In some cases, excess precipitate can appear on TEM grids from over-staining. To clean them:
Place a large drop of 5% acetic acid on a taped down piece of parafilm. Place a second drop of distilled water a short distance away.
Place dirty grid in acetic acid solution for 1.5 – 2.5 minutes depending on how severe the excess stain is. If the grid is left for too long in the acid solution the stain in the tissue will be too light to capture.
Move the grid to the distilled water for 10 minutes. Remove grid, blot off any extra water by touching the side of the grid on filter paper and then shake grid dry using fine forceps.