scraper, and holds the churn paddles stationary. As the canister turns, the ice cream mixture freezes against the inner wall of the canister. The counter-rotating scraper constantly removes the frozen product from the canister wall and returns it to the mixture. The continuing turning motion of the canister against the stationary churn paddles causes the mixture to become increasingly thick. Enough time, ice and salt produces a smooth "hard packed" ice cream. References Further reading American inventions Food preparation appliances Ice cream 1843 introductions 19th-century inventions