MinMax presents an approach for reusable formwork for thin-shell, double-sided, highly detailed building envelopes based on binder jet 3D printing technology and Glass Fiber Reinforced Concrete (GFRC). GFRC is about 75% lighter than traditional concrete with rebar, and its life cycle is longer than traditional concrete, making it a great candidate for freeform thin shell facade elements. Using binder jetting reusable formwork outperforms the milled and 3D printed thermoplastic formwork in terms of speed and cost of fabrication. We could demonstrate this approach on a minimal surface structure assembled from 32 GFRC elements, cast with 4 individual formwork elements, each of them reused 8 times in less than 4 days. By demonstrating that 3DP formwork cannot only be used once but also for small series production, we increase the field of economic application of binder jetting for formwork. The presented fabrication method of formwork based on additive manufacturing opens the door to more individualized, freeform architecture using GFRC.