By Charles Rose, founder of Glacier Art Objects
Authenticating fine art rests on three things: connoisseurship (does the work look right to an expert eye?), documentation (provenance, exhibition history, and a catalogue raisonné reference), and physical evidence (materials and pigment analysis). A signature alone is not proof, and a certificate of authenticity is only as reliable as the authority that issued it. Value is then set by the artist's market, the work's quality, condition, and provenance.
Authentication and valuation are two sides of the same coin: you can't sensibly value a piece without knowing what it is, and you can't fully establish what it is without considering the market for it. Both depend on evidence. Here is how the work actually gets done.
Table of contents
- The three pillars of authentication
- Are signatures proof of authenticity?
- Are certificates of authenticity reliable?
- The catalogue raisonné
- How to research provenance
- How to get art valued
- Frequently asked questions
The three pillars of authentication
A confident attribution rests on three lines of evidence:
1. Connoisseurship. Does the work look right? The handling of paint, the structure of a composition, the way an artist drew a hand — these are things specialists internalize over years of looking. Connoisseurship alone is rarely enough today, but it's where every authentication begins.
2. Documentation (provenance). A chain of ownership from the artist to the present, plus exhibition history, scholarly references, and inclusion in a catalogue raisonné. Every documented anchor point reduces uncertainty.
3. Physical evidence. Pigment analysis, X-ray, infrared reflectography, and other materials testing can disprove a forgery (period-incorrect materials) or support an attribution. Physical evidence rarely proves authorship alone, but it can disprove a false one definitively.
The strongest attributions combine all three.
Are signatures proof of authenticity?
No. A signature is one piece of evidence, not proof. Real artists' signatures vary across a career; forged signatures are easy to replicate; and many genuine works — sketches, studies, gifts to family — are unsigned. Many valuable prints by Dürer, Rembrandt, and Goya bear no signature at all, since pencil-signing wasn't conventional until the late 19th century. Treat a signature as supporting evidence, never as authentication on its own.
Are certificates of authenticity reliable?
Only when issued by a credible authority. Useful sources include the artist, the artist's estate or foundation, a recognized authentication board, a specialist on that artist, or a major auction house's catalogue entry. Less useful: a COA from the same seller offering the work, or from an unidentified "appraiser."
It's worth being blunt here. Insurance and appraisal professionals increasingly regard generic certificates of authenticity as weak evidence, precisely because they're so easy to fabricate — a quick search turns up tutorials on producing one. What carries real weight is provenance documentation and a catalogue raisonné reference, plus where the work was sold. Always verify the issuing authority; if the named expert is dead, retired, or doesn't authenticate that artist, the certificate is worthless.
The catalogue raisonné
A catalogue raisonné is the definitive scholarly record of an artist's complete known output, with dimensions, dates, provenance, and exhibition history for each work. For collectible artists it's the single most important reference. A work included in one carries significant weight; a work not included isn't necessarily fake, but the question — how did it escape scholarly attention? — must be answered.
How to research provenance
Provenance research is detective work. Useful sources include old labels on the back of paintings (galleries, exhibitions, framers), stamps and seals on the verso, auction archives, exhibition catalogues, estate and probate records, and photo archives. For 20th-century European art, a gap between roughly 1933 and 1945 raises questions about possible wartime looting — reputable sellers will have addressed this directly. For the buyer's side of this, see our guide to buying art online safely.
How to get art valued
A real valuation requires a credentialed appraiser — typically a member of the American Society of Appraisers (ASA), the Appraisers Association of America (AAA), or the International Society of Appraisers (ISA). Online "valuation" tools and casual dealer opinions are not appraisals. Choose an appraiser who specializes in your type of art and who is independent — not someone who also wants to buy the work, which is a conflict of interest.
There are three valuation standards: fair market value (for tax, donation, estate purposes), retail replacement value (for insurance — generally highest), and auction estimate (for consignment). A formal appraisal should include the appraiser's credentials, the standard used, comparable sales, condition notes, photographs, and a signed certificate, and should be updated every three to five years for insurance.
Value itself comes from the artist's current market, the quality of the work within their output, subject and image, condition, provenance, and exhibition history. Two pieces by the same artist can differ in price by 100x based on these factors.
Frequently asked questions
How do you authenticate a piece of art?
Art is authenticated through three lines of evidence: connoisseurship (expert visual judgment), documentation (provenance, exhibition history, and a catalogue raisonné reference), and physical evidence (pigment and materials analysis). The strongest attributions combine all three. A signature alone is not proof of authenticity.
Is a certificate of authenticity reliable?
Only when issued by a credible authority such as the artist, their estate, a recognized authentication board, or a major auction house. Generic certificates are easy to fabricate and carry little weight on their own. Provenance documentation and a catalogue raisonné reference are far stronger evidence.
What is a catalogue raisonné?
A catalogue raisonné is the definitive scholarly record of an artist's complete known works, listing dimensions, dates, provenance, and exhibition history for each. Inclusion in one strongly supports authenticity, and it is the single most important reference for collectible artists.
How do I get my art valued or appraised?
Hire a credentialed, independent appraiser who specializes in your type of art — ideally a member of the ASA, AAA, or ISA. Provide any provenance, receipts, and prior appraisals. The report should state the valuation standard used, comparable sales, condition, and photographs, and should be updated every three to five years for insurance.
Does a signature prove a painting is authentic?
No. Signatures vary across an artist's career, are easily forged, and are absent from many genuine works. A signature is supporting evidence only. Authentication depends on connoisseurship, provenance, a catalogue raisonné reference, and where relevant, materials analysis.
Charles Rose is the founder of Glacier Art Objects and Sand and Rose LLC. Over more than a decade in the trade, he has handled and sold over 18,000 works of fine art, antiques, jade, sculpture, and collectible objects.
Every piece in our gallery comes with the documentation we have — provenance, prior exhibitions, references — and an honest assessment of what remains uncertain. Get in touch about a specific work.