Shula on sat 2 aug 08
It's Saturday night and my electric kiln is click, click, clicking away. My second bisque firing is underway. So, now it's about time that I start glaze testing. I've created two kinds of test "tiles." The one for the crystalline glazes is thrown and a variation of one I saw in a crystalline glaze book. It is tubular in shape (but closed at the top) with a lip at the bottom to catch the glaze. For non-crystalline glazes, I rolled a slab about 1/2 inch thick and cut 3 inch squares. I then attached two to create an upside down T formation - to catch any runs. I also used a shell to add ridges to one side of the vertical so that I can see what the glaze looks like when it breaks.
So far, so good.
Now, the question I have is how much glaze to make up when I am testing recipes. In the ideal glaze testing world which I currently inhabit, I would like to test the glazes using different firing schedules and cooling schedules. Therefore, I want to have enough glaze to cover several of my glaze "tiles."
My specific questions:
1. How many grams of glaze do you usually weigh out when testing a glaze?
2, How much (liquid) glaze does this translate to? (liter, pint, quart, whatever)
3. How many pieces and what kind of pieces do you usually test with this amount of glaze?
Thanks
Shula
Desert Hot Springs, California USA
When the ambient temp was 99.9 and humidity was 16% when I started the firing at 7:40 pm. The middle thermocouple in the kiln read 112 degrees at that time.
Des & Jan Howard on wed 6 aug 08
Shula
1. 100 grams.
Our larger digital scales go to 5000 gms in 1 gm increments. The
smaller scales go up to 100 gms in 10 mgm increments. All glazes
are calculated & noted as percentages. To the knockers of dig scales &
calibration, we have standard metal weights to check & recalibrate if
necessary, but never needed.
2. Depending on the broad glaze type we add 120 ml water (iron glazes),
110 ml (flambes, copper reds), 100 ml (Juns, celadons). The 240cc
plastic cups hold enough glaze & water to dip our standard test strip, a
75 mm length of scrap extruded mug handle. These pop into a lump of very
sandy plastic clay.
3. Glaze testing is usually done en passant, so, only one or two get
into a kiln. The glazes are dipped on our white porcelaneous & grey
stoneware bodies & placed in average spots in the kiln setting.
Des
Shula wrote:
> 1. How many grams of glaze do you usually weigh out when testing a glaze?
> 2, How much (liquid) glaze does this translate to? (liter, pint, quart, whatever)
> 3. How many pieces and what kind of pieces do you usually test with this amount of glaze?
--
Des & Jan Howard
Lue Pottery
Lue NSW
Australia
2850
02 6373 6419
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