Wash and peel the turmeric roots.
Grate the peeled turmeric.
Add to a baking tray.
Dry in the oven at 150°F (or place in the sun to dry for a day).
After an hour in the oven, stir and leave for another hour.
After the second hour in the oven, stir again.
Bake until the gratings are completely dry and crisp.
Remove from the heat and leave to cool.
Add the crispy turmeric to a spice grinder.
Grind completely.
Sift.
Regrind larger pieces.
Place in an airtight container.
Store in the fridge for years (or on the countertop for months).