The « Mordançage » technique is a chemical modification of a classic B&W baryta paper print. It comes from a formula by Mr Marriage who gave this recipe in 1948 for a printing process using fatty inks by the effect of swelling the gelatine in the dark areas. This formula was modified in the 70s by Denis Brihat and JP Sudre to arrive at its current use. A mixture of cupric chloride, hydrogen peroxide and acetic acid ‘nibbles’ at the blacks in the image, ignoring the light areas and leaving a black border between these two areas to give the impression of engraving. This delicate process allows you to work in the thickness of the paper and to play on the areas where the gelatine has disappeared (the blacks thus become white and matt) and on the shine in the areas where the gelatine has been retained (shiny whites and light greys).