In this contribution, we explore the impact of Alnuset, an artefact of dynamic algebra, on the conceptualisation of the notion of algebraic equality. Many research works report about obstacles to conceptualise this notion due to interference of the previous arithmetic knowledge. New meanings need to be assigned to the equal sign and to letters used in algebraic expressions. Starting from the hypothesis that Alnuset can be effectively used to mediate the conceptual development necessary to master the algebraic equality notion, two experiments have been designed and implemented, one in Italy, the other in France. They are reported in the second part of the present paper.