Black walnuts are known as one of the hardest nuts to crack. Unlike nuts like peanuts that you can crack open with one hand, or pistachios with shells that are easily shed, the way to crack black walnuts requires tools and some physical strength. Follow the method of hulling, drying, soaking, and cracking, and you'll have ready-to-eat nuts.

Hulling First

Start by hulling your black walnuts as soon as possible after harvesting; if black walnuts are left for too long without being hulled, the juices inside of the hull (the outermost covering) can discolor the meat of the nut as well as ruin the flavor. The hull stains objects it touches, including skin and clothing, so be sure to wear rubber gloves and keep surfaces covered. Using a hammer, pound the hull and remove it from the black walnut. Immediately place the nuts into a basin of water to clean them of juices and any remaining debris. According to an article from Iowa State University at IPM.IAState.edu, you can easily identify and remove "bad black walnuts" that are not fully developed; "unfilled" nuts float in the water while the good ones sink.

Drying and Soaking

Once the black walnuts are clean, you must allow them to fully dry before attempting to crack them. To dry your nuts, place them in a shallow layer (no more than three nuts deep) on something stable that can allow moisture to escape. The article from Iowa State recommends using a screen as your surface. Leave the walnuts for two to three weeks in a covered area that has good ventilation. Once dry, you can attempt to crack black walnuts, but soaking them first can be beneficial; cracking a dry black walnut may result in a shattered kernel. To prevent shattering the kernel, soak your black walnuts in water for one to two hours before cracking them to allow the shell to become slightly flexible.

Cracking Black Walnuts

Black walnuts have a shell that has a support system running from one pointed side to one more rounded side. Using either a nutcracker or a hammer, place the black walnut with the point facing up. You need to apply direct pressure to the point of the shell; either press down with the nutcracker, or strike the point of the black walnut shell with great force until the shell cracks and the kernel can be removed. Iowa State suggests using a pick and pliers to pull the kernel from the cracked shell. Also, to keep your black walnuts fresh and to prevent them from becoming rancid, store them in a plastic bag in the refrigerator for short periods of time or in the freezer for extended periods.

Source:

IPM.IAState.edu: Harvesting, Cracking, and Storing Black Walnuts