Bubbles under buttercream on iced cake?

[ohmyganache]

Anyone have an idea of why in the world this is happening? It doesn't happen often, but it does sometimes... and it drives us crazy!!! The bubbles just seem to form. We can deflate them, smooth it over, and then they're be back 20 minutes later? It's baffling...

Help me figure out this problem! We certainly don't want this happening after the cake leaves the shop...

[pastrygirl]

Something alive is in there and trying to get out! Does this happen to fresh cakes or only after a few days?

[Lisa Shock]

Is the cake soaked in alcohol?

[JeanneCake]

can you give us more info on the kind of buttercream (swiss? italian? veg shortening based?) and how you assemble the cakes (two layers cake/ three layers cake).

Does the bubble happen only on the same kind of cake (variety) and not on others?

My first thought was it was an air pocket in the filling layer and as the cake settles, the air pocket pushes on the outer layer of buttercream.... and that's what makes me ask about whether it happens on all kinds of cakes you make or just a certain type.

[ohmyganache]

Okay...

Fresh cakes only. Sometimes, minutes after putting the final coat of icing on.

Italian buttercream. Italian meringue mounted with butter, salt, vanilla, and lemon juice. No shortening.

I don't seem to notice a pattern on the cake itself, but I'll pay attention to which cakes the bubbles form. All the cakes are layer cakes, most three layer, but the one in the picture was a two layer tasting cake. Also on at least one large multi-tier cake. That one was red velvet actually, and we mostly do either chocolate or vanilla cake filled with ganache, pastry cream, or buttercream.

What we're thinking is that there is a pocket between the crumb coat and the final coat, so we're been extra vigilant on making the crumb coat super-smooth (which kinda sucks, of course, because it takes more time...)

[ohmyganache]

Sorry, I missed a question... the cakes are not soaked in alcohol.

[Nayan Gowda]

What rising agent do you use for the cake?

[pastrygirl]

This is really weird, I am so curious. You said that the bubbles keep reappearing even after smoothing them out, which makes it sound like some sort of gas buildup, like maybe the filling had fermented or there was yeast involved. If it was just an air pocket, would it reappear? How do you even get air pockets in buttercream?

CSI: Pastry!

[HungryC]

I'm wondering about temperature...are the layers room temp when frosted, chilled, or frozen? If frozen/chilled, maybe something happens as the cake warms to room temp? Or something caused by the temp differential between the icing and the cake?

[gfron1]

My first thought was just settling, but now I wonder if whomever is mixing is not mixing well enough and your leavener is being left if pockets. Any chance your baking soda/powder has clumped?

[ohmyganache]

The cakes are iced when they're cold. We chill the cake so that it's easier to handle (it's quite tender when room temp, which makes them really nice to eat!). I had thought that may have something to do with it... perhaps as the cake warms, the cold air present in the cake structure warms and expands. Does this sound reasonable?

The cakes are getting mixed well enough... the baking powder is sifted into the flour before being added. And I don't think that I mentioned the cakes are standard yellow cake... butter, sugar, flour, eggs, milk, vanilla, BP, salt... creaming method, baked in full sheets and cut to size.

We also crumb coat the cakes, chill them overnight in the fridge, and then put the final coat on. So there is a temperature difference there as well.

I think we're onto something here...

Pastrygirl... I haven't noticed that the filling makes a difference, but I'll take note when it happens again and see if there is some sort of pattern. I really hope it's not a fermentation issue! Ewwww! I can't imagine that would be the case...

[JeanneCake]

I usually crumb and final coat the same day; I find that the second buttercream coat doesn't adhere as well when I chill the crumb coat overnight. I notice that it "smears" (for want of a better word) as I'm applying it; it happens more when the final coat is thinner than usual. I also use Italian Meringue but I'm not using lemon juice or salt in mine.

I build the cake, wrap in plastic and let it sit overnight; then the next day apply the crumb coat and final coat. Usually about an hour apart, depends on the work load.

If it were happening to all of your cakes, all the time, this might be the culprit.

[chefpeon]

I've had this happen to me a few times when I've iced a cake either frozen or chilled and as it warmed up and "settled" the bubbles appeared. Really annoying. Make sure you stir the air out of your buttercream before you apply it or put it in an icing bag.

[ohmyganache]

Thanks chefpeon, I think this is what the problem was. The gas inside in the air bubbles expanded as it warmed, pushing its way out of the buttercream layer!

[chiantiglace]

I have never had anything like that happen to me but I would be a bit surprised if the air was coming from the buttercream itself. I wish I could take a look at the cake itself to get a better idea but I wouldn't be surprised if the sodium bicarbonate did not get dispersed properly, and if there were bits that did no hydrate through the baking process they would still be hanging on in pure form never converting to carbon dioxide. So I would think that after breaking the cake down and coating it with the buttercream you may be exposing some of the BS to moisture thus starting the chemical reaction slowly at room temperature. That would explain why the air is bulging at small and specific places and not in a large web or lines around the cake where the layers are.

But then again, its just a theory.

[K8memphis]

Cake farts. I have been observing this phenomenon for over 20 years. So far I can detect zero common denominators other than it's iced cake that swells under the icing from a collection of air and will burst or stay afloat indefinitely.

The prevention is to slide a pin through the icing into each layer of cake--I use a hat pin in an unobvious place when I remember to do it. Or when circumstances remind me to do it. This of course is also the remedy before it bursts.

Completely room temperature cakes, whatever stages of being chilled or frozen, buttercream, meringue bc, fondant---hmmm, I guess I've never seen ganache do it (have I? hmmm, can't remember...) so anyway cakes fart--try the pin poke to have a release valve and see if that doesn't help to a great extent.

Actually a CakeBuddy on another forum has just suggested before the final coat, placing a ceramic tile on top of the plastic wrapped cake for a while to help expel any gas. (Air is gas.)

[K8memphis]

Previous cake fart thread.