Thursday, September 6, 2007

Still more moldmaking

I thought it might be helpful to post a few more moldmaking pictures. In previous posts, I showed some of the rubber production molds. Those are used to make the plaster molds needed for slipcasting. They are "molds to make molds". This time I will only need one mold, so I am skipping that step and making a plaster mold from the start.

What I want to do is take the tile that I have been working on in Chavant clay, and create a duplicate in greenware. My reason for doing this is two-fold. First I am not sure how I want to finish the piece, so multiple copies will give me the option to work on a number of variations before I settle on a favorite. The other reason is that I prefer working in the greenware during the detailing stage. There is something to be said for being able to smooth out rough spots with a damp brush!

So this is the tile, the first of a planned series on the seasons.



He was sculpted in Chavant clays on top of an old piece of shelving. I use a variety of clays to get the level of firmness I need. As you can see, sometimes that means more than one color of clay! He still needs work (and a mane!), but at this point the basic shapes are where I want them, and I'm ready to pour plaster.

He's not suited to a simple mold, though. The outside edge of his muzzle creates an undercut. If I poured plaster over him now, when I tried to pull the tile I would end up ripping his nose off! So I need to make an inset piece that will come off first. For plaster moldmaking, though, what comes off first gets poured last. We need to fill that area with clay, then, so that a gap remains for the later piece.



You can see some residue from the blue plasticine I used to create the inset piece. (I enhanced it in Photoshop with a dotted line.) Unfortunately, these pictures were taken after the waste mold was made, but here is a more complicated mold with the pieces filled in this way.



(This one was done by my mentor, Joan Berkwitz of Pour Horse. That's why it's neater than mine!)

At this point the tile was boxed up much like the horse above, and the plaster was poured. Once that set and everything was cooled, I banded the shelving and the plaster together and carefully removed the blue clay. That's why I make my pieces out of blue clay - so I can tell where it ends and my original starts! Once the clay is out, I seal the exposed plaster with mold soap and pour the insert.



Next the shelving was pulled off the back (luckily leaving the tile imbedded in the plaster), the exposed plaster is sealed, and the whole thing boxed up once again. Then the lid - our third piece - is poured.

This is the finished mold without the lid.


Here it is with the insert in place, and the lid beside it.



Now I have a waste mold. In my next post I'll explain what I do with it!

5 comments:

Carol H. said...

Thank you for posting these pictures and information about the moldmaking process, it's really fascinating and your simple explanations and pictures really help!

DeeAnn said...

Loved reading about how you create your molds, and the photos are great. Thanks for posting this info!

Hyn said...

Yep, making a mold before you are finished, and continuing the work with greenware casts is exactly what I have been doing with my draft sculpture. I too find it much easier to work with the raw, unfired greenware than yucky oil clay! I am glad that I am not alone in that insanity. :}

Very lovely blog, Lesli. Keep up the fantastic and informative posts. I figured out how to subscribe (your adding FeedBurner made it MUCH easier now, thank you!) and now I just need to get off my butt and add more to my own blog.

Paige Easley Patty
Hanblechia Studio

Lesli Kathman said...

Not only is working in the greenware easier (to me, at least), but I think of it as being the sculpting equivalent of the computer's "Save" command. Once I have that waste mold, I know I can't really lose the work up to that point!

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