I never use American Crusting Buttercream so I am not sure how it behaves in the fridge.  I am painting a cake covered in it.  

Can I place the painted cake in the fridge?  Will the paint run due to condensation?

Any advice or insight is appreciated!

I have never painted on it but have used it almost exclusively.  To help prevent condensation I suggest wrapping the cake in loose cling/plastic wrap then put it into a cake box.  When you take it out leave it as is for at least 1-2 hrs.  Most/any condensation will form on the covering and not the cake.   My thought is the pain might/probably run if not treated as suggested.

I do exactly as kakeladi suggested except, I put the cake in the box, then wrap the whole box in plastic wrap to seal.  I do allow them to come to room temperature before unsealing the box and have never had a condensation problem.

Thank you!  So just to make sure I understand...

1. you paint on American Buttercream cake

2. then place in box

3. wrap  box with plastic and refrigerate

4. Allow cake in box to sit at room temperature for at least one hour before opening. 

And the paint is ok?

Yes, except I usually let it set out a little longer.  Depends upon the size of the cake.  I've never had it to run.  If the cake has come to room temp, it is perfectly dry.  By the way, my house is always cool because it is are conditioned in the summer, so it is not a super drastic transition in temperature.

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