This chapter, in dialogue with the energy humanities task of thinking transition, attempts to undo cement by assessing material transformation in the cement kiln. Portland cement, a bulk commodity that has been a critical building material in the concrete mix throughout the 20th century (along to gravel, sand and water, all of which are now recognized scarce), is seen as problematic, even destructive, in times of climate emergency because the production process in industrial cement plants itself contributes significantly to global carbon emissions. As key sites of Anthropocene metabolism, the global web of kilns become object and narrative device of architectural and environmental histories, and indeed the humanities to address and expose modern tropes of growth and progress. From an elemental perspective the kiln burns not only fossil fuels, and today so-called alternative fuels; the chemical process itself, as known through patent history, relies on the fact that half of the carbon dioxide is released during the calcination process. Since the emissions come from the raw meal itself, it is argued, any solar project, social, ecological, and economic, as well as cultural would have to rethink the kiln, since innovation in admixtures and fuels only prolong the existing cement regime.