Halloween is just around the corner! Prepare to panic bake as many spooky sweets and tricky treats as you possibly can over the weekend!

I'm planning to bake a lemon tart, mainly because the filling is quite light and seems as though it would take colouring pretty well. Also because lemon tart is delicious and should never need justification.

My question is: Is there anything that I can add to my filling that will make it glow in the dark?

The ingredient(s) must:

  • Make it glow (obviously)
  • Survive the baking process without breaking down into something that doesn't glow
  • Not make the lemon tart taste offensive

I must mention, as every google search has failed to make this distinction: I am looking for solution that glows in the dark, not a solution that glows only when exposed to UV light, although one that does both would be acceptable.

  • 8
    Radium? (I have no idea how it tastes, but there was no requirement that it not kill whoever eats it). Of course, if it was something in a glaze afterwards, it doesn't need to be heat stable. I've heard the stuff in glow sticks is non-toxic, but you have to deal with the broken glass capsule.
    – Joe
    Oct 25, 2017 at 15:20
  • 4
    Radium tastes terrible, allegedly :(
    – Korthalion
    Oct 25, 2017 at 15:34
  • 3
    Makes your tongue all tingly too.
    – GdD
    Oct 26, 2017 at 8:34
  • 3
    @Joe Perhaps non-lethal, but not non-toxic: illinoispoisoncenter.org/my-child-ate-glow-stick
    – Erica
    Oct 26, 2017 at 12:12
  • 4
    @Erica : hmm ... "Toxicity Level: Minimally toxic in a small amount such as a taste or a lick." ... " It is important to wash off the liquid as soon as possible after the glow stick leaks. If the liquid sits on the skin for extended period, more serious skin injury can occur (such as blisters or chemical burns). " Well, good thing there was no requirement for the people eating it to live and/or not have chemical burns.
    – Joe
    Oct 26, 2017 at 13:26

1 Answer 1


Use bioluminescence. Glow worms are edible and they are phosphorescent. You could make powder from organisms that have phosphorescence (glow worms). Crush them, sprinkle them on top of lollipops or you could try crushing up GloFish: https://www.foodprocessing-technology.com/features/featureglowing-sushi-experimenting-futuristic-food/ These will glow in a dark room, but only faintly. You can use blacklight to enhance the bioluminescent ingredients response. Here's some nice pictures of fluorescent dye from glowing jellyfish for glow beer using a yeast that responds to "UV or blue light" according to gizmodo. No UV light needed. https://www.eater.com/2016/12/8/13886320/glow-in-the-dark-beer-jellyfish-genetic-engineering Also check out the links at the bottom of that Eater article on glowing beer, glowing udon noodles, and glowing ice cream.

An alternative to food that glows on is own is to use the more commonly available neon colored dyes could look like they glow. These super-bright hues won't give off their own light for a true glow, but will reflect lots of ambient light.

Disney has done a lot of research on making glowing food and they've gone with the LEDs or light-sticks inserted into food. The effect is food safe and dependable, or else they wouldn't use it: Disney's InfinityAide or Fairy Floss or LightSaber Churros Perhaps bake your pie in two pieces and then drop a glowing light cube inside your lemon filling and then plop on the pre-baked top? Or maybe make a crust that has holes in it that you can poke a few small lightsticks into.

The most common way to get a glow in the dark effect is to use UV (fluorescent dyes) because many food safe ingredients (such as tonic water and caramel) respond to UV wavelengths. The UV causes the ingredient to give off its own light (fluoresce). However, I'm not sure if the quinine from tonic water will survive baking. Lots of websites show people using tonic water on their cup/cakes after covering them with jello, like this one https://www.youtube.com/watch?v=qTh4K9Jmh0g There is research about them at Rutgers. Apparently these edible fluorescent food colors are routinely added to food or pharmaceuticals: Allura Red, Sunset Yellow, Brilliant Blue, Fast Green and Tartrazine, a yellow-colored dye. Read more about fluorescent food dyes at: https://phys.org/news/2015-02-fluorescing-food-dyes-probes-quality.html#jCp

Anyway, you could avoid UV and go for blue light. Some things that will flourescen under UV will respond to blue or purple LED light.

  • 2
    "I must mention, as every google search has failed to make this distinction: I am looking for solution that glows in the dark, not a solution that glows only when exposed to UV light, although one that does both would be acceptable."
    – Korthalion
    Feb 12, 2018 at 11:00
  • amazon.com/Neon-Purple-Green-4-pack-Color/dp/B004MNYB6U/… Maybe the illusion of glowing, combined with a light source (e.g. glow sticks or LEDs)?
    – anjchang
    Feb 14, 2018 at 0:38
  • 1
    The terms are "flourescent" vs "phosphorescent" ... Feb 14, 2018 at 10:46
  • 1
    Quinine would plausibly survive baking (melting point is 177°C, and that won't be reached if it is dissolved in water which doesn't dry up during baking - and even melting doesn't necessarily mean the fluorescence will be broken, AFAIK). However, quinine is quite bitter, so flavor is affected (depending on quantity used, of course).
    – gustafc
    Sep 18, 2019 at 10:06
  • 1
    @gustafc chemically speaking the thermal stability of a compound and its melting point have nothing to do in common.
    – Alchimista
    Nov 30, 2020 at 9:44

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