If you have a work of art that is signed with the name Constant and you would like confirmation of its authenticity you can submit the work for research by Fondation Constant. When we research a work for an authentication we do publish the results on our website. In case of an authentic work it will be part of the catalogue raisonné [WORK] and in case of an infringement of copyright, misattribution or forgery we will post it on the page Doubtful Origin.
NB: We do not afford economic valuations of work by Constant. In addition Fondation Constant does NOT give out certificates of authentication.



Oral assesment
After receiving the application form, photo’s and documentation, a telephone call or meeting for the oral assessment will be scheduled. An oral assessment is free of charge. NB: this assessment does not include extensive research nor any written statements and/or oral statements to third parties!

Written statement
After receiving the application Fondation Constant sends an invoice. When the payment is received, an appointment is scheduled to inspect the object first hand (if possible). In the meantime research is conducted on the documentation and the provenance. When the research is concluded and three experts have separately reached their conclusions a written statement will be issued. If the work is deemed an original by Constant a certificate of documentation is provided and the object will be added to the catalogue raisonné.

€200,- Written statement about authentication
Price exclude 21% VAT & banktransfer costs

Criteria for including a work in the Constant Catalogue Raisonné
For a work to be included in the CCR as an authentic work by Constant (1920-2005) it must meet one or all of the conditions below:
1. The work appears in Constant’s archives:

  • As an archive entry
  • As an ektachrome
  • As a photo

2. The work appears in valid documentation:

  • The work appears in books published by Constant himself.
  • The work appears in catalogues of exhibitions, set up with Constant’s knowledge and/or co-operation.
  • The work appears on invitations to exhibitions, set up with Constant’s knowledge and/or co-operation.
  • The work appears on sales and/or price lists and invoices in Constant archive.

3. The provenance of the work is legit:

  • The work has a proven and reliable and documented history leading back to Constant.

If you have any questions you can address them to

NB: When we’re busy it can take up to 3 to 4 weeks to handle an authentication.

Fondation Constant is a not for profit organisation and your donations are always welcome and ever necessary:


Fondation Constant