These are fired at cone 6. The Chinese body was so short that I had to add 3% VeeGum to make it plastic enough to throw thin-walled. However, even with the fluxing action of VeeGum, it is only slightly translucent (even in the bright sunlight). When it comes to whiteness, however, the Chinese porcelain is somewhat better.
Wednesday 5th August 2020
Fired to cone 6 using the C6DHSC schedule. Top: GA6-B. This recipe is 80% Alberta slip and 20% Ferro Frit 3195 (we used to use frit 3134 but have found frit 3195 works much better). Bottom: We added 1, 2, 3 and 4% iron oxide. At about 2%, the color matches the rich reddish effect you would get if you used an 80:20 Albany:3195 recipe (without an iron addition). An added benefit is that the iron acts as a fining agent to remove micro-bubbles to achieve better transparency.
Wednesday 5th August 2020
Louise Solecki Weir working on one of her large sculptures. Sculptors can be passionate about the clay they use. For good reason, they have a lot to lose. While it might seem that Louise would be most concerned about drying shrinkage and drying performance (resistance to drying cracks), not so. To her, the ability to re-wet sections that dry out is paramount. And she has learned to overcome drying challenges posed by the high plasticity to benefit from the smooth texture, workability and rewetability it offers. How plastic is it? It is a five-equal-parts-mix of silica sand/grog, ball clay, Lincoln fireclay, a low fire red clay and a medium fire red clay (there is no feldspar or silica). All four of the clays are highly plastic to super plastic. The body's drying shrinkage would be 8% if it was not for the 20% aggregate (a mix of fine 75 mesh sand with a small complement of fine 40 mesh grog) that reduce it to 6.5%. These offer a far higher surface area than coarse grog and provide channels for water to re-enter. If you would like the recipe of this body (non-production) please contact us.
Wednesday 5th August 2020
The grogs shown here are Molochite 16/30, Christie Minerals STKO 22S and F65 Silica Sand. I wedged 150g of the molochite into 2300g of pugged porcelain (Plainsman M370). This calculates to 7.5% grog (based on 22% water content of the pugged clay). This produced the texture shown. Wedging a grog (or silica sand) into a soft clay body is easy, just sprinkle it on the table and wedge the clay over it. With each push it picks up more, the process is amazingly effective at quickly producing a homogenous material. If the clay is stiff, just moisten the aggregate. Knowing that pugged clays have about 20% water it is easy to calculate a grog addition: A 5 kg slug of clay thus contains 4 kg of powder. To add 10% grog you would add 400g. To add 10% of the total it would be 4000*10/90=444g. How much did this 7.5% grog reduce the drying shrinkage of this body? About 0.5%.
Sunday 2nd August 2020
I had this done at Shapeways.com. They offer an after-print polishing service, which I did not get. The plastic one on the left (actually printed from PLA filament) weighs 5 grams. The steel one weighs 45 grams! It cost $35 to print this. The quality is like regular stainless, this is incredibly hard! Fitting it on the shaft was the first issue. The shaft measures 8mm. My drawing sets the hole at 7.9mm. On the 3D the print with PLA I got 7.8mm, but this this arrived at 7.7mm. It required a lot of work to enlarge the hole to fit. Thus, if I were to print this again, I would set the drawing at 8.2. That should either fit or only require enlarging the hole slightly (using emery cloth). The second issue was the hole and tap for the set screw. Drilling it was very hard, the first bit broke. The second made it through, but we could not tap the threads. So we will glue it to the shaft.
Context: Propeller Mixer
Thursday 30th July 2020
Written by W. C. Worcester. He had a lab equipped with clay processing and testing equipment that many would admire today! He outlines clay geology in general, then the geological history of the province of Saskatchewan in that context. He describes the technology of ceramic materials, the major clays used in industry and the equivalent materials in the province. He submits hundreds of samples with physical test data clearly describing them and their locations (using extensive maps and diagrams). His work inspired Luke Lindoe, who continued it during the 1950s to 1970s. That inspired us to develop the testing methods used at Plainsman Clays to this day.
Tuesday 28th July 2020
Plainsman Clays did 6 weeks of mining in June-July 2018 in Ravenscrag, Saskatchewan. We extracted marine sediment layers of the late Cretaceous period. The center portion of the B layer is so fine that it must have wind-transported (impossibly smooth, like a body that is pure terra sigillata)! The feldspar and silica are built-in, producing the glassiest surface I have ever seen at cone 6 (2200F). Despite this, pieces are not warping in the firings! I have not glazed the outside of this mug for demo purposes. I got away with it this time because the Ravenscrag clear glaze is very compatible (similar thermal expansion). But with other less compatible glazes they cracked when I poured in hot coffee. This mug was the beginning of an exciting project the sieve out +325 mesh particles any make many more pieces.
Friday 24th July 2020
Nepheline Syenite is a type of feldspar. We use it in porcelain bodies. The nepheline content determines the temperature at which the body is vitreous. We use this product in preference, where possible over soda or potash feldspar. There are several reasons: It is mined and processed in Canada and is renowned around the world for it's quality. If has a very low iron content, this makes for whiter-burning bodies. It is a more powerful flux than common feldspars. It has been very consistent over many decades.
Wednesday 22nd July 2020
These tiles are a 50:50 mix of Plainsman L215 and M390. They are fired at cone 1, 2.5 &4 (columns 1,2,3). The glaze is G3806N (v1) with stains at 10% concentrations. That glaze is a fluid-melt for cone 6, but it performs nicely down to cone 1 and even lower. There is no visible crazing and the iron body is stoneware-strength. The firings were only held for 10 minutes at cone (no slow cool). These coloured glazes are also less "muddied" by the iron in the body than would be the case at cone 6. This is a really amazing result. Red-burning bodies can be difficult at cone 6 (if fired too high the red color is lost, if fired too low they are too porous). If you do not have the frit for the N version, try G3806E or G3806F.
Monday 13th July 2020
This is what you need to be independent, to create your own manufacturing company in your garage. Some of the prices are "instead of" rather than additive. There are many approaches to glazes, the more you are willing to learn the better you will be able to make your own (and save a lot). We recommend the cone 6 range using a small test kiln (like this 220v ConeArt GX119, don't scrimp on this, go for quality and the practicality of a Genesis controller). A kiln you can fire often and inexpensively is a key enabler to learning, developing techniques, products, designs, durable and decorative surfaces, solving problems. It can be fired multiple times a day. And it is big enough for mugs and similar sizes. It will get you into the habit of using some of your creativity for experimenting. It will give you the successes early on that will inspire you to press on learning. When you are ready, then get a big kiln and hit-the-ground-running. This potter's wheel is the best available and will last a lifetime, these often appreciate in value over time. And, build yourself a good plaster table. You will use it constantly. Not shown here is a propeller mixer, also an important tool. And you will need a sink equipped with a sink trap (Gleco Trap).
Monday 6th July 2020
Find thousands more like the following: Use the search field at the top of the page at the Digitalfire Reference Library.