I've made 100's of chocolate transfers - usually for cupcakes or 3D cake structures to be removed before cutting the cake. For this order, though, I wanted a flat image (Jayhawk - Rock Chalk!) that could be cut along with the cake & not break like chocolate would. I thought a RI transfer would be perfect! But it wasn't!.
I used the same technique but it never hardened! What happened? Could it be
1) The liquid food color I used to color the RI?
2) Technique - should I have frozen each color before starting the next one?
3) Humidity - my buttercream didn't crust well, either. It was storming.
I'm not sure why your RI transfer didn't work, but I never use them because, if they dry hard like they're supposed to, they break apart instead of slicing nicely. I always use a frozen buttercream transfer (also known as an FBCT here). They're easy to do and, if you make them the same day you deliver the cake or the day before, the colors don't run together. I'm sure it's basically the same technique, just using buttercream instead of royal icing. Now that I think about it, I DID to an RI transfer once, and it came apart precisely because it didn't dry. I ended up drawing directly on the cake right up to the time of the party. I decided it was because of the heat and humidity here in Cancún. I didn't think freezing was a part of the RI transfer method, but maybe you have to let the icing dry between applications of color!
Thanks - great to know that RI transfers break when you cut them, too! Makes me feel better!
How long did you let it dry? Depending on the size of it, it would need 24 to 48 hours at least. The rain, humidity in the air will also slow down the drying time.
If you want something that is easy to cut through, then the FBCT is the way to go.