Monday, July 03, 2006
Making a two piece mold part 10
You have probably been asking yourself "How is she going to pour that mold she has forgotten to make pour holes?" Actually I find it much easier to make the molds without pour holes and to put them in at the end. They end up much more consistent and clean and the mold is easier to seal without funny lumps of clay around the edges. So that is what I will do now.
In the top photo you can see me marking the angle of the intended pour hole on one side of the mold. I use a sharp #11 X-acto knife to do this. Just score the shape of the pour hole at a nice angle.
Next use the x-acto knife over a trash can to carve out a half cone shape. (Middle photo) Pay attention to the tip of the knife while you are doing this so you don't cut into the cavity of the mold or poke it with the tip of the knife. Also be careful not to cut too close to the edge of the cavity. You should leave at least 1/16 of an inch that is flat on the end of straight pieces like vases or tube beads. Otherwise when you pour them removing the spare may cause some cracking down the side. This does not apply to round things like ball shaped beads.
When you have all the pour holes carved into one side of the mold put the mold together and use the cut side as a guide to mark the uncut side. You can see this process in the botom photo. (Again you should hold the mold with your opposite hand not as shown in the photo I had to use mine to hold the camera) I carefully stick the point of the x-acto knife into the hole and score the plaster on the uncut side by drawing it out along the edge of the cut side. Again be careful not to poke the end in too far and poke the actual cavity of the mold. Now take the mold apart and carve out the second side of the pour holes.
Put the mold back together after the second half has been cut. Now carefully take the x-acto knife and finish off the pour holes so they line up nicely on both sides and are nice and round. When you have finished open the mold and blow out any debris that has dropped into the mold. Then put it back together and put rubber bands on it to hold it tightly closed. Use a stylus to write on an edge of the mold what it is for. (After the first dozen or so it is helpful to know what a mold is for without having to open it.) Molds should always be stored with the parting lines horizontal and on un-sealed wooden shelves. This is recommended for several reasons. 1. rubber bands sometimes break and if you have the mold stored with the parting line vertical it may fall open and break. 2. Although not usually a big deal with small molds, storing a mold with the parting line vertically can lead to the mold warping and the parting line not fitting together as tightly as it did. 3. Un-sealed wooden shelves are recommended as they allow the mold to breathe and dry out between uses. A metal shelf may rust and that may transfer to the mold plus it will not allow the mold to breathe as well.
I hope you have all found this informative and useful.