OK, ok I'm exaggerating a bit... In this Instructable I'm going to show you, how to make candy that "glows" under UV light and looks like the fictional mineral from the superman myths.
For some time now, I've been playing around with Fluorescein, which is a dark red powder soluble in water and alcohol. It is commonly used as a fluorescent tracer. Though it is used e.g. in eye drops and biochemical research, it can cause adverse reactions (like nausea or vomiting). Because of this, even though only very small amount are needed I don't think it is safe enough for candy (and it is not easy to get).
Sadly most phosphorescent substances aren't classified as "food grade" (even though they are not toxic). In most "glow under a black light" food Quinine is being used, which is in Tonic Water (in very small quantities). In my opinion for candy it is not suitable thought, because of two major reasons: 1. the bitter taste and more importantly 2. it's melting point is very close to the temperature you will need to make the candy.
So I had to find an other easy to get food grade chemical with a high melting point. My solution: Riboflavin, better known as vitamin B2 or additive E101. It can be found in most vitamin pills, is not toxic and fluorescents yellow under UV light (and even under direct light). The only set back is, that it is destroyed by exposure to light, but in our case it should matter because the process is pretty slow. Btw. that is the reason why you should buy your milk rather in opaque containers and not in glass bottles.
OK enough with the boring science stuff, lets go kill superman ;-)
Becky Stern from MAKE Magazine made an amazing video, on how to make the candy:
Step 1: What you need
- 250 g sugar
- A vitamin B2 pill (just ask in your apothecary, or on amazon.com (half a pill is enough)) (the one I used had 15mg per capsule and I used three capsules, don't use more than that, it will not enhance the effect)
- green food colouring
- mint oil (or any other type of oil to give your candy a nice taste)
- aluminium foil and/ or powdered sugar and e.g. quartz crystals (to make the forms)
- UV light
- a small pot
- candy thermometer