This paper explores the metaphor of the classroom as a "crucible" for early professional learning where beginning teachers forge professional identities in complex, unpredictable, paradoxical, affectively and physically potent contexts of practice. It works into the dissonances and contradictions of the micro-narratives embedded in the accounts that three high-achieving early career English teacher graduates give of their early professional learning in schools. It traces the conflicts they experience in the gap between "economies of performance" and "ecologies of practice" within which they improvise new professional identities as teachers. Their effective "transmutations" into teachers are contingent on a bewildering range of factors, many of them out of their control. As the medieval transmutation of lead into gold was analogous to personal transformation, purification and perfection, so new teachers aspire to ideals of practice that may be impossible to achieve. The paper moves beyond simplistic conceptualisations of theory-practice binaries in new teachers' work and evaluates the impact of new pressures from globalised discourses of standardisation and professionalism that erase singularity, particularity and relationality. Rather, it posits professional learning as complex identity work that is variously constrained and enabled by local institutional factors and broader policy contexts that affect the capacity and desire of beginning teachers to introduce and sustain innovative pedagogies in their English classes.