To make dry ice in the bathroom, put on heavy work gloves, place a carbon dioxide source in the bathtub, and place a cloth bag around its nozzle. Duct tape the bag around the nozzle to protect it from the pressure emitted when the carbon dioxide source is in use. Discharge the carbon dioxide into the cloth bag. After it inflates, turn off the carbon dioxide. Remove the bag to find chunks of dry ice.
It is important to use heavy work gloves during this process, as touching dry ice with anything less can lead to frostbite. Rubber gloves and regular cold-weather gloves are not heavy enough.
The carbon dioxide source can be a canister of carbon dioxide or a fire extinguisher. Carbon dioxide canisters can be found in sporting goods stores. The canister must have a valve that can turn on and off when making dry ice. Fire extinguishers can be purchased in any department store and should be deployed according to the manufacturer's instructions during the ice-making process.
Extend the life of the dry ice by placing it in the freezer. Carefully remove it from the bag, and store it in a bowl or glass jar. If using a glass jar, make sure not to seal it, as pressure can build, causing the jar to explode.