Pretty much, you want a smooth bowl that won't hold a greasy residue on the surface. Plastic holds some greasy on the surface, so it doesn't work well even with

Pretty much, you want a smooth bowl that won't hold a greasy residue on the surface. Plastic holds some greasy on the surface, so it doesn't work well even with good cleaning. It won't be impossible, mind you - I've used the plastic container with my stick blender to beat an egg white - but generally is more difficult, especially if you are using arm muscles to whip it instead of electricity. Ceramic, glass, stainless steel and copper all work well, though, just make sure they are clean.