Start by pre-chilling your freeze dryer, with the metal trays inside, for at least 30 minutes.

Carefully pull each metal tray out about 1/3 of the way, one at a time. Pour 3-4 cups of milk into each tray, filling it about 2/3rds of the way to the top, leaving room for expansion when the milk freezes. (Small and medium freeze dryer trays will hold less.)

Make sure all the trays are back in the machine, close the door, and turn the machine on for a full freeze-dryer cycle. It should take about 30 hours to complete, but will vary based on outside humidity and temperature.

When the cycle is complete, open the machine and check to make sure the milk is completely dried. If not dry, add a few hours extra dry time. If dry, remove the trays from the machine and pack for storage.

Set the machine to defrost and allow it to defrost as you store the freeze-dried milk powder.

For long-term storage, freeze-dried milk should be stored in mylar pouches with oxygen absorbers. If properly stored, it should keep for 10+ years. For short-term storage of 1 year or less, a mason jar with a tight sealing lid will work just fine. Refrigerate the milk once rehydrated.

To rehydrate the milk, place 1 to 1 1/3 cup of freeze-dried milk powder (75 to 100 g) into a quart jar. Fill the jar with cold water and shake for about 30 seconds to dissolve the powder. Enjoy immediately, or store in the refrigerator.