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What are overglazes?
Overglazes are a group of products applied over a fired glaze surface. Their firing range is 019-015. This group of products includes colored lusters, metallic, china paint, enamels and decals.
How do I prepare a piece for overglazes?
Successful overglaze decorating starts with the greenware. Greenware should
be cleaned and bisque fired to shelf cone 04. Bisque firing to shelf cone
04 should dissipate gases and organic materials which cause imperfections
in the overglaze or glaze at low firing temperatures.
Can I handle a piece that I plan to overglaze?
It is best not to handle a piece that you plan to overglaze. When removing
a piece from the kiln after glaze firing, use a coffee filter or lint
free paper towel. Store the cooled piece in a plastic bag until you are
ready to decorate.
Should I use a special glaze when preparing my piece?
Simply make sure the glaze you have chosen is overglaze compatible. Your
application must be heavy enough so that the surface is very smooth. Overglazes
take on the appearance and sheen of the glaze to which they are applied.
This means a matte glaze produces a matte sheen and gloss glaze produces
a gloss finish.
What methods are used to apply fired metallic?
The most popular method of application is brushing; however, metallic
and luster overglazes may also be applied by sponge, stamp or spray. Do
not spray apply without proper personal protective equipment.
What type of brush should I use?
A high quality camel hair brush works best for all-over decorating. Proper
application is best accomplished using the largest brush suitable for
the item or area being decorated. Mayco synthetic Taklon brushes are soft
and versatile, making them great to use for liner, detailing and design
work. However, they are too firm for large areas of metallic and luster
applications.
What is the proper technique for applying metallic and luster overglazes?
The brush should be well saturated for all over coverage. Remove the excess
color by dragging the brush across the edge of the jar. Apply and distribute
evenly with firm strokes placed next to the last one, working wet edge
to wet edge. Metallic and luster overglazes contain leveling agents that
will continue to level out the coating for a minute or two after applying.
Metallic and Luster Colors Application:
For large areas, apply an even, medium coating to obtain the proper color
and fired finish. For line work and detail design, place a drop or two
of the chosen metallic or colored luster on a clean glazed tile or piece
of glass. Allow air to thicken the color for a minute or two before using.
Due to slight evaporation, air thickened overglaze will hold the applied
shape. Load appropriate brush and apply a medium coating for desired effect.
This is also the recommended method when stamping or sponging overglazes.
Stamp Application:
Spread thickened overglaze evenly on tile or glass with a rubber roller.
Load a rubber stamp and transfer to object. Replenish overglaze on tile
or glass frequently for proper loading of stamp.
Mother of Pearl Application:
Apply very light coating to insure a beautiful, iridescent fired finish.
Unlike metallics and colored lusters, apply Mother of Pearl unevenly to
bring out the colors. This uneven coating is best accomplished by swirling
or stippling with a brush immediately after the basic application. Remember
to keep the coating light, as too much Mother of Pearl results in a dull
or powdery fired finish. Mother of Pearl is most commonly applied over
a gloss glaze, either clear or colored. You can also apply Mother of Pearl
over matte glazes for a beautiful, satin iridescence. For a truly beautiful
and unique effect try Mother of Pearl over a fired coat of Bright Gold
or White Gold.
Can Mother of Pearl and Gold be applied and fired at the same time?
Yes, metallics and Mother of Pearl may be applied and fired at the same
time successfully, if you remember two important points:
1. Use a separate brush for each product bring applied.
2. Gold and Mother of Pearl must not touch each other. If you prefer to
have separate firing for metallic and Mother of Pearl, fire the metallic
first and the Mother of Pearl second. Fired metallics are more tolerant
of multiple firings. Exception: When metallic detail is to be applied
over Mother of Pearl, then apply Mother Of Pearl first, and the Metallic
luster after the second firing.
What is Dispersing Agent? (Is this necessary?)
Dispersing Agent is a type of product used for cleaning and decorating
techniques. The solution contains no water and evaporates very quickly.
This makes it perfect for removing fingerprints and film from the glaze
surface before decorating it with a metallic or colored luster. Because
of its fast evaporation, Dispersing Agent may be used to clean brushes
when changing colors in a technique. Dispersing Agent is used to create
unique effects with lusters and metallics by breaking up and intermingling
bands or patches of color.
How do I clean my overglaze brushes?
We recommend you use Mayco OV-8 Essence, which has special solvents to
remove lusters and condition your brush. Divide a small amount of Brush
Cleaner into two portions and place in glass containers. Mark containers
with appropriate name and number (Cleaner #1 and #2.) Before cleaning,
squeeze brush with paper towel to remove remaining luster.
Bath #1: Dip brush in cleaner, do not swish. Squeeze into paper towel. Continue dipping and squeezing 5 or 6 times, then go to bath #2.
Bath #2: Swish brush then squeeze into paper towel. Repeat process until no color appears in the towel. To protect brushes from dust and lint, store in closed container.
Should overglazes dry before firing?
It is best to allow metallics and lusters to dry in an area free from
contamination by dust, dirt, lint or moisture before firing. Overglazes
usually dry within several hours. To make a dust and lint free area, drape
a plastic painter's drop cloth over the front and back of a cleaned metal
shelf. Glue magnets to the bottom edge of the drop cloth to hold the plastic
down.
How do I fire overglazes?
The typical firing range is shelf cone 018 or to 752 degree Celsius. Ventilation
is the most important element in firing overglazes, next being air circulation
and an even heating cycle. Follow these firing procedures to insure bright,
vivid colors:
1. Stilt all items for proper heating and circulation
2. Leave plenty of space between and above pieces so smoke and other contaminants
can escape freely.
3. Operate kiln on "low" for 45 minutes with lid fully open
and peep holes open.
4. Lower lid to 12 inches (use shelf post to prop) with peep holes out.
Turn kiln to medium for 45 minutes or until smoke and odor have disappeared.
5. Turn kiln to "high" with lid open 1 inch for the balance
of the firing.
6. As soon as kiln has shut off, the lid and peepholes are closed completely
and allowed to cool down. When using automatic kilns, venting is still
a key element.
Troubleshooting Guide
Problem: Overglaze appears to be crackled or have fine separated lines.
Cause: At cone 019-018 some glazes begin to soften and move. This causes
the overglaze to crackle.
Solution: Make sure you fire the glaze at the hottest cone recommended
on the glaze label.
Problem: Circles, white spots, or spots of glaze showing through overglaze.
Cause: Result of moisture present during the overglaze application.
Solution: Avoid all sources of moisture, which will contaminate the piece
while decorating.
Problem: Poor adherence of the overglaze.
Cause: Insufficient firing temperature, poor kiln ventilation, and contamination
of the decorated piece.
Solution: Avoid all sources of moisture, lint and dust. Properly vent
your kiln and follow instructions on firing. Always use a witness cone
and fire to the highest recommended temperature.
Problem: Areas of brown and purple on metallic overglazes.
Cause: Coating of the metallic is too light
Solution: Maintain an even, medium application.
Problem: Powdery appearance or blistering of Mother of Pearl.
Cause: The result of an excessively heavy application.
Solution: Use a light coating and apply unevenly by swirling or stippling
luster for best finished results.
Problem: A dull or cloudy finish.
Cause: Insufficient ventilation.
Solution: Properly vent your kiln and follow instructions on fir
