Let’s make glowing gummy candies that look like LEDs! The recipe for gummy candy is simple, the legs are 3D printed, and the special ingredient to make the candies glow under blacklight is vitamin B2 powder.
For this project, you will need:
- 1/3 cup (79mL) Cold water
- 3 packets (678g) Plain gelatin
- 1 packet (85g) Jell-o (green and yellow work best)
- 2 tsp (8.4g) Ascorbic acid powder (or crushed vitamin C tablets)
- 3 Vitamin B2 powder capsules (more will not intensify the effect)
- Candy syringes
- Pyrex cup
- Silicone spatula
- UV flashlight
- Candy mold (or make your own in the next step)
As an additional experiment, we’ll add real surface mount LEDs to the inside of some of the candies.
Warning! Coin cell batteries can cause serious injury if swallowed. Keep coin cell batteries out of reach of small children!
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Making the Mold
You’ll need a food safe mold to make these candies, which you can buy in all kinds of fun shapes like bears and hearts and stars and stuff, but not in the shape I wanted, so I made my own mold.
Flash back to a few years ago when I first made LED gummies as one of my Adafruit projects. I used foamcore, hot glue, and a few packs of 10mm LEDs to construct a mold form.
I had ordered food-safe silicone, which comes in two parts, measured it by weight, and mixed the two parts very very thoroughly before pouring it into the mold form.
My colleague Paige wrote an amazing free online Instructables class on moldmaking and casting if you want to learn more about how to do those things properly.
I followed the instructions that came with my food safe silicone, including baking it at a low temp for several hours followed by hand washing. Before making the candies, put your mold in the freezer to help the candy cool faster during casting.
3D Printing the LED Legs
Before we make the candy, there’s one more thing– the LED candies need LED legs, or they just won’t look right. Way back when, Matt Griffin modeled this tiny little toothpick like piece of 3D printed plastic using Tinkercad. So I printed out a fresh batch in silver PLA filament. 16 of them print in 15 minutes (at 100% infill with no raft), so it’s easy to churn out a whole bunch. Don’t eat these plastic bits.
Gummy Candy Recipe
This gummy recipe is based on SFHandyman’s Lego brick gummies tutorial.
When I made this project the first time, I made a major oversight in not lighting up the candies themselves, so today I’m here to fix that.
Start with 1/3 cup cold water in a heat-resistant mixing vessel. Stir in 3 capsules worth of B2 powder. Slowly sprinkle in 3 packets of plain gelatin as you stir to keep it free of lumps.
Let the mixture rest on the counter for ten minutes so the water and gelatin can dissolve completely.
While you wait, you can set up a pan of water on the stove to simmer.
After ten minutes, move your mixing vessel into the simmering pan to melt the gelatin down. Don’t bother stirring it, you’ll only introduce unwanted air into the mix.
Once it’s completely melted, add in the packet of jelly dessert mix slowly and stir slowly to reduce added air, which makes the candy cloudy.
Turn off the heat and then add the ascorbic acid and stir to dissolve.
Put the mix in the fridge for about five minutes to get it to cool down and also separate into layers. As the air leaves the mixture, it leaves super clear candy at the bottom and cloudier candy up top.
Casting the Candies
The gummy stuff is a bit difficult to clean, so I set up my station with parchment to catch any drips, and my 3D printed LED legs nearby.
After the candy has cooled a little, use the candy syringe to pull up the super clear stuff from the bottom, then squeeze it into each cavity of the mold. There’s a sweet spot as the candy cools that will make the placement of the LED legs easy but also with holding power. Don’t expect a 100% yield on these… some will be much less perfect than others.
Allow the candies to cool, optionally chilling them down to speed up the process, then flex the mold to take them out.
Shine Under Blacklight
Shine a little UV light on the candies to watch them glow!
Real LEDs Inside…
To take this concept further, I pulled out my surface mount LEDs and soldered wires onto them, which I then wound around the 3D printed legs before inserting in the candies. Remember don’t eat these, they have solder on them. Even if it’s lead-free, that stuff is no good.
Thanks for reading! If you like this project, you may be interested in some of my others:
- Soldering Clean Wire Splices
- 3D Printer Filament Dry Box
- Solar USB Charger
- 3 Beginner Arduino Mistakes
- Knife Sharpening Angle Coach with Bluetooth and Arduino