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
2016 Mixed techniques on paper, 1940 No Title/Carrying Figure 1940 Drawing Forgery 7389
2016 Gouache on paper| Le vieux clochard, 1994. Copy of Vieux Clochard 1994 Watercolour Copyright Infringement 7388
2016 Gouache on paper, 1960 The Umpth Copy of "Interieur met laddertjes" 1960 Watercolour Copyright Infringement 7387
2016 Ink on paper III Owl 1969 Drawing Misattribution 7386
2016 Gouache on paper, 1969 Yet Another Rendition of Figuren in ruimte 1969 Watercolour Forgery 7385
2016 Ink on paper, no year II Stork 1969 Drawing Misattribution 7384
2016 Ink on paper, no year I Duck 1969 Drawing Misattribution 7383
2016 Watercolor and ink on paper, 1952 No Title/Figures on Plate 1952 Watercolour Forgery 7382
2016 Watercolor on paper, 1948 No Title/Ink Drawing 1948 Watercolour 7381
2016 Oil on linnen, 1949 No Title/Cityscape 1949 Oil painting Forgery 7380
2016 Oil on ..., 1958 No Title/Abstract Black White Red Yellow Mess 1958 Oil painting Forgery 7379
2016 Watercolor on paper, no year Watercolor Copy of "Interieur met laddertjes" 1969 Watercolour Copyright Infringement 7378
2016 Drawing on paper, no year No Title/Four Creatures 1949 Drawing Forgery 7377
2016 Oil on canvas, no yr, signed No Title/Abstract Yellow Red 1980 Oil painting Forgery 7376
2016 Oil on canvas, no yr, signed No Title/Abstract Blue Red 1980 Oil painting Forgery 7375
2016 Oil on canvas, no yr, signed No Title/Abstract Green Black 1980 Oil painting Forgery 7374
2016 Oil on canvas, no yr, signed No Title/Figure with Black 1980 Oil painting Forgery 7373
2017 Oil on canvas, 1960 No Title/Oil Paint Thickly Applied 1960 Oil painting Forgery 7372
2017 Lithograph, no yr, signed No Title/Pennz Oil 1980 Graphic Work Forgery 7371
No Title/Something Black on Blue 1999 Watercolour Forgery 7370
2017 Gouache on paper, 1960 Another Pretty Bad Copy of "Interieur met laddertjes" 1960 Watercolour Copyright Infringement 7369
2017 Watercolor, no year No Title/Shapes 1980 Watercolour Misattribution 7368
2017 Gouache on paper, year unknown No Title/My Kid Can Do This (Can It Though?) 1949 Watercolour Forgery 7367
2017 Collage, 1959 No Title/Abstract Yellow Blue Red 1959 Collage Forgery 7366