Spinning Disco Ball Cake - November 2010
I made a fancy cake every year for Ashlyn's birthday since she turned 2, and I continued honing my skills over the years. As my grand finale for her 13th birthday disco party in 2010, I added some electronics & special effects lighting to my repertoire to create a Spinning Disco Ball Cake that actually reflected lights around the room! I made a custom silicone mold for all the decreasing angles of the sugar glass tiles, painted the backs with silver luster dust so they reflected just like real little mirrors, used black royal icing to glue them to both rice cereal treat hemispheres, mounted onto a PVC post connected to a DC motor underpowered by fewer batteries, then hid the electronics inside a "cake" box that showed the birthday message and hid some battery color-changing lights inside old film canisters at each corner. I still love how this edible creation reflects light just like a real disco ball! :D
Spinning Disco Ball Cake
How to Make a Spinning Disco Ball Cake
I knew the party was a dance theme including a real mirrored disco ball, so they expected I might make a flat 2D disco ball...but I wanted to stretch my skills trying my first edible art movement! I had limited electrical wiring experience but no previous experience with motors or gears, and I was going for cheap, so
first I harvested the spinning base of a plastic spice rack from a thriftstore which had a screw in the center.
I found a small metal motor at a local electronics salvage shop, but it rotated really fast! It was a 5V DC motor so it could run off batteries, and I was told that if I used only 1.5V of a single AA battery instead of the full 5V as designed, it might be slow enough so the cake wouldn't fly off. Since I couldn't test everything together until all the edible pieces were on, everything was an estimate, and it still ended up spinning faster than I hoped!
I used PVC since it is easy to sanitize, so about a foot of 1" diameter thick-wall PVC pipe was the post up to the centerpoint of the ball, and the post fit into a PVC converter piece that I glued to the spinning black base, while the base was screwed to the baseboard. That way I could fit the PVC post into the motor assembly onsite after driving the entire cake 150 miles away. Radio Shack still had local storefronts back then, so I bought a battery case and a thick rubber belt, which worked pretty well for the motor to drive the center post. There wasn't much height on the motor post, so I added a dot of hot glue so the rubber belt wouldn't slip off the top while it was spinning. Since all this was inside the base box and only needed to work for one evening, I used wire nuts for my connections between the motor at the battery case, but I was proud that I thought to add a toggle switch to the outside of the box!
The bottom base was wood painted black for the screws for the spinning base and motor to anchor securely, then the rest of the base box was foamcore scraps since it was only cosmetic, with holes cut for the center post to set through the top piece into the spinning base, and the toggle switch embedded in the side wall. After assembly the entire box was painted black. I could have tried covering the base with a layer of cake, but just as well I didn't, since not even the whole disco ball was eaten at the party. ;)
...but how to make the actual ball, and how to make it reflect like real mirrors? Luckily I had one plastic mixing bowl that was very close to a true hemisphere, and the birthday girl preferred rice cereal treats over cake anyway, so there was no actual cake in this "cake" project. I made several batches of rice cereal treats, lined the bowl with plastic wrap, then filled each hemisphere completely and let it cool in shape before removing it to make the other half of the ball. I knew there was no way I would be able to transport a globe suspended on a post driving 150 miles, so I cut matching bases from cardboard, making sure the top cardboard center hole fit exactly around the PVC endcap so they nested together to avoid the top sliding off the bottom.
The top half only needed to be glued to the foil-covered base using royal icing, but the bottom half needed the center post to go through it, so I roughly carved the center hole with a long knife, then gently screwed the center post through, making sure the foil-covered base was in the proper position first! I used royal icing to glue that half to its base, but siince there was nothing anyone would eat between the two foil bases, I used hot glue to anchor the PVC endcap over the foil base to help support the bottom half from sliding down, plus a complete outer coat of royal icing to make the bottom half a solid unit with its base.
Once I knew the size of the finished sphere, I did a lot of geometry sketching to figure out what shapes and how many mirror tiles I needed. I knew from previous sugar glass work that you cannot just cut the sugar accurately once it has hardened, so I made a food-grade silicone mold from clay positives, requiring several sets of sugar
glass filling the same mold. I couldn't pour the sugar completely accurately, so the messy edge bits thankfully were able to break off by hand or be trimmed carefully with kitchen shears.
After all the sugar glass tiles were trimmed and cooled, I painted all the backs with silver luster dust, just like real mirror tiles are silvered on the back. Of course this took a lot of time, and I also made sure I had extras in case of any problems in transit! Even though the sugar glass was slightly yellow, not perfectly clear, they still looked like they would actually reflect light like I hoped. I stacked the silvered tiles between wax paper in airtight containers, made some blue marshmallow fondant & lots of black royal icing, then all that got packed safely in clean plastic in a cardboard box for the 150-mile drive, to be continued 40 miles away from the final party destination.
For the base I made homemade marshmallow fondant tinted blue, with the center post and the 4 light covers covered with fondant to match. I used food coloring pens and silver luster dust for the birthday message on the blue base. I waited until after the 150-mile drive for the fondant work, since there was too much risk of marring the surface in transit. Once the blue fondant was on the base, I set everything up to aim the lights at the four corners so the fondant would set overnight with the base, and to test the spinning speed with the rice cereal weight. I didn't add the blue fondant covering the center post until after the mirror tiles were glued and dried overnight.
Real mirrors are glass backed with silver, then placed on a dark backing for the light to reflect properly, so I made a lot of dark black royal icing to glue my sugar mirror tiles to each hemisphere separately. For even coverage, I spread a thin coat of black royal icing over the entire hemisphere first, then spread just a tiny dab of the same icing on the back of each mirror tile, taking care to only handle each tile by the edges for no fingerprints on the reflective surfaces.
I worked on foil large enough to wrap around each hemisphere so I minimized how much I had to touch the mirror tiles to avoid fingerprints. As soon as mirror tiles started going on the black royal icing, it started reflecting just as planned...hooray! When I got to the poles it was a little trickier for the final tiles than my geometry sketches, but I was still very pleased with the result. It's always easier washing off the food coloring and cleaning up for some rest after a plan comes together successfully!
Thankfully the foil protected all the mirror tiles in the same plastic-lined box the 40-mile drive to the party, then final assembly went as planned using some last royal icing to glue the two hemipheres together, but without any of the emergency supplies needed. I turned on the mini color-changing puck lights, set them in place at the four corners, and flipped the toggle switch, then dots of light started dancing on the ceiling, just like a real disco ball!
I knew it would be tricky to stick birthday candles into sugar glass, so I had found super-skinny candles that could squeeze between the tiles, and thankfully the motor was slowing down by then or we could have had a dangerous blaze!
The birthday girl and her entire family loved the Spinning Disco Ball Cake, and I felt very proud that I retired from making her birthday cakes on such a high note!