The explosive triacetone triperoxide (TATP) is produced by the acid-catalyzed reaction of hydrogen peroxide and acetone, and methods for its identification are important in forensic and military scenarios. Previous work has documented concomitant crystalline polymorphism of the crude reaction product. Here, we have investigated the crystalline phases resulting from TATP syntheses from aqueous hydrogen peroxide as well as from sodium percarbonate and urea peroxide as oxidant sources, under different concentrations and types of acid. Powder X-ray diffraction (PXRD) patterns of the as-prepared powders indicate that, in contrast to previously published conditions, rapid precipitations afford a pure crystalline phase of TATP. High concentrations of Brønsted acid lead to the selective formation of a single kinetic crystalline phase, while a Lewis acid (SnCl4) gives rise to a pure specimen of the thermodynamic phase. Additionally, this study highlights the utility of PXRD as a rapid and high-confidence identification tool for TATP which has only now become feasible due to the fairly recent disclosure of crystal structures of the various TATP crystalline polymorphs.