The RTI Technique is one of the most advanced non-invasive multispectral diagnostics and allows the surface morphology of any kind of artefact to be studied, providing fundamental information hidden from visible light. The procedure involves the application of photographic methods to characterise the surface. This information is translated into a digital composite image that describes, for each pixel, the chromaticity and surface morphology of the subject under investigation. The acquisition offers numerous advantages in terms of accuracy and versatility. In fact, the real innovative strength of the RTI diagnostic survey lies in its ability to scientifically and unequivocally document the colour and true three-dimensional morphology of surfaces in a single, easy-to-read document. Mnemosyne has applied RTI to a large number of artefacts including a page of the Gutenberg Bible (B42) with very interesting and satisfying results.