Cold water extraction

Cold water extraction (CWE) is useful to filter cutting agent that doesn't dissolve in water. For example, caffeine is a common cutting agent with poor water solubility.

1. Crush the substance.
2. Sift the powder with a coarse strainer, and then with a fine strainer, to make them easy to dissolve.
3. Add the fine powder to a glass jar, and add 10 times more boiling water than the quantity of the substance, and shake well for 10 seconds. This should precipitate the soluble substances in the water.
4. A fine nylon mesh (used for tea) can be used to filter out most of the impurities with water. However, to sediment all non-water dissolving cutting agents either:
   1. Letting the glass jar stand for 2–3 days. For substances that will oxidize, just let it stand for just an hour to get rid of most of the sediment, then soak the semi-clear solution with a syringe and use a syringe filter to get rid of the final sediment.
   2. Pouring the solution in a glass baking dish and carefully tint the solution to a corner where you soak it up with a large glass syringe.
5. Put the clear phase in a glass baking dish and let evaporate. Use several glass baking dishes to get more surface for quicker evaporation.
6. The substance will stick to glass surface when dissolved with water, so use a baking scraper, and finish scraping the residues with a razor blade.
7. Repeat the steps with the sediment to precipitate the 10% water-soluble substances.