Surface viscosity is a fundamental property of fluid interfaces: it quantifies their resistance to deformation and controls many physical and industrial processes. It plays a key role in bubbles coalescence, the drainage of foams or the thickness of thin liquid coatings. Yet, despite decades of experimental efforts, measuring this property remains a real challenge. For many common surfactants — such as SDS or TTAB, found in most foaming systems — the surface viscosity is simply too small to be measured with the existing interfacial rheology methods. As part of this project, we aim to develop a new experimental method to measure these extremely small surface viscosities. The idea is simple but original: we will perform the measurement at the surface of an horizontal soap film, using a 10 micrometer magnetic probe.