Rainbow Arch Cake Topper Tutorial

A few years ago, I was searching for the perfect rainbow arch cake topper for a Trolls themed cake and could not find what I was imagining anywhere. So instead, I decided to whip out some fondant and make my own. Although the rainbow cake topper ended up looking spot on, the fondant would not dry (at least not in the timeframe I needed it to) and I was starting to panic a bit. Then I improvised. I recreated the rainbow topper, only this time I used gum paste, which dries much faster and firmer than fondant. It looked exactly the same but dried hard as a rock in about 48 hours. The cake was saved! 

I recently made another gum paste rainbow arch topper, this time for a Bluey themed cake, and realized it’s such a fun DIY that I needed to share it with you all. The main things you need are gum paste, food color gels to create your rainbow color scheme, toothpicks, and about 48 hours of dry time. Here’s a quick video of the process before you read all about it below:

PS: If you love creative cake decorating tutorials like this one, be sure to check out my YouTube channel! 

Gum Paste Vs. Fondant

Gum paste is a pliable sugar dough that is very similar to fondant in texture and workability. The main difference is that it dries much harder than fondant. And while you’d use fondant to cover a cake and make simple decorations that guests might want to eat, you should only use gum paste for decorations like cake toppers or sugar flowers since it dries rock hard. Gum paste is technically edible, but it’s not really much fun to eat (and might chip a tooth!). 

You can get gum paste on Amazon or at your local craft store that has a cake decorating aisle. If you make a lot of custom cakes, I definitely recommend having some on hand at all times for last minute decorations. It’s so much fun to work with and so durable – a win win! 

You Will Need

• Gum paste
• Food color gels of your choice (I used AmeriColor Deep Pink, Sky Blue, Electric Purple, and Lemon Yellow)
• Rubber gloves
• 1 Tbsp vegetable shortening 
• A Cup or mug
• 1-inch circular cookie cutter or round glass 
• Small paint brush
• 1 Tbsp water
• Sharp knife
• Large spatula
• 2 toothpicks 
• Wax or parchment paper

Step 1: Color the Gum Paste

Measure the gum paste into four 1-inch balls and place the rest back in the package. You may need to knead the gum paste with a little vegetable shortening to make it pliable if it seems too firm to work with at this point. 

Put on your rubber gloves (so you don’t dye your hands!) and knead food color gel into the gum paste balls one by one to create the color palette you’re imagining. I used AmeriColor Deep Pink, Lemon Yellow, Sky Blue, and Electric Purple for this color palette (one drop per ball). Be sure to store any gum paste that’s not in use underneath a cup to keep it from drying out. 

Step 2: Roll the Gum Paste

One by one, roll out each gum paste ball with your hands to make them into tube-like shapes. Each gum paste tube should be between ⅛ and ¼ inches in diameter, and about 8 inches long. 

Do this part carefully so that each colored tube for the rainbow arch is the same diameter, and store any finished tubes underneath a glass while you’re rolling the other colors out. 

Step 3: Assemble the Rainbow Arch

Place the round cookie cutter or circular glass onto your work table. This will be used as a centerpiece to build the rainbow arch around. Starting with the color that you want on the inside of the rainbow arch, wrap the middle of one of the gum paste tubes around the centerpiece to make a perfect arch, with the ends of the tube parallel to each other. I went with my Electric Purple tube for the inside color.

Dip the small paint brush into the water and paint the edges of the gum paste arch. This will act as glue for the next color. 

Wrap the next gum paste tube around the arch and gently press it around the first gum paste color to adhere it with the water. 

Repeat adding water to the edges and adding additional gum paste tubes until your rainbow arch is all together, then remove the circular centerpiece. I ended up making the inside of the arch smaller by gently reshaping it with my hands once the centerpiece was removed.

When your arch looks beautiful and even, use a sharp knife to chop off the uneven ends. 

Step 4: Add Toothpicks

Gently flip the rainbow arch over (I used a large spatula to do this) and paint a little bit of water between the arch grooves where you’ll be placing your toothpicks on both sides. Then, gently press toothpicks onto the water. 

I’ve never had any problems with the toothpicks not adhering securely with this method, but if you want to make the arch topper extra sturdy, you can use a little water to glue a thin piece of scrap gumpaste over the toothpicks. This should hold them in place very well.  

Step 5: Allow to Dry for 48 Hours 

Allow the rainbow arch topper to dry in a cool, dark place for at least 48 hours, flipping it over at the 24 hour mark so that both sides dry equally. The color of your gum paste can fade if it dries in the direct sun, which is why it’s important to keep it in a dark place like your pantry or a drawer. 

Once it’s completely dry, top your cake and be amazed! I love the rainbow arch look so much and I know it would look amazing in all sorts of colors. Perfect for a whimsical look or a modern one! 
Did you make this rainbow arch topper? I want to know how it went! Let me know in the comments below or feel free to tag @sugarandsparrowco on Instagram. I love to see your creativity!