The best way to make smoke come out of a volcano cake is to use dry ice and water. Dry ice is carbon dioxide in solid form. It freezes at a very cold temperature and transforms directly from a solid to a gas in a process called sublimation. When dry ice mixes with water, it creates a cloud of carbon dioxide and water vapor that is non-toxic and provides the effect of smoke coming out of a volcano.
The first step in creating the smoke effect for a cake in the shape of a volcano is to obtain dry ice. Typical retail stores do not carry dry ice for sale. Instead, consumers can find it at businesses that specialize in ice distribution and other industrial services. The Dry Ice Directory offers a listing of businesses that sell dry ice throughout the United States and in other parts of the world. Dry ice is much colder than ice made from water and can cause skin damage. Consumers should wear gloves when handling dry ice and take caution not to store it in a sealed container.
The next step is to create a space for the dry ice inside the cake. Baking the top portion of the cake in a Bundt or ring-shaped pan creates the correct shape. The baker can then place a drinking glass inside the cavity in the center and fill it with small pieces of dry ice. The dry ice sublimates into a gas quickly, so it is best to do this right before serving the cake. Add small amounts of water to the dry ice in the glass to create the full effect of a smoking volcano.