Spread Epsom Salt (Hydrated Magnesium Sulfate) on an aluminum foil covered pan.
Place in the oven on 400°F for about one hour, or until the salt becomes gray and ash-like.
Place your now anhydrous magnesium sulfate into a storage container and store away from moisture.
If it becomes hydrated again, the process can be repeated.
NOTE
This can also be done on the stove top/oven ring, however it should be noted that as the Epsom Salt releases water it will stick to the inside of your pot but as it reaches complete dehydration and becomes grey and ash like it will unstick and become a powder.
