Can I Pipe Royal Icing On Buttercream?
Decorating By Echooo3 Updated 4 Oct 2009 , 9:15am by majka_ze
Bad bad idea.
Royal Icing will brake to the contact with any fat.
Pipe royal icing on fondant, pipe bc on bc.
It works. 
I use IMBC and I occasionally pipe royal icing detailing on the chilled cakes. I use a royal icing made of egg white though, for strength....not meringue powder.
Two things I do advise against are 1) putting it in the fridge, and therefore 2) trying to do the detailing too far in advance. The royal icing dries and gets hard to the touch enough, but not 100%. The fridge doesn't help. (I've left slices in the fridge after parties and the royal icing softens just a little overnight.)
Here's a pic (sorry, scanned a photo!) of one iced in dark choc IMBC and then detailed with paler brown royal icing:
it is beautiful, but royal gets really hard right, i've tried to make a crown out of it
No, on buttercream or fat based icing won't RI get really hard. On my cake I have painted with RI. The brown black isn't chocolate but RI. You can see how it shines - and slightly bleeds under the lettering. I should wait longer for the icing to harden. The RI piping was not really RI hard - it got a consistency similar to Toba Garett's glaze - safe to touch but not really hard.
P.S. And when I grow up, I want to have the piping skills of Antonia!
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