Sections from gelatin embedded brains will not wrinkle or pucker when mounted on slides if the sections are first passed through an acetone, ammonia, acetate buffer-ethanol sequence. Species to species differences are adjusted for by altering the salt concentration and/or the pH of the acetate buffer.
Switzer III, R. C. (1979). Wrinkle-free mounting of sections from gelatin embedded brains. Neuroscience Letters, 12(1), 103–105. https://doi.org/10.1016/0304-3940(79)91488-5