The physical simulation of CAD models is usually performed using the finite elements method (FEM). If the input CAD model has one dimension that is significantly smaller than its other dimensions, it is possible to perform the physical simulation using thin shells only. While thin shells offer an enormous speed-up in any simulation, the conversion of an arbitrary CAD model into a thin shell representation is extremely difficult due to its non-uniqueness and its dependence on the simulation method used afterwards. The current state-of-the-art algorithms in conversion voxelize the input geometry and remove voxels based on matched, predefined local neighborhood configurations until only one layer of voxels remains. In this article we discuss a new approach that can extract a midsurface of a thin solid using a kernel-based approach: In contrast to other voxel-based thinning approaches, our algorithm applies a kernel onto a binary grid. In the resulting density field, opposing surface-voxels are iteratively moved towards each other until a thin representation is obtained.