artist used really old wood when the panel was prepared to paint.  At best, carbon-14 dating can give you a rough century of when your painting was likely made, but that’s as specific as it gets.  A knowledgeable art historian would be able to give you a better idea of the time period of your work, based on material composition and style.

X-Ray Fluorescence (XRF)    This type of analysis identifies elements in the sample it is analyzing, and is a non-destructive method, meaning you do not have to take a sample off of the artwork to perform the analysis.  It is currently available in “point and shoot” instrument (as in, point the instrument at a specific spot on your painting and get a reading of the elements present in that small spot), and also in a mapping-type device, which will give you a visual readout of an entire artwork with a breakdown of all the elements present throughout the work.  Pigments which make up the colours in paints are composed of all kinds of different minerals and sometimes organic dyes.  For example, vermillion red is made of mercuric sulfide, so if an XRF instrument takes a reading of red on a painting and it identifies mercury, then it is likely vermillion, a pigment that has been used by humans since the 8th century.  Students of technical art history learn which pigments were discovered/invented and made available to artists in which year.  So if the XRF takes a reading of red on a painting and it identifies cadmium instead of mercury, that would automatically indicate the painting was made in the 20th century, because that’s when cadmium red was invented and made available to artists.  Getting a complete reading of pigments present in your painting will not authenticate the work to a specific artist, all it can do is verify that it is congruous with artwork created in a particular time period.  Just because a painting contains the same colours/pigments that Rembrandt used, does not make that painting a Rembrandt.  XRF is used for the study of artist’s palettes, and also for identification of forgeries due to the presence of modern pigments.  XRF can de-authenticate a work (prove it to be false), but it cannot authenticate a work (prove it to be by a particular artist).

Fourier-transform Infrared Spectroscopy (FTIR)   This method is destructive in the sense that you need to get a sample from the artwork to put in the machine for analysis, though that sample does not get destroyed during analysis.  The FTIR instrument identifies materials by exposing the sample to infrared radiation, which then creates spectra to be able to match to a library of known spectra.  This is most often used with organic and polymeric materials, and can be used to identify whether a canvas is cotton, linen, hemp, or jute, if your paint binder is oil (linseed, walnut, poppyseed), gum arabic, egg tempera, or casein, or if that red pigment that was inconclusive with XRF is actually a dye-based pigment like carmine lake.  While this is fascinating technology, there are less expensive ways of identifying many of these types of things (like microscopy, solubility spot tests, and even microfade testing), and just like XRF, this cannot be used to authenticate an artwork or attribute it to a particular artist.  FTIR is primarily used for the identification of unknown materials.

Polarized Light Microscopy (PLM)   Many pigments can be identified using PLM based on appearance, and the shape of their crystalline structures.  PLM is also used to look at cross-sections of paint layers, which can teach us about an artist’s working technique.  Again, due to requiring a sample from the artwork, this is a destructive analysis method. Like the above mentioned techniques, identifying pigments cannot attribute a painting to a particular artist, though again, it could potentially prove that a particular artist did not paint a particular piece.

X-ray, Infrared, and Ultraviolet Imaging  These imaging techniques are non-destructive, and are very common practice in museums. X-rays and infrared images can sometimes show us if an artist made slight changes to his composition during his working process, or if another painting exists under the one we see, like in the case of this Picasso at the AGO.  Infrared images can show underdrawings made with charcoal hidden beneath the paint layers, and X-rays are blocked by heavy metals, often showing portions of the composition painted with pigments such as lead white.  These are necessary when a team of curators and conservators are considering doing a major intervention, like removing hundreds of years worth of retouches and overpaint, which would permanently change the look of an artwork.  There have been famous examples in museums of a conservation team discovering completely different compositions hidden beneath paint layers, and then making the choice to uncover those older compositions, like in the instance of this Vermeer. Ultraviolet light causes differential fluorescence of pigments and different types of resins.  UV light can also disclose areas of previous restorations or later additions to the painting.  Learning to identify resins and pigments based on their fluorescence takes much study.   Sometimes infrared or ultraviolet imaging can improve the readability of faded inscriptions or signatures.  These types of analyses can provide clues that can work towards the authentication of an artwork, but they are not definitive on their own.

The Art Conservatory does not do appraisals or authentications on artworks.  If you are looking for an appraisal, please visit the website of the International Society of Appraisers to find a qualified specialist in your area. https://www.isa-appraisers.ca/