An 85-year-old Medalta Thrown Beer Bottle:

How can it be so white, speck-free and uncrazed?

These (right) were made individually in the factory during the 1930s and 1940s (the insides have pronounced throwing rings and slip drips). The potters were able to make up to 500 per day, even though they took the time to smooth the outside using a rib! The inside base of this one is bowl-shaped (the walls near the base are very thick), this helps explain how they were able to throw them so quickly.

Perhaps most surprising is how much whiter and speck-free the bottle is even though it is fired four cones higher than the crock (Plainsman M340 at cone 6). Both pieces have porosities above 2%. Why? First, they got their clay from further east in Saskatchewan (near Willows), where the cleanest clays are much lower in iron contamination (likely the H0009 body). The whiteness is better even though they would have had to add some ball clay to make the clays more wheel-throwable. Second, they employed a wet process to refine the clay (slaking, blunging, sieving and filter pressing), this enabled them to sieve out the iron pyrite particles. Fortunately, modern dry grinding and air separation equipment is greener and able to accomplish without water.

Notice also the transparent G1129 glaze on the beer bottle (the upper section is likely the same glaze stained using iron oxide): After almost 100 years it has not crazed. This is both a testament to the ease of glaze fit these natural materials offer (because of the high quartz content) and the skill of the engineers of the time at matching the thermal expansion of glaze and body.

Related Pictures

Classic Medalta Potteries Beer Bottle Mold

Making a new mold using 3D printing

Medalta classic beer bottle mold for slip casting

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The original bottles were hand thrown and very heavy. This one, for example, weighs 525g. Our bigger slip cast equivalent with a modern shape, 3mm thick walls and much higher capacity weighs only 400g.

The color, enduring glaze fit and the type of clay used by Medalta indicates these were likely fired at least to cone 10. Energy was cheap at the time and the Saskatchewan clays they used require high firing.

This is a test mold to determine if the swing top stopper will work on a neck of this shape. This mold only weighs 87g and the walls are printed to only 0.8mm thickness. Two natches are sufficient to keep the halves aligned perfectly. Pieces will shrink about 12%, thus the larger size. We will use tissue transfers for the decorations, the GA6-B glaze for the inside and shoulder and G2926B transparent for the body.

New incentive to develop Canadian clays:

Reduce the “clay miles”.

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The materials to make M340 travel 200km to get to our plant (from Ravenscrag, SK).
M370 is a different story. The kaolin (from Georgia) travels 3700km, the nepheline (from Ontario) travels 3100km, the silica (from Illinois) travels 2300km, the ball clay (from Tennessee) travels 2800km and the bentonite (from Wyoming) travels 1000km. Weighting each material distance by its percentage in the recipe calculates to 2900 clay-kilometres! Thus, all the boxes of M370 we make in a year travel about 60,000,000 km, enough to go to the moon and back 50+ times! This realization brings renewed motivation to develop new clay deposits, ones that are white enough to make an M370-like body and which are only 400km away. Until then, you can cut the mileage now: Use an engobe on M340 and make it whiter than M370 (and darker than Coffee clay).

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