Moldmaking Pour holes

Depends on the shape of the piece, but I would put the gate at the end of the piece, for example at the knee joint, and also put an airvent on the opposite point so no air can get trapped. You will almost always need to cut off the vents on the cured piece and sand the vent down cleanly.

 

You only need to pour into the primary hole, the resin will rise up, and the barrier of silicone that forms the slot at the back of the knee (assuming single-jointed knee like CP or Volks dolls) will separate the resin.. pouring slowly the primary vent will fill up and then the secondary pushes the last of the air out and fills up.

On some other parts that I cast for my dolls (the knee peanuts and hip shells) I have both parts in one mold and they are jointed by a bridge/sprue of resin that gets trimmed off later. When I pour those parts I sometimes have to top up both pouring gate and airvent in a separate pour after they've been in the pressurepot.

The key is to pour very gently so that the stream of resin going into the gate is thinner than the width of the gate and air will be able to escape through the pouring gate as well... if you pour too quickly air can get trapped and the resin will sit on top and just fill the vent, especially if the vents are narrow. Of course you can't pour so slow the resin will start to bloom and set up before you've got it all in the mold either

 

Simon if you go and sign up at The Joint, I have several threads over there that document how I made my most recent set of molds.