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
2018 Washed Ink, signed Constant 1997 No Title/Not Sure What I'm Looking At 1997 Drawing Forgery 7365
2018 Moeder en kind, 1952 Copy of "Moeder en Kind" 1952 Watercolour Copyright Infringement 7364
2018 Mixed technique, no year No Title/Boat? 1980 Watercolour Forgery 7363
2018 Mixed technique on canvas, 1975 No Title/Blue Lanscape 1975 Oil painting Misattribution 7362
2018 Mixed technique on canvas, 1980 No Title/Purple Landscape 1980 Oil painting Misattribution 7361
2018 Mixed technique on panel, no date No Title/Brownish Landscape 1980 Oil painting Misattribution 7360
2018 Mixed technique on canvas, 1981 No Title/Greyish Landscape 1981 Oil painting Misattribution 7359
2018 Mixed technique on canvas, 1978 No Title/Lanschap Grey and Brown 1978 Oil painting Misattribution 7358
2016 Oil on canvas, no year No Title/A Lot of Oil Paint on Canvas 1980 Oil painting Forgery 7357
2020 Watercolor, 1997 Yet Another Copy of Femme et Enfant 1997 Watercolour Copyright Infringement 7356
2020 Watercolor II, 1997 The Umptheenth Copy of Femme et Enfant 1997 Watercolour Copyright Infringement 7355
2020 Tekening, 1945 No Title/Two Figures 1945 Drawing Forgery 7354
2020 Oil on linen, titled "Vogel", signed, 1949 Copy of Bird [I] 1949 Oil painting Copyright Infringement 7353
2020 Oil on linen, Kat, signed, 1949 Kat 1949 Oil painting Forgery 7352
2020 Oil on linen, titled "Kat", signed, 1949 Copy of Kat 1949 Oil painting Copyright Infringement 7351
2020 Watercolor, signed, 1997 Copy of La Mélancolique 1997 Watercolour Copyright Infringement 7350
2020 Oil on linen, signed, 1956 Copy of Grote Beer 1956 Oil painting Copyright Infringement 7349
2020 | 2013 Oil and sand on canvas, no year No Title/Lanschap Grey and Black 1980 Oil painting Misattribution 7348
2020 Gouache, 1950 Copy of "Man met fluit en poes" 1950 Watercolour Copyright Infringement 7347
2020 Mixed technique on paper, 1973 No Title/City on Hill 1973 Drawing Forgery 7346
2020 Drawing, signed Constant, no year Horse 1969 Drawing Misattribution 7345
2021 en 2002 drawing, no sign., no yr No Title/Man with Cigarette 1980 Drawing Forgery 7344
Drawing of Ambiance d'une ville future 1958 Watercolour Forgery 7343
2021 Gouache, 1948, signed No Title/Bird 1948 Watercolour Forgery 7342