I'm relatively new to baking - I'm planning on making a cake with a glitter stencil on top, however was planning to use ganache to cover the cake. If I cover the cake in ganache and put it in the fridge for an hour or two, will it get hard enough to allow me to place a stencil on top? And, after the stencil is done if I leave the cake at room temperature will it soften back out again?
Ganache will get dry to the touch after some time. If you have a dry environment, putting it in the fridge will help harden. If you live somehwere humid, pulling it out of the fridge will make condensation form and make it sticky.
If you make your ganache with a bit more chocolate than the 2:1 or 3:1 ratio, and microwave to get it soft enough to spread, it will take a shorter time to dry, if time is an issue for you.
Ganache acts a lot like buttercream, at least that is my experience. In the wintertime I've had it so dry that it didn't want to stick to the cake and recently, in the first days of heat and humidity, it was so soft it didn't want to stay firm. So if you are in a hot and humid area, I'd say use a tablespoon or so less heavy whipping cream so your ganache firms up better and then you should have no problem adding your stencil. Hope that helps.