Why do cake fillings bulge out and how can you prevent it? Here are the top five most common reasons why your fillings are likely to bulge including solutions on how to correct the problem.
Bulging Cause #1
Because Air Got Trapped Inside the Cake
This is one of the most common yet unexpected reasons why your cake fillings might bulge. It has everything to do with how the filling layers are added. If you don’t push them all the way out to the edge, little caverns form where air pockets get trapped beneath the frosting. Once the cake goes on display, it warms up. As it warms up, the fillings get softer. At the same time, gravity exerts pressure from above, which pushes the air pockets out.
Solution: Fill Layer Cakes in the Baking Pan
The way to solve this problem of air getting trapped inside the cake is to build your layer cakes inside the baking pan instead of free-form. Here is the link to my video series showing How to Fill Layer Cakes in the Pan.
Bulging Cause #2
Because the Filling is Too Soft
This is the most obvious culprit. A soft filling is more likely to get squished. If it spreads when you spoon it onto a plate, then it’s definitely going to squish out of a cake. However the filling recipe itself is not necessarily the only variable here. The consistency, size, and form of the cake sponge may also impact how the filling performs. Tall cakes, stacked cakes, and dense, heavy cakes exert more pressure on the filling layers below, increases the chances that a soft filling will squish out.
Another variable is the how the cake is finished. The more plain the outside of the cake is, the more likely bulging filling layers will show. For instance, a cream cheese filling recipe that holds up beautifully in a 10” double layer carrot cake with nuts around the sides may not perform as well when it’s used in a 12” triple layer wedding cake with a plain design around the sides. On the garnished cake, the nuts hide the bulge whereas the plain frosting finish is more prone to showing its flaws.
Permanent Solution: Use Reliable Filling Recipes
If a filling is so soft that it requires a piped dam around the edges of every layer, I would omit it from my menu. There are plenty of stable fillings out there so why use a squishy one? It’s a pain dealing with soft fillings and all the problems that result from using them. Especially when it comes to once-in-a-lifetime events such as weddings, I prefer to play it safe by using reliable fillings. Here is a link to 11 filling formulas that have worked reliably for me:
Temporary Solution: Piping a Dam
If you happen to be attached to a particular filling recipe that is too soft but you still want to use it because it’s delicious, you can always pipe a dam of stable buttercream around the edge of your filling layers to help hold the filling in. Just keep in mind this will create more work during the filling stage, especially if you are making a large wedding cake with multiple tiers. You will need both extra frosting to make the dam and extra time to fill your piping bag over and over as you add the dam.
Bulging Cause #3
The Filling is Too Thick
Solution: Make Thinner Layers of Filling
It’s more optimal to make thin layers of cake alternating with thin layers of filling versus a two thick layers of cake with one huge layer of filling in between. My maximum suggested thickness for wedding or stacked cake fillings is ½” – ¾”. My maximum suggested thickness for carved or sculpted cake fillings is ½” or less.
Bulging Cause #4
Any time you make a layer cake, you have to include some sort of infrastructure to hold it up (I prefer to use wood dowels for cake supports). Certain types of infrastructure such as thick dowels or SPS will exert pressure on the outside of the cake. This increases the chance that a cake will crack on the finish. It also increases the chance that fillings will bulge. The wider your infrastructure elements are, the more cake you displace. Keep in mind that width is not the only factor involved. The more dowels you add, the more you disrupt the inside of the cake. For this reason, it’s important never to use more dowels than are actually needed.
Solution: Core Out Space for the Infrastructure
The way to avoid displacing too much cake is to core out space whenever you are planning to insert a thick column. You can core out your cake using an apple corer or bubble tea straws. I recommend and inserting dowels right after the frosting stage, when the cake is somewhat soft from sitting out at room temperature because you were working on it. Then it will be a little more forgiving. Don’t attempt to core out a cake when it’s frozen. Follow this link to read my video tutorial on how to use wood dowels in cakes.
Bulging Cause #5
Lack of Refrigeration
Unless you are working entirely with ingredients that are stable at room temperature, which is unlikely, it’s necessary to store your cake in the refrigerator. If you leave it out overnight or for hours upon days and it has butter in it, the fillings are going to soften considerably. The longer a cake sits out at room temperature, the softer it will get. If you transport a cake when it’s completely soft all the way through to the center, you can almost guarantee that your cake layers are going to shift and your filling layers are going to squish out.
Solution: Chill the Cake
The refrigerator is an excellent tool for maintaining the structure of a cake while you’re working on it. The cold temperature makes frosting and fillings more firm, which makes the whole cake more stable. A chilled cake also transports more easily than a room temperature cake. The only drawback to using the refrigerator is that condensation will form on the surface of the cake. Follow this link to watch my video on the topic: Solutions to Cake Condensation.
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