When using a microscope, slides that are permanent can be examined and stored for a long time, while temporary slides are used for short-term observations. Permanent slides must be properly made for successful long-term storage.
Specimens must be thinly sliced and properly preserved before they are mounted on a permanent slide. Excess water must be removed from the specimen by either blotting, air drying or using a heat source. The cover slip should also be sealed to the slide.
Most permanent slides use the solid form of mounting medium, which is the most stable. Liquid mounting mediums can also be used on permanent slides. This form suspends the specimen in liquid and uses nail polish to fix the cover glass to the slide. Nail polish makes the slide semi-permanent. It is permanent if left intact and temporary if the cover slip is removed, washed and dried for reuse. Slides using the liquid mounting method must be stored horizontally and are difficult to make.
Temporary slides are usually discarded after observation; however, cover slides can be removed and sterilized for reuse. Temporary slides utilize the liquid mounting method the most. Another mounting method used is heat fixing the specimen to the slide. Immersion oil is placed on the slide, while heat is used to fix the specimen to the slide and no cover slip is used.