search  current discussion  categories  teaching 

lesson seven part two

updated thu 10 aug 00


hal mc whinnie on wed 9 aug 00


Ash and salt glazes

"Ash glazes have a unique quality of their own. The color obtained range
from different shades of tan to brown and mustard to yellowish greens.
Some of the fluxes contained in the ash are potash, lime and magnesia; also
a high proportion of silica which in combination with the fluxes readily
forms a glaze. It also has small amounts of iron, which add color.

The proportion of ingredients vary from ash to ash, and can give several
ranges of textures and color in stoneware glazes which is otherwise
difficult to obtain. It is best to collect a good supply of ash before you
can use the same kind of ash in your glaze as in your test.
Because of the soluble potash in ash it is caustic and care must be taken
when applying the glaze in order to protect your hands. I have found it
better to wash the ash twice before using to eliminate some of the soluble
ingredients and to prevent the a
] Glaze from running down the sides of the piece, also its not so harmful to
your hands.

A simple glaze can be made from 50%ash and 50% of some kinds of earthenware
clay. [Part of the clay should be calcimined in order to adhere well to the
bisque ware.] I have used mangrove ash and iron clay in this proportion and
have found it quite successful. The color obtained was a greenish yellow
with a brown tinge. "[Vera Baney, a ceramic artist from Baltimore Maryland
and formerly of Trinidad in west Indies, written as a student paper many
years ago.]

Test a
50 ash
50 red clay

50 ash
50 white clay

test c
25 ball clay
25 barium
50 ash

Test d
50 ball clay
50 ash

Test e
50 ash
35 redart
15 barium carb


Cone 9-10

1] Albany clay 85
Cornwall stone 15

2] Rhodes black

Albany clay 65
Neph syn 35

3] Ann's blue

Custer spar 89
Whiting 10
Rutile 3%
Iron oxide 2%

4] Shaner yellow-red

Zircopax 23
Custer spar 49
Whiting 20
Talc 4
Bone ash 4
Iron oxide 4

5] Shanner red

Epk 23
Custer spar 49
Whiting 20
Talc 4
Bone ash 10
Iron oxide 4

6] Shaner mamo Matt

Epk 21
Custer spar 49
Whiting 4
Dolomite 19
Tin oxide 8