No, this will cause the solution to boil over. ~never add a solid substance to a solution at or near the boiling point~ What is the purpose of using a pre-warmed filter funnel avoid formation of crystals that can occur if the solution you are filtering cools down when it comes into contact with a room temperature filter funnel. The filtrate from the hot gravity filtration should be clear and colorless. Charcoal has somehow passed into the filtrate and a second hot gravity filtration must be performed. Crystal formation is dependent on concentration of the solute and temperature of the solvent and is also dependent on what solvent(s) are used. A solute or compound that is extremely easy to solubilize in a solvent is. The more slowly the crystals grow the more pure they are. How did we collect the crystals in this experiment? suction filtration using a buchner funnel.