The authenticity of a painting is established through:

Attribution (identifying the author, age, and authenticity) — a comprehensive study that includes three major stages:

Scientific and Technical (Laboratory) Examination
This is the most important and objective stage. It includes methods that allow determining:
- Chemical composition of paints
  - X-ray fluorescence spectroscopy (XRF)
  - Infrared spectroscopy (FTIR)
  - Gas chromatography–mass spectrometry (GC-MS)
  What it reveals: It allows determining which pigments were used. For example:
  - Titanium white appeared only in the 20th century.
  - Lead white was used until the 19th century.
  - Chrome green — since the 19th century.
  If a painting is claimed to be from the 16th century but contains a pigment from the 1920s, it is a forgery.
- Analysis of ground layers and binders
  Includes examination of:
  - type of ground
  - oils (linseed/walnut)
  - resins
  - organic substances
  This helps determine the era and sometimes the region.
- Dendrochronology (for wooden panels)
  For panel paintings: comparison of tree-ring patterns with dated reference tables. It can determine:
  - when the tree was cut
  - whether the date corresponds to the period in which the artist could have worked
  Example: if the panel was cut in 1650, the painting cannot be from the 15th century.
- Carbon dating (C14)
  Used for canvas, wood, and organic grounds.
- X-ray imaging
  Reveals:
  - underlayers
  - corrections
  - changes in composition (pentimenti)
  - hidden images
  Authentic old paintings often contain pentimenti — natural changes made during the creative process.
- Infrared reflectography (IRR)
  Reveals:
  - underdrawings
  - the artist’s original sketch
  - characteristic linework
  Each master has a recognisable “hand”.
- Ultraviolet fluorescence (UV)
  Shows:
  - restorations
  - later interventions
  - new varnish layers
Art Historical (Stylistic) Expertise
Conducted by independent specialists in a specific era or artist. They evaluate:
- painting technique
- composition
- brushstroke
- line quality
- comparison with authenticated works
It is important that the expert is highly specialized (for example, Italian Renaissance).
Documentary and Historical Expertise (Provenance)
The weakest but still important part. It includes the study of:
- ownership history (provenance)
- archives
- catalogues raisonné
- mentions in museums or exhibitions
- old receipts/photos
If a proven ownership chain exists from the 18th–19th century, the value increases significantly.
Final Authentication Report
A reputable laboratory provides:
- a technical report
- an art expert’s conclusion
- provenance analysis
- dating
- confirmation or rejection of authenticity