How do get bubbles not to form under foundant on cakes
I can't say I wholly agree with this statement. If you've ever tried to apply fondant to a room temperature cake, you're going to have a heck of a lot more problems than just air bubbles.
I have always chilled down my cakes before applying fondant. Avoiding air bubbles is more a matter of technique in the application of the fondant and also when rolling it out prior to application. A lot of times, after rolling the fondant out, you will have air bubbles present simply from the action of kneading it. As you roll it, pop the air bubbles and roll smooth. When applying it to the cake, work the fondant smooth from the top center of the cake, working toward the edges, then down the sides. It takes some patience and skill to do this. Also, I have found the fondant smoothing tool invaluable for finishing it.
There are a ton of videos on YouTube about how to apply fondant. Here is just one of them:
Chilling is not making the bubbles form but keeping any air whipped into the BC from dissipating when applied .
After fondant is applied and the BC warms all that air has got to go somewhere and can certainly result in bubbles and blowouts.
I don't recommend applying the fondant to a cake in a sweltering environment (warm stretchy fondant will tear and like @chefpeon points out will cause way more problems than bubbles) but an ambient room temp in the 70's has always worked for me.
As peon also points out kneading and rolling can certainly trap air altho the thinner you can roll out the less of a problem you may have.
I agree about applying fondant to a well-chilled cake; I won't do it any other way. Our house buttercream is Italian Meringue. (Your mileage may vary with an american style buttercream made with butter and confectioners sugar.) A room temp cake will be more likely to sag or change shape as you are smoothing the fondant in place.
When you are kneading the fondant, you can introduce air bubbles, and the best way to handle a bubble in the fondant is as Chefpeon suggests, to pin it as you are rolling it before you apply it to a cake.
If a bubble appears after you've put the fondant on the cake, it could be that the buttercream underneath is not as smooth as it could be. Even a tiny little gap will trap air between the buttercream and the fondant and if the weather is warm, the air will expand and cause a bubble to form under the fondant.
Definitely take care when applying and smoothing the crumb coat and see if that helps. Using a fondant smoother helps because it doesn't leave palm/finger marks and it applies even pressure.
If you are rolling while kneading. Using the release wrong will cause many bubbles. If you powdered sugar/ corn starch/ what ever/ the board so it doesn't stick , when you fold the fondant back on itself you really need to remove almost all the release. If you don't you will have bubbles.
just my 2 cents
Since I "retired" (lol we all know that word never sticks around for long ;-) I am having to mostly apply the fondant by myself.
I cannot always wait until someone comes along to help with the larger tiers so broke down and invested in a http://www.amazon.com/Ateco-Inch-Silicone-Work-Mat/dp/B001FOPSGG (larger than the one shown but basically the same) .
I actually get a lot of use out of it.
It is great for cutting shape cookies... if you should happen to get a cut or deep scratch when using the copper cutters it heals right up.
Also makes for a great barrier when the Grands are decorating cookies as it sort of defines their work spaces.
A bitch to clean (this is where I miss the dish pit altho a small kids pool works pretty ok) but really easy to store... just roll up and stash.
IBC is my go to as well....unless the B&G are barefoot on the beach in 90 degree weather or in daddy's back 40 (have you ever seen anyone clean a cow pasture of the "plops"?) during the middle of a Texas heatwave.
Edited by flipflopgirl - 9/3/15 at 10:09am