Ceramic overglaze, Pyrometric cones, Loading and firing overglaze – Elmer's Glass Kiln User Manual

Page 13: Firing enamel

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agent to keep the grains of enamel in place. Allow the enamel

to dry completely before firing.

Firing Enamel

1 Heat the kiln to 1450°F/787°C for most enameling.

Use a Single Segment. (Please see your digital con-

troller instruction manual.)

Rate

Temp.

Segment

°F/°C

°F/°C

Hold

1

1799/999

1450/787

01.00

Note: Hold time should be the length of time you

will be inserting enameling into the kiln. In the

above example, hold time is for a one hour.

2 Lay the copper shape on an enameling rack. If the

part that touches the rack is enameled, place a stilt

under the copper. Some bowls or other shapes have

enameled sides that might run during firing. These

should be fired with a stilt even if the piece has a plain

bottom. Use an enameling fork or, if the rack is small,

a 6” putty knife, to place the rack into the kiln on top

of ½” ceramic posts.

Note: Firing the piece at enameling temperature

should take about three minutes and requires undi-

vided attention!

3 Look at your piece every 15 seconds by cracking open

the door. Remove the rack when the copper piece ap-

pears a rosy red and the enamel is smooth. Place the

rack on a steel pad or large ceramic kiln shelf and let it

cool completely.

4 After counter enameling, you will need to clean the

fire scale off the front of the piece. A 3M Scotch

Brite® pad works well for this. Then clean it with

Thompson Sparex No. 2.

Ceramic Overglaze

Pyrometric Cones

Pyrometric cones are small pyramids of clay and mineral

oxide that soften and bend

when exposed to heat. They

indicate when ceramic ware

has fired to maturity.

Pyrometric cones come

in 1 1/8" and 2 ½" lengths.

Use the 2½” cones. Cones

mounted on the kiln shelf

must be slanted 8° from ver-

tical. They will not bend ac-

curately if they are slanted

to the wrong angle.

Self-supporting large

cones have the correct slant

built into the base. Stan-

dard cones must be

mounted in a clay or wire

plaque.

The chart on page 14

shows the temperatures of

pyrometric cones. Program

your controller to the cone

recommended for the ce-

ramic ware that you are

firing.

For small ceramic

pieces, such as figurines,

program a rate of

400°F/222°C. Fire to the

temperature shown in the

108°F column of the Tem-

perature Equivalents chart

for the cone number you

are firing.

Before deciding on the

firing speed of important pieces, test fire sample clay pieces.

Note: Do not fire beyond your kiln’s maximum

temperature. Firing hotter will void your warranty.

Kilns with glass view port: do not fire hotter than

1700°F/926°C.

Loading and Firing

Overglaze

Overglaze is decoration applied over fired glaze or pol-

ished porcelain bisque. Overglazes include china paints,

gold, and luster, which fire from cone 022 to 014.

Load overglazed ware the same way you would load ce-

ramic glaze. Use stilts and make sure ware is not touching

other ware. Ware must be completely dry before firing.

13

A self-supporting cone fired to matu-

rity. Do not be concerned if the tip is

slightly higher or lower than shown.

A “puddled” over-fired cone.

Under-fired cone.

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