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There are several filtration methods : simple or gravity, hot and vacuum filtrations. The selection of the appropriate method is typically dictated by the nature of the experimental situation. The answers to each these questions help dictate what type of set up is required.

• Are you collecting the solid or the filtrate (solution) ? If you are collecting the solid, vacuum methods are likely best as they are faster. If you are collecting the filtrate (solution), gravity filtration methods are often preferred.
• How much solution is there to filter ? If you have a large volume to filter, gravity filtration is probably the better choice. Vacuum filtration is fast but if you need to empty the flask part way through you have to release the pressure and remove the funnel to do this which increases the risk of spills and slows things down.
• How much solid is being collected ? If only a small amount is being collected, a vacuum filtration using the Hirsch funnel is preferred.
• How fine is the solid ? If it’s a fine solid, regular filtration might be very slow, so use vacuum filtration.
• Will unwanted crystallisation occur in the filter funnel ? If yes, use hot filtration.