The discussion centers on the use of denatured alcohol as a fuel for an indoor lantern designed for ethanol. Users report difficulty finding pure ethanol at local hardware stores, which typically stock denatured alcohol instead. Denatured alcohol, primarily composed of ethanol with added toxic substances to prevent consumption, is deemed suitable for use in the lantern. It is noted that denatured alcohol is flammable and can be dangerous if the lantern is knocked over or if the flame is not visible. Some participants suggest alternatives like Everclear from liquor stores, although it is more expensive. Safety concerns are raised regarding the clear flame of ethanol, which can be hard to see, emphasizing the need for caution when using the lantern indoors. The conversation also touches on the composition of denatured alcohol, clarifying that methanol is no longer commonly used as a denaturing agent due to its toxicity. Overall, denatured alcohol is confirmed as a viable option for fueling the lantern, with safety precautions being paramount.