Abstract: A method of selectively etching a metal component of a workpiece further comprising a ferromagnetic insulator component. The method comprises contacting the metal component with an etchant solution. The etchant solution comprises a basic etchant and a solvent. The method is useful in the context of the fabrication of semiconductor-superconductor-ferromagnetic insulator hybrid devices, for example. The etchant solution may not attack the ferromagnetic insulator component. Also provided is a composition for etching a metal, and a kit comprising the composition and a composition for depositing a styrene-acrylate co-polymer on a surface.