I am sectioning 50um frozen spinal cord samples and trying to stain them with cresyl violet. At the end of the staining protocol, after the samples were washed with xylene, I dry the sample in preparation for mounting using aqua-poly mount medium. However, when ever it dry and mount the samples, the spinal cord sections turn completely black under the microscope but when I keep the slide wet with xylene and add the mounting medium immediately the sections appear normal. These section however always contain many bubble rendering the slide pointless. How can I prevent sections turning black without keeping the slides wet before mounting.
we where able to restore some of these darkened sections by opening up the coverslip and applying xylene. These slide however, also suffered from the presence of many bubbles.