Raw Glazing And Once Firing Pottery, at 1050 °C

Once Firing Pottery / Raw-glazing clay

(Work in progress glazes)

All glazes here are fired in the Egg kiln and once-fired. Adding wet glaze to dry clay often causes stress and cracks in clay vessels. This page is about solving the problem and, at the same time, finding good glazes. All glazes are fired to their max in 3 hours.

Try using strontium as a high-fire flux

C04BG-001

20 – Gersley Borat
20 – Colemanite
10 – Feldspar soda
10 – Light Rutile
10 – Kaolin
10 – Bentonite
20 – Quarts
—
(I forgot the color i the receipt)
2 – Copper Carbonate
5 – Red iron oxid

Fired all too high, the glaze should be glossy, but when fired too high, it first seemed to drip off (on the pottery lower down the kiln), and then the flux boils, froths, or volatilizes boron oxides, leaving the glaze all to dry.

C04BG-002
Green Glossy

20 – Gersley Borat
10 – Colemanite
20 Sodium bicarbonate
10 – Kaolin
10 – Bentonite
30 – Quarts
—
2 Copper Carbonate

Difficult to apply evenly with a brush, don’t know if red ethanol makes it difficult or if water would react in the same way. When applied and dry, it’s really porous, and even the slightest touch makes the dry glaze crumble off.
This glaze was burned too high, and the flux boiled, froth, and volatilized boron oxides, dripping glaze and leaving the pottery with all too little glaze.

C04BG-003
The Darkest Hour

30 – Sodium bicarbonate
20 – Gerstley Borate
30 – Nepheline Syenite
10 – kaolin
10 – Quarts
—
20 – Iron oxide black

Nice and smooth to apply with water and a brush. Fired all too high, even if the glaze was applied evenly, the over-fired high temperature made the glaze roll of areas of the claybody.

C04BG-004
White-ish

30 – Borax Frits P2953.1
20 – Zink oxide
20 – Talc
10 – Magnesium Carbonate
10 – Kaolin
10 – Quarts

Nice and smooth to apply with water and a brush, fired all too high, all too dry, flaked off.

C04BG-005
Wood ash

30 – Gerstley Borate
20 – Sodium bicarbonate
20 – Wood Ash
10 – Kaolin
20 – Quarts
—
5 – Iron Oxide Red

Nice and smooth to apply with water and a brush. Bad picture, but this is a good glaze! I did not apply it too thick, and the green color is dripping from the other glazes.

C04BG-006
White-ish
20 – Gerstley Borate
10 – Sodium bicarbonate
20 – Feldspar Soda
5 – Magnesium Carbonate
5 – Chalk
5 – Talc
5 – Ilmenite
10 – Rutil
10 – Kaolin
10 – Quarts
—
5 – Blue stains

C04BG-007
White
30 – Alkali Frit P2962.1
20 – Feldspar Soda
20 – Magnesium Carbonate
10 – Chalk
10 – Kaolin
10 – Quarts

C04BG-008
Best white
60 – Ferro Frit 3134
10 – Chalk
10 – Kaolin
30 – Quarts

C04BG-009
Best white
50 Colemanite
30 Feldspar Soda
10 – Kaolin
10 – Quarts
—
10 – Burnt Ocer

C04BG-010
White dry spotty

Dry, interesting, but needs to be more glossy
20 – Gerstley borate
20 – Sodium bicarbonat
10 – Light Rutile
10 – Tin oxide
10 – Kaolin
30 – Quarts
—
5 – Red stains

Over-fired with maybe 150 degrees, try again

C04BG-011 – White base

20 – Borax
20 – Gerstley borate
20 – Sodium bicarbonat
20 – Kaolin
20 – Quarts

As a base glaze, it has some problems with pinholes and cracking, but it’s a good start, and I like the hard surface. Over-fired with maybe 150 degrees.

C04BG-012 – White dry

10 – Gerstley borate
20 – High alkali frit P2962.1
20 – Magnesium Carbonate
10 – Chalk
10 – Kaolin
30 – Quarts