Ibn Sina (d. 1037) famously denied the veracity of alchemy. He denied alchemy beause he denied the ability of human beings to transmutate one species into another through natural means. Considering the stature of Ibn Sina, as well as the incisiveness of his argument, proponents of alchemy were bound to respond, and they did in a number of directions. Some alchemists, like Abu al-Qasim al-‘Iraqi (fl. 13th cent.), would sidestep Ibn Sina’s objections by claiming that all metals were a single species, thus effectively removing transmutation from alchemy. Other alchemists, like Aydemir al-Jildaki (fl. mid-14th cent.), would respond by transforming what kind of practice alchemy was, shifting the focus from a material technology to a temporal technology. While earlier alchemists tried to understand and manipulate the powers and potentialities that lie within the earth and within (the structure of) matter, post-Avicennan alchemy could become a technological vehicle for controlled acceleration, for localized time contraction. They respected Ibn Sina’s dictum that human beings could not transmutate on their own, due to the impossibility of knowing the differentiae (fasl) which define one species against another, but then turned their attention to transmutations that were already naturally in progress. Acceleration thus replaced fabrication as the primary alchemical function. Alchemists would claim to do what nature normally does, whether it be growing gold or gestating a fetus, only much, much faster. This paper will argue that the alchemists’ goal of outstripping nature was considered to be fundamentally predicated on the ability to quicken time within their flasks and stills, both by the alchemists themselves and their critics. Thus we can appreciate in later Islamicate alchemy the beginning of a now familiar trope in science and technology studies: the difference between the natural and the artificial and thus the border of nature.