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Published Feb 14, 2024

I have to admit, I have been guilty of getting a little careless in my throwing and accidentally making a bottom of a pot too thin. If you can relate, this article is for you!

In today's post, an excerpt from the Pottery Making Illustrated archive, Stephen Phillips demonstrates how to seamlessly fix this common problem with a thrown slab. - Jennifer Poellot Harnetty, editor

Have you ever thrown a lovely form to only find later that you have thrown the bottom too thin? If so, you know the feeling of being both frustrated and left with thoughts on how to fix it. Of course, the disciplined thing to do is to check the bottom with a needle tool before the first pull. But, in case you have forgotten to do so, here is a way to fix the base using a slab and a Giffin Grip.

Taking Measurements

There are a few ways to measure the base of your form. I usually use pottery calipers to ensure that the measurements are accurate. Flip the piece over and use the calipers to measure the diameter of the base (1). Make sure you are measuring from edge to edge of the base. Once you have the measurements, lock the calipers in place.

1 Measure the base of the freshly thrown pot with calipers.2 Cut the thrown slab to the caliper measurements using a needle tool 3 Trim and remove the too-thin bottom from the pot.4 Compress the bottom of the pot with a flexible rib to secure the attachment.


Throwing and Measuring the Base Slab

Once you have the diameter measurements, fixing the base of a pot can be simply done by rolling out a slab of clay or throwing a slab on the wheel. For the jar shown here, I threw a slab using ¼ pound of clay. Throw the slab about ¼ of an inch thick. After the slab is thrown, with the wheel spinning, hold the calipers over the center of the slab with one hand (the hand opposite of your writing hand). With the other hand, use a needle tool to cut the slab to the exact size by aligning the needle tool right at the edge of the calipers (2). Cut all the way through the slab to the bat. Cut away the excess and clean up the edges. Use a heat gun to dry out the slab a little. This process makes the slab easier to pick up off the bat, and it also helps to bring the slab to a drying stage similar to that of the form. With a wire cutter tool or fishing line (my preference), cut underneath the slab in preparation for removal.

5 With the wheel moving, trim the excess clay from the bottom edge of the pot.6 Place the jar back upright, place the lid on, and allow it to dry slowly.


Giffin Grip It

Use your Giffin Grip to center the piece with the base up and accessible for trimming. With your needle tool, trim away the thin base to remove it. Trim as close to the interior wall of the form at the base as possible (3). Now, slip and score the base of the form and the edges of the slab where you will attach the two. Attach the slab to the base and apply pressure to the attached area to ensure that the two pieces are joined. Use a small rubber rib to help smooth out the base and to compress the bottom (4). As this is done, the clay will expand a little beyond the edges of the pot. That is perfectly fine. Trim the edges and the excess clay off the base (5). Finally, use a trimming tool to refine and smooth out the base.

After you are done, stand the piece upright (6). Allow it to dry slowly by covering it lightly with plastic. Bisque fire the piece once it is fully dry, and then glaze it up!OL_finished-jar-SPhillips

Stephen Phillips is a ceramic artist from Crawford, Mississippi. He earned a BFA in ceramics from Mississippi University for Women. In 2015, he established Stephen’s Potter House Productions, a small studio space in the countryside of his hometown. Since college, he has had solo and collaborative exhibitions. See more on Facebook: Stephen’s Potter House Productions, Instagram: @sphouseproductions , and Etsy at

**First published in 2021.