Wanna throw porcelain plates with thick bottoms and thin rims?
Then they may need a week to dry! This plate had a one-inch-thick base (while the rim is a quarter of that). During the first few hours a thin rim like this will dry quickly, leaving the base far behind. But as soon as it would support the weight of a cover-cloth I put it into a garbage bag and sealed and left it for several days. Even after that it did not detach easily, even though the bat had been dry. The base was still quite soft but the rim was stiff enough to enable turning it over and trimming it (I endeavoured to create a cross section of even thickness). Then I dried it under layers of cloth for several more days. It took at least a week. Had I allowed the rim to dry out during the first few hours it would likely have cracked later on.
Context: The Black Art of Drying Ceramics Without Cracks, Drying Performance, Body Cracking During Drying
Tuesday 9th April 2019
Supercharge the plasticity of cone 6 reclaimed clay
If your reclaim is short and non-plastic you can make it better-than-new by using an additive of 50% ball clay and 50% bentonite. While only a few percent bentonite supercharges the plasticity
of any clay body it is almost impossible to get it to mix into a wet slurry or plastic clay. But thoroughly shaking it together with ball clay (in a plastic bag) separates the super-tiny particles of bentonite between the almost-as-tiny particles of ball clay, that new powder will easily mix with water. And it fires to a tan-buff stoneware at cone 6 so it won't change the fired appearance of most buff or brown cone 6 stoneware bodies.
Tuesday 9th April 2019
GA6A Alberta Slip base using Frit 3124, 3249 and 3195 on dark body
The body is dark brown burning Plainsman M390
(cone 6). The amber colored glaze is 80% Alberta Slip (raw:calcine
mix) with 20% of each frit
. The white engobe
on the inside of two of the mugs is L3954A (those mugs are glazed inside using transparent G2926B
). The Alberta Slip amber gloss glaze produces an ultra-gloss surface of high quality on mugs 2 and 3 (Frit
3249 and 3195). On the outside we see it this glaze on the white slip until midway down, then on the bare red clay. The amber glaze on the first mug (with Frit 3124) has a pebbly surface. These are fired using a drop-and-soak
firing schedule. Some caution is required with the 3249 version, it has low thermal expansion
(that is good on bodies that normally craze
glazes, but risks shivering
on ones that do not).
Context: Ferro Frit 3249, GA6-A - Alberta Slip Cone 6 Amber Base Glaze, GA6A Alberta Slip base using Frit 3249 and 3195 on buff body, P300 and M370 mugs with GA6A Alberta Slip (using Frit 3249), Alberta Slip Cone 6 Base with Frit 3249, 3195, Plainsman Cone 6 Slow Cool (Reactive glazes)
Monday 8th April 2019
Functional ware at low fire! Don't dismiss it just yet.
These were only fired at cone 04, but they are durable enough to last some time with normal use. The insides have a transparent glaze (Spectrum 700), it is leadless and completely safe. These are great insulators, they keep coffee warm longer than porcelain or stoneware. The feet are glazed so they are fine for the dish washer. They are super-light, the body is made from ball clay and talc and throws really well. These shrink very little on drying (in this case less than 2% compared to porcelains which can be 8% or more). These are inexpensive to fire, only four hours to cone 04. They withstand impacts better than you think (a thin porcelain mug propagates cracks and can shatter). Colour, glorious color! These are Spectrum Opaque low fire glazes, dozens of wild colors are available.
Context: Which is better for functional ware? Cone 04? Cone 10 reduction?
Monday 18th March 2019
Cheap Amazon glaze mixer, how does it stack up?
Make some adjustments and it is usable. First, it is very quiet and has lots of power. The plastic sliders ride smoothly and provide precise adjustability (but the plastic threads might not last). The vertical shaft is stainless steel and the cast iron base is heavy, sturdy, practical. The motor-to-shaft mounting collar is good quality (but must be tightened with a tool). It has a stepper motor that runs less than 300 rpm (not the 3000 advertised)! The timer switch will not likely last, better to leave it on and use on/off. It does not turn off completely on zero-speed setting. The propeller shaft is too short and the flapper on the end is useless in ceramic slurries. The shaft rotates opposite-to-normal direction. You have to 3D-print a large propellor (we can help you if needed), with that it will easily mix 2 gallons of thick, high-specific-gravity slurry (we replaced the 8" shaft with a 12" one).
Context: Propeller Mixer
Tuesday 12th March 2019
Drying mugs in front of a fan in 2 hours. No Cracks.
These are Plainsman Coffee Clay
. They, and the handles, were made on the wheel about half an hour ago, then stiffened enough in front of the fan to enable handle attachment. Coffee Clay
is plastic and will crack if pieces are not dried evenly. But if they are dried evenly, there is no problem. The handles were waxed after they were attached (leaving only a thin section on the inside where some water could escape). This slowed them down, otherwise they would have dried far ahead of the body. They went in the kiln and were ready for glazing the next morning.
Context: The Black Art of Drying Ceramics Without Cracks, Drying Crack
Friday 8th March 2019
Black and white cone 6 brushing glazes were easy to make
We started by adding 500 grams of the G2926B
Whiteware base clear to 250g of water and 100g of Laguna gum solution. It was possible to stir all the powder in without a mixer
. There were a few lumps left but they broke down overnight (yielding about 550 ml at 1.58 specific gravity
). For the black we added 30g more of Mason 6666 stain (6%) and for white 50g of zircopax (10%). This increased the specific gravity
to 1.63, higher than pretty well any commercial brushing glaze
(if needed, there is plenty of room to add water to thin it for better application properties). The black recipe costs about 1.37 cents/ml for us to make (compared to Amaco C-1 Obsidian @ 3.92 cents/ml to buy). But the situation gets even better: If we were to add enough water to bring the specific gravity down to the 1.4 of C-1 there would be far more than 550ml.
Context: G2926B - Cone 6 Whiteware/Porcelain Transparent Base Glaze, Brushing Glazes
Sunday 3rd March 2019