Pie-Crust Mug-Making Method

This is a method of making mugs that are delicate and functional but impossible-to-mistake for machine-made. Walls are even thickness so they dry well, even when very thin. The method is fast, I can make alot of these. It works with clays of lower plasticity. Every scrap of clay gets used. These are great when I only have a small amount of clay to test. And, most importantly for me, I can integrate 3D printing into the design, form making and cutting operations. While these are hand-made, they can have a consistency of size, shape and weight that make them fit into sets very well.

This is a technique, not to 3D print clay itself, but integrate modern 3D design and 3D-printing to making tools for an age-old processes of forming. Using an inexpensive, off-the-shelf 3D printer and Fusion 360. It is so exciting because of the infinite possibilities it opens. It means being able to make hand-made products at speed and consistency. There are many old-fashioned ways to make complex and consistent shapes, but only a few experts can do them and they are slow. But using this technology even an ordinary potter has the potential do extraordinary pieces.

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3D design for shell mold for cup model

3D rendering in Fusion 360 of the mug body shape

This was created by drawing the outside profile and a simple revolve operation in Fusion 360. And then shelling the shape (from the top) to 0.9mm thickness. I saved it as version 1 (v1). This was early on and I did not do this design parametrically (e.g. the height, top diameter and bottom diameter), I learned to do that later. If I had then each size could have been named height-top-bottom.

Printing the mug model and casting it in plaster

Plaster poured in the mold, the mold split off revealing the plaster part

I 3D printed it using PLA and poured it full of plaster. When the plaster set I peeled the printed shell off. The plaster part is the drape-mold around which the mugs can be formed (according to how the cookie cutter works I will change the size or either this to that). The surface roughness on the plaster was easy to remove using a metal scraper, then sand paper. I normally name 3D prints of this like this: TopDia-BottomDia-Height (making this one 94-66-110). But in this case, I want to maintain the same draft angle (8 degrees), so this is named 66-8-110 (BottomDia-Angle-Height). On first use with my 45-25-108 cutter it was evident that this form is too small. It needs 10mm more of height and 4mm more diameter (so I adjusted it to 70-8-120).

A parametrically-drawn cookie-cutter for slab built mugs

A 3D printed cookie cutter showing parametric measurements, four of these are glued together

You may already know that I am very excited about the potential of 3D printing for creating aids to making pottery. I glue four of these together to create a cookie cutter for producing slab-built mugs. For different sizes of mugs I need cutters with different geometries. This is quarter-cutter and it has been drawn "parametrically" using Fusion 360. That means that certain aspects of its geometry (two lengths and one angle) can be adjusted by simply changing the parameters (in the Parameters dialog). The drawing then adjusts automatically. It is magic! Other aspects are fixed (e.g. the right-angle, the pucker-preventing hole cutouts, the height, and thickness). Parametric design is revolutionary, it fits my try-it-adjust-it-try-it-again way of working. And, I can label these printed quarters according to the size, in this case 45-25-108.

Forming the pie-crust mug

As you can see, it is obvious why I call them "pie crust mugs"! The forming technique is: Roll out the slab. Stretch plastic wrap over it. Press the cookie-cutter down onto it (I press it down with a wooden bat to get even pressure). Remove the extra, place tissues under the wings (so they will fall freely) and invert the plaster form in the center. Flip the board and glue the overlaps using slip and pressure.

Black engobed M340 stoneware with GA6-B Alberta Slip glaze

Hand built. Cone 6 drop-and-hold PLC6DS firing. The engobe is the L3954B base recipe with added Mason 6600 black stain, it was applied at the leather hard stage inside and part way down the outside. The GA6-B glaze enhances the black under it. By Tony Hansen.

Incredible Mother Nature’s porcelain

A hand-built mug made from 100% of a naturally occurring porcelain

This is made from 100% of a natural clay (3B) from the Whitemud formation in Ravenscrag, Saskatchewan. To make this body, which I call MNP, I slake and slurry up the raw clay lumps, sieve it to 200 mesh and then dewater on a plaster table. I rolled the plastic clay into a thin layer, cut it into a cross-shape using a 3D printed cookie-cutter, drape-molded it over a plaster form and then slip-joined the seams. It fires very dense and strong (to zero porosity like glass!). It holds together well and joins well with its own slip. Although not super plastic, it is smooth and fine-grained like a commercial porcelain body. I add 1-2% bentonite to make it more plastic when needed. It can be rolled extremely thin and yet does not warp in the firing! This mug has a weight-to-volume ratio of 2.08 (the weight of water it will hold compared to its own weight).

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Deep blue Mother Nature's porcelain with rutile glaze

By Tony Hansen
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