Cool the aluminum molds from the outside with a fan blowing air over them. Aluminum transfers heat well, but the center of a 1-inch sugar cube cools much more slowly than the surface.

These methods are listed roughly from fastest to slowest:

| Method | How to use it |
|---|---|
| Cold-water or ice-water bath | If the mold is watertight, stand it securely in a shallow bath with the water well below the rim. Keep water away from the sugar. |
| Chilled metal plate plus fan | Set the mold flat against a thick, cool metal tray or plate and blow air across it. Good contact helps. Replace the plate when it warms up. |
| Fan at room temperature | Leave space around each mold so air can circulate over and underneath it. |
| Still air | Set the molds on a rack in a cool, dry room. This is the slowest option. |

Allow roughly 30 to 60 minutes for planning, though active cooling may shorten that considerably. Expect cooling to take tens of minutes. The estimate has not been measured for your molds; the time depends on mold thickness, pouring temperature, airflow, and contact with the cooling surface. A batch of 72 cubes will also warm the plate or water bath substantially.

Run a small trial with the same setup. Ideally, place a temperature probe in the center of one cube you can sacrifice and wait until it approaches room temperature. The surface can be hard while the center is still warm. The Culinary Institute of America recommends letting molded hard candy cool completely to room temperature before releasing it. [CIA guidance](https://www.ciafoodies.com/using-candy-molds/)

Refrigeration can help, but stop before the sugar gets cold enough to collect condensation when you take it out. Moisture damages hard candy. [CIA guidance](https://www.ciafoodies.com/using-candy-molds/)

Put a rigid cake board between the cake and the cubes to distribute the weight. Use fully cooled cubes of equal height, and test the arrangement with the intended weight for the full display duration. Humidity can make hard candy sticky or soften it, so the cubes’ ability to support the cake also depends on storage and display conditions. [University of Wisconsin confectionery guidance](https://www.gomc.com/firstpage/201209070.pdf)