The efficient animation of layers of garments is a challenging task, as it requires handling collisions and contacts between multiple thin surfaces, which may be difficult to untangle once inter-penetrations have occurred. We propose a novel geometric approach, based on implicit surfaces, to robustly handle such situations. At each animation step, our method converts the possibly intersecting garment surfaces to an implicit representation. They are then combined using a new binary operator that guarantees, as output, collision free states of the surfaces. In addition to a precise modeling of contact situations, our method enables to model the relative influence of each cloth layer, based on their relative stiffnesses and thicknesses.