Friday, November 21, 2008

From the comments

Becky Turner had a good question in the comments, so I thought I'd answer it here where I could use pictures.
"Im curious bout something.. why cant you pour the rubber copies from the original mold? cant you coat the original rubber mold mold with mold release and cast the rubber your using into it? if not..why?"
I believe Becky is speaking of the original rubber mold that would have been used to cast the foal in resin. I'm not using that mold because the mold lines for the ceramic version will be different from the resin one, and the pieces of the mold are actually as important as the original inside it. That's because while the rubber original (which I'll pour when all these pieces are done) defines the contours of the foal, the rubber mold sections define the contours of the mold pieces. I'm not really making a mold of the foal so much as I am making a mold of the mold.

What I am doing with all this clay is essentially sculpting the inner mold pieces. On the first side I was sculpting them in the negative - making the indention for that side of the inner piece to fit inside. Then on this last side I sculpted them in the positive.

You can see this pretty clearly on this Finn mold. The bottom piece was the first part was poured, when Finn was sitting on a relatively flat "bed" of clay. This might be easier to visualize if I flip the mold over here:

Imagine the blue area is the clay holding the horse for the first rubber pour. The white plaster is the first rubber piece made.

Flipping the mold back over again, now imagine that the yellow area is the rubber I poured in the first step. At this point in the process, that rubber is now holding the original in place. The blue area is the clay I used to form the gusset. (If I were to turn this mold around, you would see another blue piece where the poll piece goes.) The white plaster is the piece we just poured in our last step. You can always tell which side got poured first because it has a relatively flat horizon line, whereas the last piece has arcs. This becomes more important later, because plaster molds are designed so that a specific piece gets removed first.

I'll be pouring those blue inner pieces in the next steps. Right now the gusset is one large cavity, but I'll be adding a clay pour hole to preserve that space much like Sarah described in her recent blog post here. (Love the toothpick trick, Sarah!) Many times those inner rubber pieces get cut into smaller pieces, as you can see from the lines separating the front and back gusset into two sections.

The split between these to pieces was made by cutting the rubber after it had cured. If I was going to cast Imp whole, I would be doing this with his gusset pieces, too. Years ago, horses almost always had two gussets - one to the front of the pour hole and one to the back. With ceramic horses getting more and more detailed, multiple gusset pieces are now the norm. The downside to this is that legs often have three mold lines instead of two, which is one reason Imp will be cut apart and cast in pieces. If I put three mold lines on his little legs, there wouldn't be much leg left!

And finally, if anyone has questions don't hesitate to post them in the comments section. I might not be able to give a good answer, because I am still learning. But teaching others (even if you know only a little!) is a great way to learn more, so I will certainly try to answer.

1 comment:

Becky Turner said...

oh ok now I get it! thanks! I am learning so much from this! thanks for doing it.. that was one thing I just never got.. ya know? and now I do!
Rebecca Turner