[en] This paper shows how general productivity in the schematic Copular Construction for the verbs become (‘become’, developed from an original sense ‘arrive’) and wax (‘become’, from an original sense ‘grow’) abruptly followed when a pre-copular stage had reached a threshold value. It is argued that the presence of such a threshold itself, or the abrupt switch to general productivity rather than a gradual increase in productivity, results from the fact that the Copular Constructions featuring become and wax are not the end result of a single diachronic lineage of constructions, but that this switch has to be seen as the result of an interaction between lineages of constructions, which belong to two groups: (i) constructions involving a certain lexeme, which gradually change and interact with each other; (ii) constructions involving already existing copulas, notably weorðan ‘become’, which provided a template of general productivity upon which the newly emerging copulas could graft. The paper also contributes to the diachronic research on the largely ignored area of copulas denoting change of state, and in effect provides the first analysis of the development of become, which is surprising given its importance in the English language.