Samples should then be spun, washed and re-suspended in distilled water or one of the above mentioned buffers. Samples may be taken straight from the culture plate using method C. Care should be taken with unfixed bacterial or viral samples. The final pH should be 7.0. Place a large drop of this mixture onto a formvar grid then remove almost all of it. Alternatively, place a large drop onto the formvar grid, leave for 30 seconds, then remove the excess with a filter paper.
Some methods advocate a wash in distilled water after drying.
In practise this is usually only necessary when using a buffer which becomes crystalline when dried or when the sample is too thick on the grid. If this is done dry the grid again before viewing. View under E.M. Method B. A suspension of cells is made in distilled water or a suitable buffer. A drop of this is applied to a formvar grid. When the suspension has partly dried the grid is washed by touching it three times to the surface of a drop of distilled water.