To mount very thin crystals onto cryoloops, first dip the nylon loop into 0.5% Formvar solution (Fluka # 09819) to form a thin film. The film provides extra support for fragile crystals, and can result in much sharper reflections with just slightly higher background. To clean the loop, dip it in alcohol to dissolve the support. Two notes: (1) the technique works only for crystals grown without organic solvents, and (2) take precautions not to breathe vapor from the formvar solution–the solvent is 1,2 dichloroethane. Formvar is a standard support for electron microscopy grids.