Diagnosing or determining parameters for an installation for detecting open defects in the surfaces of parts by sweating

A method of diagnosing or determining parameters for an installation for detecting open defects in the surfaces of parts by sweating, the method comprising:

• providing at least one standard testpiece having a surface possessing at least one pattern having known geometrical characteristics representative of the type of defect that is to be detected;
• passing the testpiece through the installation to perform the steps of applying to the surface of the testpiece a penetrating composition including an indicator substance, washing the surface of the testpiece, drying, and applying to the surface of the testpiece a composition including a second developer;
• and illuminating the surface of the testpiece to illuminate the remaining indicator substance so as to form a developed image of the at least one pattern and deduce therefrom an indication about the quality of the operation of the installation by comparing the developed image with said known geometrical characteristics,
• wherein, prior to passing through the installation, the standard testpiece is subjected to cleaning treatment comprising the steps of:
• immersing the testpiece in a bath containing an emulsifier with the surface of the testpiece being inclined relative to a horizontal plane;
• carrying out a first rinsing under pressure drying;
• applying a first developer at the location of the at least one pattern;
• and carrying out a second rinse under pressure, in order to eliminate from the at least one pattern any residue of indicator substance accumulated from a previous use of the testpiece, prior to passing the testpiece through the installation for diagnosing or determining parameters for the installation.