|Monthly Tech-Tip |
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.
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.
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).
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 my 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 changed 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, 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 parameters, in this case 45-25-108.
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.
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.
Each of these fired fragments is made from a mix of 65 ball clay and 35 nepheline syenite. These are the remnants of a DFAC test done on each (soluble salts concentrate on the outside edge of a disk as it is dried with the inside protected). Clockwise: Spinks Blend, 54S, OM4, M23, Gleason and KT1-4. Each of these ball clays produced a zero-porosity dense fired ivory porcelain at cone 6, they all have remarkably similar appearance. And they all have a high level of soluble salts.
This is made from 100% of a natural clay (3B) from the Whitemud formation in Ravenscrag, Saskatchewan. I rolled the plastic clay into a thin layer, cut it into a cross-shape, 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 has the ability to 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).
Slab-built using my 'pie crust' technique. Cone 6 C6DHSC slow-cool firing schedule. The glaze is GA6-C Alberta Slip rutile blue. The raw porcelain surface exhibits a stunning deep-blue color (although not visible since this piece is glazed). However the blue does bleed up into covering glazes, making them more vibrant. And it highlight contours since the thinner glaze layer shows more of the underlying blue. Mug by By Tony Hansen