CERTIFYING THE AUTHENTICITY OF A WORK OF ART
("Authentic: accredited as true and positive due to the characters, requirements or circumstances coinciding within")
Or in other words, making something true by ... PROVING IT. So simple, yet so often complicated depending on the state of conservation and, logically, the resources available to prove or disprove the authenticity of the work of art in front of you. It would take a long time here to describe all the experience accumulated over many years of research and work in this field. Without a doubt, what we can assure from experience is that if you have a real interest in authenticating a work of art, THERE ARE ONLY TWO WAYS:
A) Obtain the TECHNICAL and OBJECTIVE evidence that proves or disproves authenticity or authorship. These tests (remember, technical and objective) CERTIFY THE AUTHENTICITY OF THE WORK, and not what any Tom, Dick or Harry may say, with just one exception: come over one day to see Mr. Da Vinci, Renoir, Rembrandt, Goya and Picasso, amongst others, and let them personally tell you, "Yes my friend, I painted that on a Tuesday afternoon and I also remember that it was raining."
B) Get someone (a person, company or, best of all, a certain "market") to buy the piece because "it is obviously authentic".
Careful with the sale of art on the Internet, here's an example lasting just two minutes:
http://ib3tv.com/20130828_203168-la-guardia-civil-ha-detingut-un-home-de-47-anys-per-un-presumpte-delicte-destafa.html
In this laboratory, we just do option A, and even though sometimes it's the slowest option, it is definitely the safest. Here are some jobs carried out in THESE TESTS. The result is not always the desired one, but IT IS THE RESULT, not an opinion.