Specifications

Putting Down a Foundation . . .
Underglazes
14
Underglazes, originally, was a term used to refer to
ceramic colors used under-the-glaze, like a foundation. The
term has now become a general term and a specific material
meaning. Generally the term refers to a product put on
greenware that is covered with a clear glaze. This can be a
translucent or opaque type of material. The translucent types
are referred to as "One Strokes" and are usually covered with
a glaze as well.
The use and application of both opaque and translucent
underglazes are varied. They can be intermixed in each
separate category or intermixed between the two. An
oversimplification is: Opaque Underglazes are mostly clay
with pigment and One Strokes are mostly pigment with little
clay. The amount of clay determines the opacity of the
product and requires the product to be applied to greenware
so that the products shrink at the same rate in the firing.
Application of Opaque Underglazes
•Applied to greenware.
• Lightly dampen ware with water before painting; this
allows better adhesion to the ware and helps alleviate
pinholes.
• Shake the jar well before applying. It should be the
consistency of melted ice cream.
•Applied with a soft brush. Ox hair or Sable brushes are
best. Can be applied with other methods, see below.
•Use the largest brush for the area covered.
•Apply three even smooth coats at right angles to one
another.
•Do not thin for general application.
•Can be intermixed to get more colors.
•Can be tinted with One Strokes.
• Fired to shelf cone 04.
•Water soluble.
• Thin with Mayco Media or water.
•All are non-toxic
•Generally a clear glaze finish is applied after firing to
bring out the true color and vividness of the product.
Underglazes can be used directly from the jar, but
should be put out onto a tile. Make sure the consistency is
the proper thickness, like melted ice cream. Dip the
dampened, blotted brush into the color. Fully load the
brush without dragging the brush on the side of the tile.
Apply the color in a flowing motion, if it starts to drag,
reload the brush. The clay will absorb the moisture from
the color, so care has to be used in the application. As you
flow the color on, avoid any ridges and runs. Brush these
flaws out as you are applying the color. On an embossed
piece do not allow excess color to build up. Brush the
excess out of the crevices as you apply the underglaze.
Apply the first coat; when the dark wet look has left, apply
the second coat at a right angle to the first; the third is
applied at a right angle to the second coat. This will assure
smoother coverage.
Sponging Opaque Underglazes
A sponge is used to apply underglaze to greenware when
texturing a surface, when graduating colors, or when blending
two or more colors on the same piece. A sponge can be used
on an embossed piece. It works well on large surfaces to get
a more even coverage.
A natural sponge works best for applying the color. Make
sure the sponge is not worn out or has been exposed to hot
water. It should have a general spring to it. The color
thickness should be the same as for general brushing. A
slightly dampened sponge is used and the color should be put
out onto a tile for better application and absorption into the
sponge. Pat the color onto the surface in an up and down
motion, with quick motion to avoid smearing or overloading
of the area. Place one dab next to and slightly overlapping of
the previous one completing the piece in a systematic way.
The sponge should be reloaded often. Apply four to five
coats of color to make up the difference of not using a brush.
Other Application Methods
There are several ways of applying underglazes other than
the two previous methods.
Banding: The color is applied onto a surface using a
banding wheel. The color should be slightly thinner to carry it
from the brush to the ware. Naturally the piece is round and
bands or stripes of color are applied while the wheel is turning.
The ware is moistened so the color does not grab from the
brush and the color can be thinned slightly with Mayco Media
to lessen the color from grabbing the ware.
Spattering: The color is spattered onto the ware giving a
speckled look. Using a spatter brush or stiff brush, the color is
loaded into the brush, then the handle end of another brush is
drawn towards you over the bristles of the loaded brush. Make
sure you protect the work surface because the speckles can
travel great distances to other projects.
Stippling: Thin the color slightly and spread it onto a tile.
Load a stiff brush and wipe off the excess color. Test on a piece
of paper each time the brush is loaded. Hold the brush so that
only the tips of the bristles will touch the surface of the ware.
Pounce the brush up and down, gently tapping the color into
place. This technique is used for smaller and tighter areas when
needed. This is good for rims of plates or to fill in design areas.
Embossing: The color is thinned slightly to flow out of the
detailing brush so that several coats can be applied. This will
give a dimensional look to the design. Three coats will be
needed to build color depth.
Polishing Underglaze
While the application of an Opaque underglaze can be
applied to ware in many ways from brushing to sponging,
there is an interesting technique that is very old. One of the
most striking looks is by polishing the surface of the color to
produce a soft sheen. This technique is unobtainable by any
other method and is unique to opaque underglazes. While the
surface is somewhat sealed, it is not waterproof. It is only