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Here is how M340 should behave

You should be able to bend it and stretch it like you see here without any issues. If you are having problems, then please tell us how your experience is different than what you see here.

Friday 22nd February 2019

Making your own ceramic rutile

Making your own ceramic rutile

Left: GA6-C rutile blue glaze on a brown stoneware. The 4% ceramic rutile powder gives the blue variegated effect. Right: We ball-milled our granular rutile and then screened it down to 325 mesh and put that into the same glaze. The results are the same. So if any of your rutile glazes ever lose this effect with a new supply of the material the cause could be that it has not been milled sufficiently fine. Finer rutile powders are browner in color.

Friday 22nd February 2019

Three visual glaze mechanisms make this piece unique

Three visual glaze mechanisms make this piece unique

"Mechanisms" are specifics about the glaze application or preparation process, the materials, the chemistry or firing schedule that produce a specific visual effect. This is fired at cone 10R. It is made from a buff stoneware, Plainsman H550, and has L3954N black engobe on the inside and part way down the outside. The transparent glaze on the inside gives the black a deep vibrant effect. The outside glaze is G2571A with 3.5% rutile and 10% zircopax added (the latter imparts opacity and the former produces the variegated surface). The powerful color of the black engobe wants to get through but it is only able to do so where the glaze layer is thinner (producing the varied shades of brown with differing thicknesses of glaze that occur because of the presence of the incised design).

Saturday 16th February 2019

More problems measuring glaze specific gravity using a hydrometer

More problems measuring glaze specific gravity using a hydrometer

First, the hydrometer is long, the only container I have is this graduated cylinder. I had to fill it just the right level so it reads near the top. OK, fine. But the hydrometer needs to bob up and down to find home. However this glaze has a creamy consistency, that prevents free movement. OK, I will carefully help it find home by pushing it down a little. But then it doesn’t want to bob back up! Ok, I’ll pull it up and push it down and put it where I think it should float. Not great. Next problem: The glaze is opaque, I can’t see the reading. Yikes! A better way would be to throw out the hydrometer and just tare the empty cylinder on a scale, fill it to 100 and read the SG as the weight/100. If this glaze was free-flowing and watery it would be a different story, the hydrometer would be useable.

Tuesday 12th February 2019

Do ceramic material powders go bad?

Do ceramic material powders go bad?

Many minerals are just ground up rocks, they were in the ground for millions of years (e.g. kaolin, feldspars, ball clays, bentonite, calcium carbonate, dolomite, talc, kyanite, wollastonite, etc), so the powders should last millions of years as well. Some are powderized man-made glasses and sintered solids, these are very stable (e.g. frits, stains). Other man-made materials are less stable and can hydrate or oxidize (e.g. carbonate colors, plaster), keep them sealed containers. Some materials are organic (e.g. Gum Arabic) and they can go bad in damp conditions, so keep them in a sealed container also.

Wednesday 6th February 2019

Cracking casseroles. Why?

Cracking casseroles. Why?

The cracks happened on heat up (since they have opened up wide). A combination of issues contribute. The kiln shelves heat-sink the wide flat bottoms, vessel walls are thick, there is some unevenness of wall thickness and only a 30-minute hold at 220F to remove glaze water from the bisque (that could have left dampness in thicker sections); these combined to produce temperature gradients within the piece. The firing schedule rose rapidly from 250-2100F (400F/hr) amplifying these gradients as it climbed. At quartz inversion these gradients produced a wave of volumetric change moving through the bisqued piece and it initiated a crack where different thickness met at a sharp contour, the bottom corner.

Monday 4th February 2019

Vitrification can be obvious by simple visual inspection

Vitrification can be obvious by simple visual inspection

The unglazed surface of the left piece has a sheen, it is a product of glass development during firing to cone 6. That body is a 50:50 mix of a cone 8 stoneware and a low fire earthenware red (a material that would normally be melted by this temperature). Together they produce this dense, almost zero-porosity ceramic. The unglazed surface on the right looks more like plaster, and it is absorbent, about 5% porosity. It is a mix of the same stoneware but with 50% ball clay. The refractory ball clay assures that the stoneware, which was already inadequately vitreous, is even more so. As you can imagine, the left piece is far stronger.

Monday 4th February 2019

200 Shimpo wheels just arrived, ready to be certified

200 Shimpo wheels just arrived, ready to be certified

January 2019. Another shipment of wheels and pugmills from Nidec-Shimpo. Although a large company, making drive mechanisms for many types of heavy equipment, they apply their technology to potter's wheels as a matter of pride in a country that reveres pottery in its culture. Every box has been opened to reveal the existing serial number. A certified inspector will check every one of them and affix another sticker to assure they meet CSA Code SPE-1000 for electrical safety. This approval enables the sale of the equipment to public institutions. And it assures your that the equipment meets CSA electrical standards and is safe to use.

Tuesday 22nd January 2019

Liquify of a pint of brushing glaze. It's easy!

Liquify of a pint of brushing glaze. It's easy!

I counter-balanced the measuring cup and weighed out 250g of water. Then I added 100g of Laguna gum solution and stirred it. I put that into the blender and added 500g of powdered glaze (you can use any glaze recipe). I started the blender on slow then increased it one-at-a-time to full speed. After less than a minute (and a little work with a spatula) it was creamy smooth. It painted evenly on the tile just like a commercial bottled glaze, drying slowly. This produces a specific gravity of 1.58 (which is pretty high) so I can add water and thin it with no issues.

Thursday 6th December 2018

G2934Y glaze with stains on P300 and Polar Ice

G2934Y glaze with stains on P300 and Polar Ice

Mugs hand-built by Tony Hansen. This base glaze is an adjustment to the original G2934 matte. It employs a frit to source the MgO instead of dolomite. The result is a glaze that melts and flows very well, yet is matte. And it is a great host for a wide range of stains, they look better in this than in a glossy base. The only color that has not worked well so far is purple.

Thursday 6th December 2018

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