Molds for hand-built hexagonal clay vases

These molds are inspired by @KatzCreates excellent work on creating 3D-printed tooling for pottery. Specifically, this video on mold making.

The basic shape is a hexagonal vase in two different sizes, a larger 4" tall model and a shorter 2.5". The shorter size also provides optional angled bottom faces, allowing the finished piece to sit at an angle in addition to straight up and down.

Using the molds

To mold a full vase, you will need three top and three bottom molds in your desired side. Any combination of bottom pieces will work for the bottom molds. Mine are printed in PLA with ~15% infill. I used tree supports, but they only actually touch the keys / keyholes on the molds, so they may not be required. I didn't do any specific post-processing to remove layer lines, since that can be cleaned up later.

Note: clay shrinks as it dries and is fired! All of these molds are actual-size, so you'll want to scale them up in your slicer to account for shrinkage. If you forget, you'll still have functional pieces, they'll just be smaller than you might expect.

You'll want mold release of some kind. I've found corn starch works well. Give the insides of the mold pieces a good dusting and rub it around a bit to make sure you have good coverage.

Once you've got a set of molds prepared, it's time for clay! You'll need a normal assortment of hand-building tools. I happen to be using a dark stoneware clay in the photos, but other clay types could be fine. Roll the clay into a slab (I typically aim for 5-7mm thick) and cut pieces a bit bigger than the mold pieces. Then, gently press the clay onto the molds and trim to fit (photo 2 in the examples). Slip and score the edges, and assemble the bottom and tops of the mold, smoothing the seams you can reach (photo 3). I use rubber bands for the small molds, and masking tape for the large ones, just to hold pieces together. Then, repeat connecting the top and bottom sections. (photo 4).

From there, wait a bit for the clay to dry and gently start to demold (photo 5). I've found it to be best to try to remove one vertical wedge at a time. Plastic doesn't draw away moisture the way plaster would, so you will likely need to be patient or carefully apply a heat gun to get the clay to release. You'll likely have visible joins on the clay  (and layer lines) so smooth them out with your rib of choice. Proceed as you would from here.

Bonus use: hex bowls

You can use the bottom parts of the molds to make hexagonal bowls. Just skip making the top half. I find the 4" size is pretty good for snacks. The smaller size are adorable, and could be handy for mise en place or small paints.

Extra bonus: positives included

I've included the positive shapes I used to make the molds. They're solids, but they print pretty well in vase mold, and you can readily cut them up to e.g. make hump molds.

Clay details

The clay in the example photos is from Georgies. The dark is Trail Mix Dark Chocolate, and the light (used in the marbled clay and as the base for the blue/green vase) is Kristy Lombard.

All of the glazes are from Amaco. The blue/green large vase has cobalt (bottom) or snow (top) under seaweed. 3 brushed coats of each. The small vase has 1 layer of snow brushed on and sponged off over three brushed layers of rainforest. The large, marbled vase is bare clay.