Archive | 2008

The finished plaster mold

After the last post on making the Imp mold, only one large side remained. Here he is boxed up once again so I can make that final plaster piece.

This is the complete mold fresh out of the mold box.

All my pieces separated clean. In the foreground are the two large side pieces, and behind are the front gusset and the poll piece. The rubber original is still seated in the back gusset. The only piece not yet removed in the small insert under the tail.

Because that piece is flush against the larger side piece, I need a notch so I can lift the piece off the casting. As this picture shows, I did get a notch cut, but I misjudged the border of the inner piece and chipped the edge. What I wanted was a notch to the outside of the piece so that I didn’t make my inner piece any smaller. It should still work, but it’s even smaller (and easier to drop and lose!) than before.

The final plaster mold is there on the left, and the reassembled rubber master mold is on the right. The rubber master can now be used to make another plaster mold, repeating the same steps I took to make this first one. The plaster molds are only good for 15-20 castings (not all of which will survive to the final glazing), so it’s important to have a “mold of the mold” so I can make more of them.

And that’s exactly what I will do if this first mold works well.

The final step is to round all the outside edges and corners and bevel the edges where the pieces meet. This tells me at a glance that this is a final production mold. It also keeps the pieces from chipping.

As I said in a previous post, this mold has been drying for more than a week now. As of today, I am pretty sure it is dry. My timing is perfect because I leave for a trip to the beach this morning, so I can’t try it yet. That means that it will be really, really dry when I first get a chance to test it. I need to know if the mold will work, and nothing will spoil a mold like trying to pour slip into it too soon. My goal was to make it impossible for me to jump the gun!

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