Hi, so I'm having problems with my fondant lately because of the weather. Once I cover the cake, 5 minutes later it starts sweating and is really difficult to smooth out. My fondant will stretch and tear too if I'm not careful. What should I do? This only happens to me in the summer. Is it my buttercream? I use swiss buttercream and I use all butter. 

If there's any kind of humidity in your work space, that could be causing your issues. I know that when it is raining, fondant is a no go, but to combat that issue, I cover my cakes in front of a small fan. 

It has nothing to do with your buttercream.

Sweating is a basic physical reaction to humidity in the air.  Remove the humidity, solve the problem--so, air conditioning, dehumidifier, fan--alone or in some combination.  Covering a cold cake in a warm humid room will result in the greatest amount of sweating.  The water breaks down the fondant and/or buttercream because the sugar attracts the sweat.

That makes sense. The room I've been covering the cake hasn't been the coolest. I'll put on the air condition sooner and hopefully that'll be the end of it

Hi! Are you in a warm or humid country? I frost my cakes exclusively in ganache, let it firm up in fridge, place in room temp to sweat it out, then cover with fondant.

Once, the weather was terrible, and the fondant continued sweating, so I let the cake dry with fan overnight, and it did help! Or you might want to work in an air-conditioned room :)

I'm in LA right now and the weather is really hot and occasionally a little humid. I had the air condition on and while it went off without a hitch covering the 9 it didn't go too well with the 6. I think I need to change up my buttercream too. Maybe 1 part high ratio shortening to 2 parts butter. I think this will help too since my buttercream doesn't stay firm long enough 

Yes to the high ratio shortening to firm up the buttercream. I've even seen hot weather buttercream recipes that replace the butter completely and go with shortening and dream whip.

As for your fondant, did you make it yourself? It's the ingredients in it that react poorly to the humidity.

I use satin ice but I think what went wrong, other then the room temperature, is that my buttercream started warming up as I was smoothing. I didn't with my 9 inch but it always taking me longer to cover a 6 inch cake. Probably if I just change those 2 things then it will work out better