To prepare slide, pass cleaned slide through blue part of burner flame several times to remove residual dirt. Cool slide, flamed side up, on paper towel. Mark wax line across slide to give area 2.5 x 4.5 cm. Place large loopful of suspension in center of slide adjacent to wax line. Tilt slide, letting drop run down center of slide to end. If drop does not run evenly, slide is dirty. Discard it. Air-dry slide on level surface.