Two weeks in advance: Make bubble sticks. You will need 28 for 10 in. cake, 40 for 14 in. cake, 54 for 18 in. cake. Cut lollipop sticks in various lengths no shorter than 10 in.; leave some full-length sticks. Roll approximately 885 fondant balls, 1/2 to 3/4 in. diameter. Insert 7 to 8 balls on each stick, leaving 4 in. extended. Attach with thinned fondant adhesive. Let dry 2-4 hours. Brush balls with thin coat of Piping Gel and cover with Sparkling Sugar. Let dry.
Bake and cool 2-layer cakes (bake 4 half-rounds to create 18 x 4 in. base cake); using firm-textured batter such as pound cake. Ice smooth in buttercream. Prepare cakes for
Push-In Pillar Construction. Mark cakes in 3 1/4 in. sections. Pipe tip 9 drop strings, 1 1/2 in. deep at each division; overpipe twice with tip 7, then tip 3 strings. Pipe tip 7 drop strings, 1 in. deep at each division; overpipe with tip 3 drop string. Pipe a tip 9 ball at each division point. Pipe tip 7 bead bottom border on all cakes.
At reception: Assemble cakes. Insert bubble sticks 1 in. apart and 5/8 in. from edge on each cake. Position topper.
The drop string is traditionally used as decoration on the sides of the cake and is the basis of more ornate string work. Called a "drop" string because the line of piped icing is allowed to "drop" or fall, by itself, before reattaching it to your cake. Pipe a row of single strings or multiple strings in rows of two or three.