Olive green
Iron oxide 5
Cobalt oxide .5
Dark brown
Iron oxide 3
Nickel oxide 2
Manganese oxide 5
Light gray-blue
Tin oxide 5
Cobalt oxide .5
Copper oxide 1.7
Blue-green
Cobalt oxide 1
Copper oxide 7
Yellow ochre 4
Dark gray-blue
Nickel oxide 5
Yellow ochre 3
Cobalt oxide 2
Copper oxide 1
_Applying the Glaze._--Before applying the glaze to the piece of
pottery or bisque, the latter should be soaked in clear water for
about five minutes or until the air is expelled from the pores. When
this has been accomplished it should be removed from the water and all
moisture should be wiped from its surface. The piece is then ready to
be dipped into the glaze, or to have the glaze poured over it, if the
size and shape of the piece make it more convenient to apply the glaze
in this way. It is usually best to glaze the inside first, shaking out
all the superfluous glaze before applying the glaze to the outside.
During this process the piece must be held firmly but by as few points
of contact as possible. These points of contact will generally need to
be touched up before it is ready for firing.
It is sometimes necessary to glaze large pieces with a brush, putting
on several coats in order to cover the surface with an even thickness.
The matt glaze requires a greater thickness than the bright glaze
in order to develop its characteristic velvety texture. The greater
thickness may be easily secured, because it flows more slowly than
the thinner bright glaze and is less likely to drip from the sides of
the piece to which it is being applied; but, on the other hand, it
is at a disadvantage in that it does not, in flowing slowly, correct
inequalities of thickness so readily as the more mobile bright glaze
does. A certain thickness, however, is essential; and if, after firing,
it is found that the glaze was put on too thin, a second coat may be
applied and the article again fired.
_Firing the Glaze._--Before the glazed piece is fired the glaze should
be dried and what runs down and collects about the bottom or foot
should be scraped off. It should then be set in the kiln on a kind of
pointed tripod of hard burned clay, called the "stilt," which prevents
the glaze from sticking to the floor or shelves of the kiln. All glazed
ware should be placed in the kiln with at least 1/2 an inch of space
between the pieces to prevent them from sticking together during the
fusing state of the glaze, when it is apt to bubble or "boil."
The firing of glaze is a process very similar to that employed in the
production of bisque, already described. Greater care, however, must
be taken in controlling the increase in temperature so that it shall
be even and steady--free from all sudden flashes of heat. The cooling
also should be very gradual and, as in bisque firing, the kiln should
be allowed to get cool before it is opened. With this second firing the
pottery is finished unless it should happen that a second coat of glaze
is found to be necessary. If only a few spots need attention, this
second coat is best applied with a brush.