I experienced some problems with leaking. The mold leaked for two reasons, one was that I initially did not use enough rubber bands to hold the two parts tightly together. The other reason was that the funnels were so close to the edge of the mold that they tore the top of it a little bit, allowing some resin to leak out the top. I fixed this problem in my last mold by hot gluing the tear. In both cases, the resin leaked out the top and, therefore, wasn't a huge issue once it had settled into the mold.