The importance of the alum trade in the Mediterranean and between the Mediterranean and North-Western Europe is, paradoxically, reflected in the small volumes mentioned in the documentation. Many Italians, including Florentines, were trading alum, hence the existence of documentary sources allowing for a qualitative analysis of this commodity’s trade. However, these documents are unable to provide a sound basis for a global assessment, nor can they reveal trends due to the paucity of preserved accounts.