A professional condition report is the single document that should govern any bid, yet it is written in guarded house language that rarely spells out real risk. Learning how to authenticate a painting begins here, not in a laboratory, but with the ability to read a condition report clause by clause and translate restrained wording into an honest picture of a work's state. This guide decodes the terms a collector meets most often: craquelure, relining, overpainting, retouching, losses, foxing and fading, and it sets out what an ultraviolet image can and cannot reveal. It is written for the experienced collector who already knows the market and wants the mechanics laid out plainly. Authentication is never a single verdict; it is the convergence of provenance, attribution and condition evidence, and the report is where the condition half of that case is made or lost.
Key takeaways
- A condition report is advisory evidence, not a guarantee of authenticity; the buyer, not the house, carries the authenticity risk, and the International Council of Museums (ICOM) Code of Ethics for Museums frames conservation as work that must be documented and reversible.
- The Art Loss Register lists more than 700,000 stolen, looted and disputed items and runs more than 400,000 market checks a year for over 130 subscribing houses, a title screen no condition report replaces.
- Longwave ultraviolet light at 365 nm exposes overpaint, retouching and later varnish, but it confirms surface history, not attribution (Art-Test).
- The Swiss Fine Art Expert Institute estimated in 2014 that up to 50% of circulating works were misattributed or forged, a figure still debated (Artnet News).
- Every conservation procedure should be documented and reversible, so a well restored work recorded in full is not a compromised one (ICOM Code of Ethics for Museums).
What a Professional Condition Report Actually Contains
Knowing how to read a condition report starts with knowing its parts. A condition report is a structured statement, at LLB Auction a three-page document, describing a work's physical state at a fixed moment: its support, its paint and media layers, its surface coating, and any past intervention. It is not a valuation and not a certificate of authenticity. The ICOM Code of Ethics for Museums sets the standard the trade borrows: every conservation procedure should be documented and reversible, and any added material should remain identifiable from the original. A report written to that standard tells you what was done, where, and how much, which is one part of learning how to authenticate a painting rather than merely admiring it.
Read the document in the order a conservator examines the object. First the support: canvas, panel, paper or board, and whether it is original. Then the ground and paint layers, where losses, cracking and flaking live. Then the surface, meaning varnish, dirt and any coating. Finally the frame and any labels, stamps or inscriptions on the reverse, which carry provenance rather than condition. A report that moves through those layers in sequence is easier to trust than one offering a single sentence of reassurance.
The report should also record the examination method: normal light, raking light, ultraviolet, and occasionally infrared or X-ray. When a house states a conclusion but omits the method, treat the omission as information. The reading skill this article builds sits alongside the wider process set out in Provenance, Attribution and Condition: the Due Diligence Behind Every Lot. Condition is one leg of a three-legged case; the others are provenance and attribution.
Craquelure, Relining and the Structural Notes That Matter
The structural notes decide whether a painting is stable or a conservation project in disguise. Craquelure is the network of fine cracks that forms as paint and varnish shrink with age. An even, overall craquelure is normal and often reassuring on an older oil; irregular patterns, a bullseye radiating from a point of impact, or lifting edges signal past damage or unstable layers, according to conservation glossaries such as Stella Art Conservation. The pattern, not the mere presence of cracks, is the diagnostic.
Lining is the attachment of a new fabric to the back of an original canvas to reinforce it. Relining means the canvas has been lined more than once. The distinction matters: early wax-resin linings can darken the paint film and stiffen the canvas as they age, so a relined work may read differently in person than in a photograph. A lining is not a defect; an undisclosed or failing lining is.
Watch also for cupping (paint curling at the crack edges), cleavage (paint separating from the ground), tenting and active flaking. Each is a warning that the paint film is losing its grip on the support. A work described as stable should show none of these in active form.
| Report term | What it usually means | What to weigh |
|---|---|---|
| Overall in good condition | Age-appropriate wear, no significant damage or restoration | The floor, not praise |
| Stable | Not actively deteriorating now | Says nothing about past restoration |
| Craquelure consistent with age | Natural crack network from ageing | Reassurance, provided the pattern is even |
| Lined or relined | Canvas reinforced once, or more than once | Ask when, and with what material |
| Minor restoration | Retouching confined to small losses | Request the percentage and a UV map |
| Extensively restored | Significant intervention across the surface | A value and originality question |
Overpainting, Retouching and Losses: Reading the Restoration
Restoration language is where reports are most guarded, and where how to authenticate a painting most often turns. Retouching (also called inpainting) is new paint applied only within the boundaries of a loss, to reintegrate a damaged area. Overpainting is paint that extends beyond the damage, over sound original paint, often to hide a repair or alter an image. Retouching within a small loss is routine and acceptable; extensive overpainting changes how much of what you see is by the artist's hand. Simon Dickinson's condition guidance draws the line plainly: retouching replaces what is missing, while strengthening means original paint is present but abraded.
Losses are areas where the paint or ground is gone. A report should give their number, size and location: a 2 mm loss in an open sky is trivial, the same loss across a signature or a face is not. Scattered small losses at the edges are age; a concentrated loss in a focal passage is a value question.
The percentage of the surface that has been retouched is the number to extract. The market and museum practice treat a work with limited, documented retouching very differently from one where overpaint covers a quarter of the picture. When a report gives no percentage and no map, ask for both before you bid. This is the same discipline the attribution question demands, set out in the attribution ladder from autograph to follower of.
Foxing, Fading and the Condition of Works on Paper
Works on paper follow different rules, and two terms dominate their reports: foxing and fading. Foxing is the reddish-brown or yellowish spotting that appears on paper through localised chemical change, linked to trace metals such as iron and copper and to mould, per the American Institute for Conservation's Conservation Wiki. In a stable, low-light, low-humidity environment foxing is arrested rather than reversed, so a report should state whether the spotting is active or historic.
Fading is the loss of colour from cumulative light exposure, and it is irreversible. The Northeast Document Conservation Center (NEDCC) states that light damage accumulates with intensity and duration, so a work displayed for decades under bright light carries losses no restorer can recover. Conservators measure exposure in lux (one lux equals the light of a single candle falling on one square metre from one metre) and track it in lux-hours over time. A pastel or watercolour described as fresh, with strong colour, has usually been protected.
Read paper reports for support condition too: tears, creases, cockling, tape stains, trimming and old hinges. A sheet trimmed to the platemark has lost margin and value; acidic backing or tape leaves stains that migrate into the sheet. Because paper reveals its history so openly, a candid paper report is often more informative than a painting's. For what the reverse of any work discloses, see how to read the verso, the back of the painting.
How to Authenticate a Painting With UV and Raking-Light Images
Learning how to authenticate a painting from images means learning what each light actually shows. Ultraviolet (UV) examination uses longwave light, typically 365 nm, to make surface materials fluoresce differently. Natural resin varnish glows a soft green-yellow; later synthetic coatings, retouching and overpaint appear as darker patches, because modern materials fluoresce differently from aged ones, as imaging specialists such as Art-Test describe. A dark passage under UV is not proof of deceit; it may be documented conservation. What UV gives you is a map of where the surface has been touched.
Two cautions apply. A masking varnish laid over retouching can suppress those dark patches and produce a falsely clean UV image, a trick condition guides flag directly. And UV reads only the surface: it says nothing about the layers beneath, which is why houses add infrared or X-ray for deeper questions.
Raking light, a beam skimmed across the surface at a low angle, reveals topography: impasto, canvas weave, planar distortion, lifting paint and the ridges of old repairs. It shows texture where UV shows chemistry. Read together, the two images corroborate the written notes, yet neither authenticates a work on its own. The International Foundation for Art Research (IFAR), founded in 1969, stresses that its own authentication opinions are advisory and rest on convergent evidence, not a single test. Imaging supports the case; it does not close it.
Decoding the Restrained Language of the Report
House language is deliberately restrained, and the collector's task is translation. A report will rarely call a work damaged; it will call the condition commensurate with age. The words carry graded meaning, and these seven translate most reliably.
- Overall in good condition. The baseline for age-appropriate wear with no significant damage or restoration. Read it as a floor, not praise.
- Stable. The structure is not actively deteriorating now; it is not a claim about past restoration.
- Minor restoration. Retouching confined to small losses. Ask for the percentage and a UV map.
- Restored or extensively restored. Significant intervention. Treat it as a value and originality question, not a red flag by itself.
- Relined or lined. Structural reinforcement of the canvas. Ask when it was done and with what material.
- Surface dirt or discoloured varnish. Cosmetic and usually reversible by cleaning, at a cost.
- Craquelure consistent with age. Reassurance that the cracking is natural, not impact damage.
The rule behind the vocabulary is liability. Under the discipline the ICOM code encodes, a house that authenticates or overstates condition becomes liable, so reports understate and the buyer must read up, not down. When a phrase is vague, the honest move is to request additional photographs and clarification, which reputable houses provide. Silence in a report is rarely neutral; the missing sentence is often the answer.
How to Authenticate a Painting Before You Bid: A Worked Reading
To see how to authenticate a painting in practice, trace one report from front to back. Consider a mid-career contemporary oil on canvas, offered online, with a three-page report. Page one records the support: original canvas, unlined, minor corner draws. That is good structural news and closes the relining question.
Page two covers paint and surface: an even craquelure consistent with age, two 3 mm losses in the lower background, retouching estimated at under 3% and confined to those losses, confirmed by a UV image showing two small dark points against an even green-yellow varnish fluorescence. Read together, that is a lightly restored, largely autograph surface.
Page three records provenance and the reverse: a gallery label, an inventory number and a clean check against the Art Loss Register, which lists more than 700,000 items and runs more than 400,000 market searches a year for over 130 subscribing houses. Now cross-read the attribution: does the catalogue raisonné, the scholarly inventory of an artist's accepted works maintained through catalogue raisonné scholarship and databases such as IFAR's, record this work or its dimensions. When condition, provenance and attribution agree, the case is strong. Had page two shown 30% overpaint beneath a masking varnish, the same procedure would have told you to walk away. Convergence is the method; no single line is the verdict.
FAQ: Condition Reports and Authentication
These are the questions collectors raise most often about how to authenticate a painting from the evidence a condition report and its images provide.
How to authenticate a painting without sending it to a lab?
Read the condition report against the provenance and the attribution, and look for agreement. Study the UV and raking-light images for undisclosed retouching, check the reverse for labels and stamps, and screen the title against the Art Loss Register. Laboratory analysis settles deeper questions, but a disciplined reading of the report and the images resolves most works before a bid, and tells you when specialist testing is worth the cost.
What does a condition report not tell you?
A condition report describes physical state, not authorship or value. It will not confirm that a work is by the named artist, will not price it, and will not carry the authenticity risk, which stays with the buyer. It also reflects one moment in time. Use it alongside provenance research, a catalogue raisonné check and, where stakes are high, independent scientific analysis.
Is a restored painting worth less than an untouched one?
Not automatically. Limited, well documented restoration is normal and often expected on older works, and the ICOM standard treats a recorded, reversible intervention as sound practice. Value falls when restoration is extensive, undisclosed, or amateur, particularly overpaint across a focal passage. The decisive figures are the percentage of surface retouched and whether the work has been relined.
How do you recognize a forged signature on a painting?
A signature sitting on top of the varnish, fluorescing differently under UV, or applied over craquelure rather than under it, is a warning that it was added later. Compare the letterforms and medium against documented examples in the catalogue raisonné. A signature alone never authenticates a work; it is one signal read alongside condition, provenance and attribution.
Does a clean condition report guarantee authenticity?
No. A clean report confirms good physical state, not authorship. The Swiss Fine Art Expert Institute estimated in 2014 that up to 50% of circulating works were misattributed or forged, and condition has no bearing on that question. Authenticity rests on provenance, attribution scholarship and, when needed, scientific testing, with the condition report supporting the case rather than settling it.
How LLB Auction Clears the Threshold Before You Bid
LLB Auction is a contemporary art auction house built on rejection: roughly 40% of submitted works are turned away at intake, so what remains has already cleared a threshold. Three practices support how a collector reads condition here.
Due diligence on every lot. Each consignment is checked for certificate, ownership history and conservation record, and screened against stolen-art databases before it reaches a sale. The house documents evidence and never claims certainty on its behalf.
A three-page condition report on each work. Every lot carries a structured report covering support, paint, surface and reverse, written to be read rather than to reassure. The house never describes condition as better than the report states.
Transparent, asynchronous sales. Four timed online auctions run in 2026 on the house's own platform, each lasting 7 to 14 days, with the buyer's premium fixed at 20% and no hidden costs. The Contemporary Art Spring 2026 sale offered 25 lots and sold 23, for roughly €39,480 in gross hammer.
LLB Auction positions itself as the buyer's advocate, the party that cleared the threshold first, and it never bears the authenticity risk the buyer carries. To follow new sales and receive condition reports as lots are catalogued, register at llb-auction.com and join the collector newsletter.
Conclusion
A condition report rewards the collector who reads it as evidence, not reassurance. Craquelure patterns, the lining and relining history, the retouching percentage, foxing and fading on paper, and the UV and raking-light images together compose an honest account of a work's state, provided you translate the restrained language and treat every silence as a question. The document is advisory, the buyer carries the risk, and no single line is a verdict.
Ultimately, how to authenticate a painting is not a test you pass but a case you build: condition, provenance and attribution converging until the picture holds together. Read the report clause by clause, ask for the percentage and the map, cross-check the reverse and the catalogue raisonné, and let the evidence, not the wording, decide the bid.
Sources
Further reading
- Provenance, Attribution and Condition: the Due Diligence Behind Every Lot
- The Attribution Ladder: Autograph, Attributed To, Studio Of, Circle Of, Follower Of
- Certificate of Authenticity or Catalogue Raisonné: Which Proof Counts
- The Back of the Painting: How to Read the Verso
References
- Art Loss Register, About Us : Art Loss Register, 2026
- IFAR Home and Provenance Guide : International Foundation for Art Research, 2017
- ICOM Code of Ethics for Museums : International Council of Museums, 2017
- Protection from Light Damage : Northeast Document Conservation Center, 2024
- Foxing : AIC Conservation Wiki, 2024
- Over 50 Percent of Art is Fake : Artnet News, 2014
- Terminology Used in Art Condition Reports : Stella Art Conservation, 2024
- How to read a condition report : Simon Dickinson, 2021
- Reflected Ultraviolet Imaging for Examination of Artworks : Art-Test, 2023