The glow in this Halloween punch isn't a photography trick. It naturally comes from the bitter alkaloid quinine, which also gives tonic water its characteristic bitterness. Because the quinine in the tonic is UV reactive, it will glow an eerie (but edible!) blue when exposed to a standard black light. But it does take a good amount of tonic to get a nice bright glow: Our test kitchen found that tonic water had to make up at least 50 percent of the volume in the recipe. To balance that bitterness, we mixed it with pineapple juice, Cointreau, pisco, and lime juice, in a riff on Pisco Punch. And in a Martha-inspired moment, we also created glowing "severed hands" by freezing tonic water in latex gloves to give the punch an extra-creepy look and keep it cold.