Wednesday, July 31, 2013

Press Mold Bulbs

One of the potential problems with writing a blog about my process in the studio is that much of my day to day work is pretty repetitive. Yesterday I make almost a dozen pieces, but each one was made using a press mold of the same form. So, basically, this is what I did all day.

I have a couple plaster molds I made years ago to simplify the process of forming these "bulbs."

I pushed a thin layer of clay into both sides of the two-part molds, which are keyed to line up the halves together.

I added a layer of dark slip to the interior of both sides before closing the mold.

I scored and slipped the edges of both pieces of clay before pushing the molds together. Roughing up the edges and adding liquid clay (slip) helps the two pieces of clay to stick together inside the closed mold.

Once the two halves of the mold are together, the porous plaster absorbs some of the moisture from the wet clay, causing the clay pieces to shrink inside the mold and pull away from the wall of the mold slightly.

When the mold is opened up, the "bulb" form should pop out easily.

The seam is visible and needs to be smoothed, but the form is strong and can be decorated and altered. Lather, rinse, repeat.

My goal this summer is to form and fire 100 bulbs to use for a wall installation in a show next year. I've formed roughly a third of the pieces I need to make. I am waiting for most of the pieces to dry and be fired. I have two more in the mold drying right now.

an older iteration of my "bulb" installation


  1. I have just discovered your blog. Great post. But I do have a question: why did you put the dark slip at the inner surface of the bulb?

  2. Thanks Danijela.
    I add the dark slip to the interior because I don't like the look of the naked clay after firing. After the bulbs are formed, I cut some holes in them for hanging. The holes also allow the interior to be visible. I can't easily glaze the interior using the techniques I use for the outside.
    I used to raku fire these forms so the interior was black from smoke. I didn't actually notice or consider the naked clay color until quite recently, so I haven't finished any pieces with the dark slipped interior. I will post again when these pieces are finished.

  3. Do you have a tutorial on how to make the 2 part molds?


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