Part of Fondation Constant's mission is to protect the legacy of Constant Nieuwenhuys. The foundation is usually informed when works on the market are thought to be a copy, false or misattributed to Constant. Each situation has different implications.

  • First situation: Infringement on copyrights - an existing work of art is copied by someone, who, without prior permission of the copyright holder/Pictoright, reproduces the work and/or makes the work available to the public-with the artist’s name or his own name. This is considered a breach of or infringement on copyright and will therefore be handled by the organisation that handles the artist’s Intellectual Property rights.
  • Second situation: Misattribution - a work is mistakenly attributed to the artist. Even though there might not have been the intention to deceive, these works must be unveiled to avoid the illusion for owners or potential buyers that the work represents a certain value as if it were an authentic work from the artist.
  • Third situation: Forgery - a work of art is created with a deliberate intent to deceive. These works are usually presented falsely as a product of another time and/or artist. This could concern copies of existing works of the artist (falsification) or newly created works in the style of the artist as a consequence of which the work can be misattributed to the artist. Both situations are considered a forgery and a criminal act and will therefore be handled by the justice department and Pictoright.

The negative effects of these dealings have an impact both on individuals involved, the value of the works of the artist, and on the art market in general. Fondation Constant is supportive in the fight against these activities. We have close ties to both Pictoright, the Dutch Criminal Investigation Department for Art Related Crime and parties such as the Art Loss Register, who are all dedicated to eradicating  criminal activities from the art market.

On this page we will post information on the doubtful art works we encounter and where we have encountered them. To avoid law suits we will refrain from mentioning the specific parties involved.

NB: Fondation Constant does NOT give out certificates of authentication. When a work adheres to our guidelines for authenticity we will add it to out digital catalogue raisonné.

Tips when buying art

  • Ask for documentation on the work of art. Original works usually are obtainted through offical channels and come with invoices, catalogue/exhibition listings and are mentioned in art books.
  • Ask for a provenance. Original works are usually easily traced back to their source, this list of previous owners is called a provenance. Original works of art come with a provenance.
  • Do a background check on the seller. Is the seller a well respected art gallery that is well known for selling the art of this artist?
  • Do a google search on the prices. If the selling price seems too good to be true compared to works you find at the well renowned galleries, it probably is. However, above a certain price level most galleries do not make their prices public.
  • If a work is sold as assigned to... instead of by... it usually means there is reasonable doubt about the work's origin.
  • If buying online, check the Terms and Conditions of the online resellerThey might already indicate that they are not responsible of the authenticity of the works they offer!

These are some rules of thumb that should give you an indication of a works authenticity. If after this checklist, you still are unable to reach a conclusion, you can contact Fondation Constant for an assessment. Go to Assessment, for more information.

Fondation Constant is a not for profit organisation and your donations are always welcome and ever necessary: paypal.me/FondationConstantNL

Fondation Constant cannot be held responsible and/or liable for any damages, costs, expenses, loss or grievances incurred by publication or the use of the content published with regard to "Copyright Infringement, Misattribution and Forgery" on this website.
Fondation Constant will only publish information on such works if, after expert research with regard to the work, the case etc, Fondation Constant is of the opinion that such work is not authorised or authentic. However, these publications are to be considered the opinion of Fondation Constant only. Fondation Constant does not accept any liability for damages, costs, losses etc. arising from such publication.

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Title Year Technique Category CID
2025 Oil painting, ca 1949 No title/Figures with facial features 1949 Oil painting Forgery 7977
2025 Aquarel, ZT-Jeune garçon, 1991 No title-Head 1991 Watercolour Forgery 7985
2025 Aquarel, ZT-Samurai, 1994 No Title 1994 Watercolour Forgery 7986
2025 Oil painting, 1956, ZT-Stad ZT/Stad 1956 Oil painting Forgery 7998
2025 Oil painting, 1939 ZT-Figure with animals and ladders 1939 Oil painting Forgery 7999
1962 ca ZT-Sateliet No title/Satellite 1962 Drawing Forgery 7611
Schets naar Lijn zonder einde (vals), ca. 1962 Schets naar "Lijn zonder einde" 1962 Drawing Forgery 7614
2024 Paarden met maan, 1948, watercolour-MoArt Paarden met maan 1948 Watercolour Forgery 7927
2024 Gouache, New Babylon, 1969 Babylon 1969 Watercolour Forgery 8008
2024 No title-Birdlike figure No Title/Birdlike Figure 1949 Drawing Forgery 7953
2024 No title-Birdlike creature No Title/Birdlike Creature 1949 Drawing Misattribution 7954
2024 Drawing, year unknown Crayon drawing 1948 Drawing Misattribution 8000
2023 Oil on linen, 1949 No title/Three Figure with Bird 1949 Oil painting Forgery 7430
2023 Gouache, No title-Two fish, no year No title/Two Fish 1949 Watercolour Misattribution 8003
2023 Aquarel, 1997 Copy of Femme et enfant 1997 Watercolour Copyright Infringement 7438
2023 Terre Brulée, 1951 Rendition of Terre Brûlée in Yellow 1951 Oil painting Forgery 7337
2022, aquarel, No title-Twee figuren, 1991 No title/Two Figures 1991 Watercolour Forgery 8004
2021 Drawing, No title-Animalistic Figures, 1949 No title-Animalistic Figures 1949 Drawing Forgery 8005
2021 Watercolour, No title-Animal, human, bird, 1950 No title/Animal, Human, Bird 1950 Watercolour Forgery 8006
2021 Drawing, no year, signed Buffalo 1969 Drawing Misattribution 7338
2021 Drawing, No title, 1966 No title/Creature 1966 Drawing Misattribution 8007
2021 Watercolor, 1995, signed Copy of La belle noiseuse 1995 Watercolour Copyright Infringement 7339
2021 Photo Photo Constant and Boumibol 1951 Various Copyright Infringement 7341
2021 Gouache, 1948, signed No Title/Bird 1948 Watercolour Forgery 7342