Simple crystallization works well with large quantities of material.
Step 1. Place the solid in a Erlenmeyer flask. A beaker is not recommended because the rapid and dangerous loss of flammable vapours of hot solvent occurs much more easily from the wide mouth of a beaker than from an Erlenmeyer flask. Furthermore, solid precipitate can rapidly collect on the walls of the beaker as the solution becomes saturated because the atmosphere above the solution is less likely to be saturated with solvent vapour in a beaker than in an Erlenmeyer flask.
Step 2. Add a minimal amount of solvent and heat the mixture to the solvent's boiling point in a sand bath or water bath. Stir the mixture by twirling a spatula between the thumb and index finger. A magnetic stir bar may be used if a magnetic stirring hot plate is used.
Step 3. Continue stirring and heating while adding solvent dropwise until all of the material has dissolved.
Step 4. Add a decolorizing agent (powdered charcoal, ca. 2% by weight; or better, activated-carbon pellets, ca. 0.1 % by weight), to remove coloured minor impurities and other resinous by-products.
Step 5. Filter (by gravity) the hot solution into a second Erlenmeyer flask (preheat the funnel with hot solvent). This removes the decolorizing agent and any insoluble material initially present in the sample.
Step 6. Evaporate enough solvent to reach saturation (a large amount of solvent is used.).
Step 7. Cool to allow crystallization (crystal formation will be better if this step takes place slowly). After the system reaches room temperature, cooling it in an ice bath may improve the yield.