Optimized lead stearate multilayer crystals have been built, using a modified Langmuir‐Blodgett technique, onto glass substrates of varying surface finish. The relative ultra‐soft x‐ray peak reflectivities of these crystals were measured. The results show that under normal conditions, where thick crystals are in use, a surface finish of very much better than 1 &mgr;in. CLA is required to achieve maximum peak reflectivity. Untreated float glass, highly polished steel, and selected mica were shown to provide suitable substrates.