I did this at TechShop Menlo Park. http://www.techshop.com
Once you've made wax items you want to turn into metal, before imbedding them into a mold you have to create sprues.
Step 1: Items You Need
I'm working with hard wax so I used a crockpot to make it malleable. You need oil to prevent wax from sticking to your hands. Of course your wax sculptures and a sheet of plastic to cover your work area. Popcorn in lower left is helpful to snack on but optional. :)
Step 2: Making the Main Pour Line
The most important sprue will serve as a channel through which molten metal will be poured into the cavity the lost wax will create in your mold. I usually make it conical and attach the smaller- tip end to the sculpture. I am attaching it to the base (bottom) of my sculpture so it will be easy to cut off and the mark will be hidden once this piece is aluminum. The wider edge of the sprue will serve as a mouth through which to pour aluminum.
Step 3: Shaping
Shape your sprue making sure its firmly attached to your ipiece and use cold water to harden it so it soesn't slump.
Step 4: Air Sprues
Several smaller sprues will be attached to your piece serving as air lines. They will allow free flow of molten metal to enter fully into the cavity without intrapping air on its way into the mold. These sprues will be thinner and will be placed someheretowards the sides of the bottom of your wax piece. They cannot be pointing sideways or downward as it will allow metal to run through the mold and out. They have to curve up! Now you are ready to make a mold. Follow my next instructable on making a mold for lost wax casting.