I'm making a wedding cake in a few weeks and the bride is requesting a detailed lace design.  The cake will be frosted in buttercream, and I plan on hand piping the lace onto the cake in buttercream as well.  I've done this type of piping before, but have never needed to follow an exact design as it was always freehand.  What is the best way to transfer the design to the cake when using crusting buttercream? 

Someone mentioned the other day about using piping gel to outline the design (on a piece of parchment) and then laying it on the cake and after you pull it away, you can see the design to pipe.  hth

I agree with The Cake Shoppe. I have used a piping gel transfer to make the design onto the cake and then piped over it. 

This is interesting. Does the piping gel make an indent in the buttercream or does it come off of the parchment onto the buttercream and leave a clear outline?

I would think something as intricate as lace wouldn't cover up the piping gel. I have seen someone use real lace to lightly press against the cake for a pattern.
 

It leaves a clear shiny outline. What are you copying? Like they said, you can press certain things into a crusting buttercream and get an impression to pipe over. Or you could make an outline on parchment with royal icing, let it harden, and press it into the cake. Then pipe over the indention. 

Yeah, I can't just use lace to make an impression, because the lace design this bride wants I had to draw by hand.  It looks like I'm going to have to try a sample using the piping gel method and see how that goes.  I just hate the fact of having to pipe this design twice per layer--once for a template and again on the actual cake! 

Thanks for the responses everyone :)

Why not use the RI method that bct806.

Oh yes, I'll give that one a try too!  Thanks bct806 and BatterUpCake :)