Gelato looks soft in a shop display case, so what would make that same gelato turn brick-like after you bring it home?

Answer: Storing it too cold

Storing it too cold ✓ — Right. Gelato looks soft in the shop partly because it is served warmer than hard-pack ice cream, so its dense, low-air body stays pliable. Put that same gelato into a very cold home freezer and it can turn brick-like. Temperature can look like a difference in style.

Adding less churned air — Not quite. Less churned air is one reason gelato tastes dense, but it does not by itself explain why the same gelato hardens at home. Low overrun actually leaves less air to interrupt the frozen matrix, so cold storage can make it feel especially firm. The missing clue is the warmer shop case.

Using a milk-heavy base — Not quite. Gelato often uses more milk and less cream than American-style ice cream, but that is not the whole softness story. A milk-heavy, lower-fat, lower-air product can be quite hard if served too cold. The texture you see in a display case is partly a matter of serving temperature, not just ingredients.