3D-printing artifacts on a slip cast M370C bottle. A problem?

Here is why the stair-casing artifacts are not the problem many people think. These are stonewares fired at cone 6 oxidation. The dark one is M370C with 10% added raw umber. The other is M370C. Both are glazed using GA6-B Alberta Slip amber transparent. The wood-grain texture on the right is an artifact of 3D-printing - the case mold was printed flat rather than upright. Strangely, that is the bottle people want! But the production prototype bottle is the one on the left and the stair casing is barely visible. Additionally, these are prototypes, the production molds would either be made by printing the model upright or by casting a plaster model of a bottle half, smoothing and soaping it, attaching it to a clamping baseplate and then setting up 3D printed railing around it.

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3D printing artifacts on a bowl model. Are these a problem?

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3D printing is resetting and revolutionizing all fabrication industries. It has taken hold because it brings exciting new capabilities we never had before, especially in ceramics. Each disadvantage is being addressed and solved. This stair-casing, or more correctly, "printing artifacts", are often cited as a reason not to adopt 3D. But these are not an issue here. First, most of the surface on this case mold is not exposed on the final piece. Second, near vertical and fully horizontal printed surfaces, such as the shell around the outside and the spacer ring, don't have artifacts. Third, this bowl model is not 3D printed, it is plaster that was poured into a 3D printed shell. Before use, this will be stuck down onto a potter's wheel and tooled smooth. It is then attached to a clamping baseplate and the 3D printed railing clamped around it.

This GA6-B glaze is better than beer bottle glass

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Ceramic glazes are actually just glass. But they are not like bottle glass. The latter is formulated to work well in forming machines (harden quickly), melt and stiffen quickly, have low melt viscosity and resist milkiness and crystallization on solidification. The chemistries to accomplish this have adequate resistance to leaching and adequate durability for a single or few uses. A stoneware glaze melt needs to be much more viscous (to stay put on vertical surfaces). And, it must have a much lower thermal expansion (to match common clay bodies). And, it must resist crystallization more much (since it cools slowly). Fortunately, meeting these needs brings along big benefits: Greater durability, hardness and resistance to leaching. Common target formulas express typical oxide formulas of glazes. Stoneware glazes and bottle glass share a common trait: They have about the same amount of SiO₂. But the similarity ends there, stoneware glazes have:

-High Al₂O₃. Three to five times more! It is the key oxide to producing durable glass. And it stiffens the melt (that disqualifies high levels from bottle glass).
-The same fluxes (CaO, MgO, K₂O, Na₂O). But they distribute very differently (half the CaO, half to one third the KNaO, much more MgO). Other fluxes like SrO, Li₂O are also common.
-Low KNaO (which they call R2O). In glazes it produces crazing, 5% is a typical maximum. But bottle glass can have double or triple that (the high thermal expansion is not an issue and its cheap source materials supply lots of melting power).
-B₂O₃ melter. It is expensive but can be justified because the glaze is just a thin layer. Glazes at the low end of the stoneware range have 5% or more boron.

The ceramic bottles shown here are made from a dark burning stoneware, the glaze is GA6-B. On the left is the same glaze on a porcelain mug. For the above reasons this glaze is more durable and leach resistant that regular bottle glass.

Links

Recipes	GA6-B - Alberta Slip Cone 6 transparent honey glaze An amber-colored glaze that produces a clean, micro-bubble-free transparent glass at cone 5-6. Works well on brown and red burning stonewares.
Typecodes	3D printing problems 3D design and printing for mold making in ceramics bring exciting new capabilities. Awareness of the issues and knowing how to mitigate each is a must. 3D is resetting all fabrication industries and engineers are solving every problem, you can too.

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