To make a floating lantern, it is crucial to ensure that its weight is less than the volume of air it displaces. The envelope's weight and volume can be easily measured, while the weight of the hot air inside varies with temperature; for instance, 24 liters of air weighs about 29 grams at room temperature. Understanding the relationship between temperature and air density is essential, as the weight of the air decreases linearly with increasing temperature. Experimentation is necessary to determine the optimal temperature for the hot air within the lantern. Resources on hot air balloon construction may provide additional insights for achieving successful buoyancy.