Defoamer 105 is a food grade silicone based foam inhibitor used widely in commercial brewing. Prevent boil overs on the hot side, add a few drops per gallon for a nice rolling boil. On the cold side, fermcap keeps the krausen in your fermenter to 1/2 inch. Allows you to brew slightly larger quantities in your existing fermentation vessels. Use only two drops per gallon at the start of fermentation. Used in the fermenter, it increases the bitterness in your beer (retained ibus) by about 10 percent . Comes with dropper Lid. This 2 ounce bottle is enough for 240-250 gallons.