Spike, My experience is that there has to be enough cuts to allow
air to escape. I probably have more
cuts in my rubber molds than you have ever seen, and I get great
results. I cast sterling silver for other metal artists, as well as
my own line.I cut the sprue off, grind where the sprue was, and
tumble finish. Very rarely do any pieces have mold lines to remove.
All my customers are happy.
I made an offer on this forum to make molds for 12 people, e-mail
first. If you have mold lines,
I might be able to help. Saves so much time!
I did not understand what you said about parallel to the mold. My
cuts are quite zig zag, about 1/4 inch deep, and act as mold locks.
I have 2000 molds. Most have barely disernable lines.