Maes C., Shlosman S.B. Freezing Transition in the Ising Model without Internal Contours (184K, PostScript) ABSTRACT. We consider the low temperature Ising model in a uniform magnetic field $h>0$ with minus boundary conditions and conditioned on having no internal contours. This simple contour model defines a non-Gibbsian spin state. For large enough magnetic fields ($h>h_c$) this state is concentrated on the single spin configuration of all spins up. For smaller values ($h\leq h_c$) the spin state is non-trivial. At the critical point $h_c \neq 0$ the magnetization jumps discontinuously.