Objects can be continuously printed from a vat of photocurable resin at rates exceeding 430 millimeters per hour, thanks to a new approach to rapid and large-scale stereolithographic 3d printing (SLA). The method overcomes the challenges imposed by heat buildup from curing resin, which has limited the capabilities of previous iterations of continuous SLA 3d printing. Stereolithographic printing is a widely used method in commercial 3d printing. It relies on UV light to harden photoreactive resins into complex 3d shapes. A variation of SLA called CLIP allows for continuous photopolymerization of an object as it's pulled from the resin by introducing an oxygen permeable "dead-layer" where resin cannot cure, thus preventing adhesion between the emerging print and the UV interface at the bottom of the vat. However, the rapid polymerization of resin generates a lot of heat, and without adequate cooling, temperatures can quickly exceed the smoke point of the resin. Here, David Walker and colleagues present HARP, an approach free of the "dead-layer" that uses a flowing layer of fluorinated oil as a liquid-interface between the resin and UV interface. According to Walker et al., the flowing oil can be used as a heat exchanger to remove excess heat to maintain appropriate operational temperatures. What's more, the method is compatible with a wider range of resins, such as those normally reactive to oxygen. The authors demonstrate HARP's capabilities by printing objects in hard plastics, ceramics and elastomers.