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
Possible to grind your own ceramic grade rutile?
Yes, the granular and powdered grades are the same material. But grinding it is very difficult. Commercial ceramic grade powder is minus 325 mesh, the companies doing this obviously have very good grinding equipment. They also have patience because even in this efficient porcelain ball mill, 90 minutes was only enough to get 50% to minus 325 mesh! The color of the powder is a good indication of its quality, the finer the grind the lighter will be the tan coloration.
Context: Ceramic Rutile, Granular Rutile, Making your own ceramic rutile
Saturday 2nd March 2019
Stunning black silky matte glaze at cone 6
This contains 6% Mason 6600 black stain (Mason 6666 gives dark brown, don't use it). The base recipe, G2934
, is an excellent balanced-chemistry
host for a wide range of stains to produce equally stunning reds, yellows, oranges, etc. The fritted
version of the recipe, G2934Y
, provides an even better host. This glaze is affected by the clay it is on. The body on the right is highly vitreous
, this has produced a finer texture that glistens in the light. The body on the left is a whiteware having 1% porosity
(Plainsman M370). Firing schedule is also a factor, slower cooling will dull the color more. We use the PLC6DS
Context: G2934Y - Cone 6 Magnesia Matte Low LOI Version, G2934 - Matte Glaze Base for Cone 6
Wednesday 27th February 2019
Mix a whole bag of G2926B whiteware clear glaze
When you mix it right it will be thixotropic
, that is, it will gel slightly and hold itself on the ware after dipping. This state can only be achieved if there is enough water for the epsom salts to do their magic. The watery nature of the slurry is nice for measuring specific gravity
using a hydrometer (normally they don't float freely enough if the slurry is creamy). We normally recommend a specific gravity
of 1.44 for this glaze, but in this case it seemed watery enough at 1.46. On use it will become clear if 1.46 is OK. How? It will go on the ware too thick. If that happens just add water to 1.44 and add more epson salts to gel it back up.
Context: G2926B - Cone 6 Whiteware/Porcelain Transparent Base Glaze
Friday 22nd February 2019