Thanks for your in-depth answer.  I will try that process out later on, when I have the time.  The mold I need to produce need not be realistic. I am actually copying a client's logo, we copied it from their concrete bas-relief.   The bottom is square and flat, the top has the flower design(hibiscus-like with many thin petals).  The pastry chef I work with recommended using silicone vs the plastic because the details would come out better.  Now I'm trying to figure out if it is worth the trouble.  I have somebody who has carved the logo in hard bar soap/clay (that was th requirement of the custom-made mold maker).  Thanks for your help!