This GA6-B glaze is better than beer bottle glass

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.

Related Pictures

3D-printing artifacts under an amber glaze on light and dark bodies

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 color difference is entirely a product of the difference in color of the fired clay body. The wood-grain texture is the artifact of 3D-printing the case mold flat rather than upright.

Regular bottles of beer looking very humble beside the ceramic one

Ceramic beer bottle in a case with glass ones

This is v2 ceramic beer bottle in a common-sized 6-pack case. Of course, our case will have our logo and artwork. I paid $19 for it. They threw in the bottles of beer for free! That is a ceramic bottle that has bumped out the ordinary glass one and is showing off its size and superior character. But it is a tight fit in this case - it appears to be 4mm too large in diameter. I am sworn not to have another beer until it is served in a proper ceramic bottle like this. So if you live in my home town and want those six unneeded bottles, let me know.

Meet two glazes at the rim using wax emulsion. Why? How?

Reactive glazes (melt-mobile, crystallizing or heavily pigmented) are the least suitable for food surfaces because they have the potential to leach metals. Liner glazing ware is an excellent way to deal with this problem. Not only does this approach improve functionality but it can be aesthetically pleasing and practical in production. This liner is GA6-B, a pottery glaze recipe we promote with confidence. Not only is it less likely to be leaching metals but also less likely to craze - this assures water tightness on non-vitreous bodies and eliminates any potential for bacteria growth in the cracks (especially if the body has porosity). Unfortunately, glazes that leach are also likely to stain and cutlery mark - these add more reasons why they are most often unsuitable for food surfaces. The straightness of the dividing line is affected by both the application technique and the degree to which the two glazes bleed into each other and run. Read and watch our liner glazing step-by-step and liner glazing video for details on how to do this - it is practical for any potter or hobbyist (or even in production). And tap/click the picture above for other examples of this.

Links

Glossary	Food Safe Be skeptical of claims of food safety from potters who cannot explain or demonstrate why. Investigate the basis of manufacturer claims and labelling and the actual use to which their products are put.
Projects	Beer Bottle Master Mold via 3D Printing A project that took several years of failures and blind allies and is finally coming together - so much simpler than expected!

Got a Question?

Buy me a coffee and we can talk