Boil the sugar, water and cream of tartar over medium-low heat stirring gently until syrup reaches 310ºF (155ºC) (hard crack) or is pale brown, hardens completely when dropped on to a cold plate and snaps between the teeth when cold.
Pour the mixture onto an oiled work and sprinkle with the citric acid.
Fold in the sides and thoroughly work the acid in.
When it is cool enough to touch, roll it into sticks and snip off drop size bits.
Sift powdered sugar onto them and shake to coat.
Allow to cool and store in an air-tight container.