Lily Krakowski on sat 21 dec 02
Someone asked about color, so here goes.
Starting from the premise that "our" glaze is transparent or semitransparent
(like skim milk) or white:
Color is obtained in several ways. (I am skipping that color results in
oxidation and reduction may/will differ)
1. The clay body underneath. A clay body that contains a lot of iron or
manganese will bleed through into the glaze. Diverse well-known effects
such as "oatmeal " and lavender can be obtained by using iron and maganese
respectively in the clay body. Adding granular manganese or iron filings
will produce speckles. I am against manganese containing clay bodies
totally, so I am NOT recommending them, just telling you they exist.
Petalite bodies often give quite lovely oranges...again; petalite contains
lithium...lithium is considered a subtance to be avoided. The above is not
a recomendation but a statement of fact.
2. A colored slip under the glaze. Or a white slip over a dark body that
then provides a white "tableloth" under the colored glaze
3. The clay in the glaze. Self-evident. Slip glazes derive their color
from the clay in the glaze, but it should be noted that interesting effects
can be had by adding a strongly colored clay such as Red Art to the glaze,
to replace the regular clay in it, and , as needed, some of the flux.
4. What we think of as colorants. These are available as oxides and
carbonates, the latter being weaker--i.e. you need more to achieve a
specific tone than you would with an oxide--and as commercially made stains.
These colorants may, in and of themselves, be refractory or fluxes.
Therefore if you receive a glaze recipes that says "Carol's Green" or
"Randy's Red" be advised that the glaze in all probability has been
finalize around the colorant. That means that without the colorant the
glaze--in these two cases, not all, not remotely all--might be too
refractory.
Glaze color as achieved with colorants will be affected substantially by the
fluxes. Magnesium tends to turn cobalt purple; zinc turns chrome brown but
benefits cobalt blues. YOU MUST know what is in the material you buy--i.e.
talc and dolomite both contain magnesium--before you throw colorant into a
glaze using them.
There are three excellent sources of information on glaze colorants. There
is of course The Potter's Palette, and there is The Ceramic Spectrum. But,
at no coat, we have the Mason color charts listed in suppliers'catalogs.
These list what is IN the stains--you can learn a lot--and what fluxes and
sundry materials should or should not be in the glaze.
Last. Opacifiers can and do affect color. Not much but enough. Again this
is a matter of testing. Boron tends to create opalescence that also affect
the final look.
There is no quick and easy way to achieve the color one wants. This truly
is an area calling for patience.
Lili Krakowski
P.O. Box #1
Constableville, N.Y.
(315) 942-5916/ 397-2389
Be of good courage....
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