Dark Umber-Stained Engobes on M340 at cone 6
This is the standard Plainsman L3954D white engobe
recipe with the 10% Zircopax switched for Burnt Umber. The result is a dark, rich, ultra-gloss brown (almost black). The engobe
is applied inside and half-way down the outside. The mug on the left is glazed inside and out with the base GA6A Alberta Slip cone 6 recipe (but uses Ferro Frit
3195 instead of 3134). The one on the right has the same glaze on the outside but the G2926B
clear transparent on the inside (it is micro-bubbling). This engobe works even better with a black stain.
Context: L3954B - White Cone 6 Engobe for Plainsman M390, M340, GA6-A - Alberta Slip Cone 6 Amber Base Glaze
Monday 2nd October 2017
Deep, deep blue without any cobalt. How?
These have to be seen to be believed, it is the deepest, richest blue we have ever produced. This is Plainsman M340 fired to cone 6. Black-firing L3954B engobe
(having 10% Burnt (not raw) Umber instead of the normal 10% Zircopax) was applied inside and partway down the outsides (at the stiff leather hard stage). The incising was done after the engobe
dried enough to be able to handle the piece. The glaze is Alberta Slip rutile blue. Firing schedule: Cone 6 drop-and-soak
Context: GA6-C - Alberta Slip Rutile Blue Cone 6, Cone 6 Drop-and-Soak Firing Schedule
Wednesday 20th September 2017
Vintage boxes of Plainsman Clay found. From 1966!
M20 was for forerunner of M340. M22. We are not actually sure. Does anyone know? Would it still be good? Definitely. Just smash it up and put the dried pieces in a bucket of water to slake.
Tuesday 12th September 2017
Kiln wash that really works. How?
The shelf on the right in the traditional kaolin:silica kiln wash. Flaking constantly. Sticking on the feet of ware. A real aggravation. The one on the left: perfectly even. Yet thin. Much more refractory
so it has not hardened or become brittle. Or cracked. And it paints on beautifully. The secret? Zircon. Zircopax, to be precise. Zircopax is among the most refractory
materials in ceramics. We mixed it with some calcine
d, rather than raw kaolin. That greatly reduces drying and firing shrinkage and helps densify and stabilize the coverage (by its flat particle shape). Laguna gum solution was added to harden the dry layer and slow down the drying (their gum solution has a higher percentage of CMC than achievable using common mixing methods). Click the link below to get the recipe.
Context: Plainsman Super Kiln Wash, Kiln Wash
Thursday 7th September 2017
Common dipping glazes converted to jars of brushing glazes
These are cone 6 Alberta Slip recipes that have been brushed onto the outsides of these mugs (three coats). Recipes are GA6C Rutile Blue on the outside of the left mug, GA6F Alberta Slip Oatmeal on the outside of the center mug and GA6F Oatmeal over G2926B
black on the outside of the right mug). One-pint jars were made using 500g of glaze powder, 75g of Laguna CMC gum solution (equivalent to 1 gram gum per 100 glaze powder) and 280g of water. Using a good mixer you can produce a silky smooth slurry of 1.6 specific gravity
, it works just like the commercial bottled glazes. The presence of the gum makes it unnecessary to calcine
the Alberta Slip.
Context: CMC Gum, Where Do I Start?, Brush-on commercial pottery glazes are perfect? Not quite!, Glaze Layering, Brushing Glazes
Thursday 7th September 2017
Polymer plates. Great for stamping into clay.
These are samples made by Boxcar Press. They make different depths, you need the 0.047 relief depth. While the others will press a crisp design into the clay, the shallow depth will make it difficult to avoid rubbing out the color from the recesses when you a sponging it off the top. Traditionally polymer plates have had metal backing and were expensive, but these are plastic and inexpensive. When designing them create a border around the outside of the design to contain it. This is needed because when the stamp is pressed hard into the clay, it smears away from all outer edges of the design, that containment-line keeps those edges clean. Also, they do not actually need to be stuck to a piece of wood, it is often better to lay them face down on the clay and use a wooden block and hammer to press them in to stiff clay. Use spray cooking oil as a parting agent if needed. They are flexible and peel off easily.
Context: Example of a logo done using a polymer plate
Thursday 17th August 2017
How to make a ceramic time-bomb
This mug is pinging loudly and literally self-destructing in front of my eyes! Why? The glaze is under so much compression (the inside is pushing outward, the outside inward). Spiral cracks are developing all the way up the side. Small razor-sharp flakes are shivering
off convex contours. Why? I accidentally fired a low-temperate talc body at cone 6 (the glaze is the Alberta Slip base cone 6 glossy). The clay body is not overly mature
, but it just has an extremely high thermal expansion
(talc is added to increase the expansion to fit low fire commercial glazes, they would craze
without it). Shivering
is serious, it is a mismatch of thermal expansion
between body and glaze. It can happen at any temperature.
Context: Shivering, Glaze fit, Glaze Shivering, Glaze Crazing
Tuesday 15th August 2017
A bubbling glaze having an encapsulated stain fixed. How?
These two pieces are fired at cone 6. The base transparent glaze is the same (G2926B
Plainsman transparent). The amount of encapsulated red stain is the same (11% Mason 6021 Dark Red). But two things are different. Number 1: 2% zircon has been added to the upper glaze. The stain manufacturers recommend this, saying that it makes for brighter color. However that is not what we see here. What we do see is the particles of unmelting zircon are acting as seed and collection points for the bubbles
(the larger ones produced are escaping). Number 2: The firing schedule. The top one has been fired to approach cone 6 and 100F/hr, held for five minutes at 2200F (cone 6 as verified in our kiln by cones), dropped quickly to 2100F and held for 30 minutes.
Context: G2926B - Cone 6 Whiteware/Porcelain Transparent Base Glaze, Firing Schedule, Encapsulated Stains, Cone 6 Drop-and-Soak Firing Schedule
Tuesday 8th August 2017
Eighteen Plainsman M390 mugs from half a box of clay!
Boxes are 20kg (22.68 lbs). Plus there are enough trimmings to make about two more. That is about 500g of pugged clay per mug. These have been trimmed and engobe
d (using our standard cone 6 engobe
) and are drying. Notice I have waxed the outers of some of the handles to slow their drying down (to keep it in sync with the mug itself). M390 is likely the most plastic native Plainsman body. Although it was not overly soft I stiffened up the clay for ten minutes on a plaster bat to make it my ideal throwing stiffness.
Context: Plainsman M390, Plasticity
Saturday 8th July 2017