Smectic A films with a positive dielectric anisotropy can be switched to homeotropic textures by application of sufficiently high AC electric fields. They can relax to a light scattering state when the field is removed. The transition between the homeotropic and the light scattering focal conic texture is attractive for display applications, but Le Berre and Hareng found with 4–4′-cyano-octyl biphenyl (8CB), that the relaxation was slow and limited to a range of 3° C at the SA-N phase transition. We found that the relaxation can be enhanced by suitable surface treatments. With conventional polyimide coatings the relaxation to the scattering state occurs through the entire SArange (12° C). Observations on samples with differently treated polyimide coated surfaces indicate that the surface roughnes facilitates the relaxations. The relaxation time depends strongly on the temperature. It increases from 50ms near the N-SAtransition to 0.3s at the SA-solid crystal transition. In the range of 5 to 50μm, the contrast and the relaxation time are nearly independent of the sample thickness. The drive voltage is temperature and thickness dependent. For a 5μm film it was below 20V over the whole temperature range. Comparing a smectic A shutter with a typical PDLC device we found that the contrast ratio is smaller, but the non scattering state is completely haze free.