Duncan Mayco instructions for Overglazes



In the language of ceramics, the term “overglaze” refers to the group of colors (golds and mother of pearl) that are applied to a previously glazed and fired surface. These overglaze materials are then fired to a temperature considerably lower than the original glaze firing.


Gold overglazes are opaque and have the brilliance of 22-karat yellow gold or white gold

MOP (Mother of Pearl) is a translucent overglaze with a lustrous iridescence.

Their appearance is determined by the base glaze the overglaze is applied over:

On a gloss glaze, the overglaze will be shiny. On a matte glaze, the overglaze will be dull. Overglazes are normally applied over a fired glaze but can also be applied to mid-range porcelain bisque or stoneware.


Overglazes contain solvents and should be used in a well-ventilated area. Those susceptible to odors (such as pregnant women) should be especially careful to work only in areas with an adequate ventilation system. During firing, odors are not dangerous but can be offensive. These odors quickly leave the area; however, it is not desirable to work in the kiln area during firing unless the kiln has a vented hood and an exhaust fan.

Dinnerware Safety

Overglazes can be used on surfaces that come into contact with food and drink. Care must be taken to avoid hard scrubbing when washing overglazed ware, because of the possibility of scraping off the thin layer of metal or luster. Treat your overglazed pieces as you would fine china. Although overglazed ware will take repeated washings in a dishwasher, the overglaze will eventually wear away.

When using Mayco Overglazes, work in a clean, dust-free area with good ventilation. Your hands must be free of all oils, hand lotion and moisture.


  1. Apply an overglaze compatible glaze to cone 04
  2. Fire to cone 06 -
  3. Do not stir or shake overglaze
  4. Place a small amount of overglaze on a glazed palette; apply one smooth coat.
  5. Try to attain an even tint:
    1. Premium Gold tint should be red in
    2. Bright Gold tint should be brown in
    3. White Gold tint should be green in
  6. Do not let overglazes pool in an area; brush them out smoothly.
  7. Clean brush in Essence and let


  1. Apply an overglaze compatible glaze to cone 04
  2. Fire to cone 06 -
  3. Do not stir or shake
  4. Place a small amount of overglaze on a glazed palette:
    1. For a swirled look, swirl on one coat, overlapping
    2. For a smooth look, brush on all strokes in the same direction.
  5. Correct application should produce a light blue
  6. Do not let overglazes pool in an area; brush them out smoothly.
  7. Clean brush in Essence and let dry.


  1. If overglazes are accidentally applied on the wrong area, dip a cotton swab in Essence and wipe off misplaced color.
  2. If any areas are missed, go back and touch up before the metallic or the luster overglazes dry.
  3. For solid coverage with Premium Gold or Bright Gold, use either a yellow glaze or a yellow underglaze for best results; for solid coverage with White Gold, use a gray glaze or a gray underglaze.


  1. Overglazes dry in about one hour but overglazed ware can be fired while still The kiln must be clean, well- ventilated (do not overload) and follow a normal firing schedule.
  2. Overglazed items should be stilted for firing:
    1. Fire golds to witness cone 019 - 018.
    2. Fire MOP to witness cone 020.
  3. Fire on fast for an electric kiln. For manual kilns, operate on “low” for 45 minutes with the peepholes removed and the kiln lid fully open. The lid is then lowered to about 6 inch, and the kiln is turned up to “medium” for 45 minutes or until all smoke and odors have disappeared. The kiln is then turned on “high” and the lid lowered to about 1 inch. When the kiln is turned off, the lid and peepholes are closed.

Note: When using golds and MOP on the same piece, it is best to apply the golds first, fire to witness cone 019-018, and then apply the MOP and refire to witness cone 020.

 Working with Essence

OA901 Essence is used to thin overglazes, or re-wet dried out overglazes on brushes or inside the bottle. Other cleaning agents may contain water or solvents, resulting in the separation of overglaze during subsequent applications. You can clean brush in Essence and let dry, but it is wasteful to throw away gold. So, when done lustering, wrap the brush in foil, when you need to use it a few drops of Essence will bring the luster back. 


Choose from Mayco’s premium quality brushes to produce the coverage or strokes you wish to

achieve. To prevent cross-contamination between Gold and White Gold, the color of the handle coordinates with the overglaze to be used. Brushes used to apply Mayco Overglazes should be cleaned with Essence and wiped on a paper towel. Brushes must be thoroughly dry before use.




If crazing has sharp lines and spider-web appearance, it is in the gold overglaze and was caused by too hot a firing. If crazing is long and in just a few lines, the gold overglaze was applied too heavily.

Future prevention: Make sure gold overglaze is fired to witness cone 019-018.

Dull, smoky or cloudy appearance

  •  Application too thick heavy
  • Overloading the Kiln
  • Incompatible Glaze

Use silver polish or vinegar to polish ware.  Allow 1” to 2” between pieces in a gold firing.
Fire metallic off at witness cone 06. Do not reapply golds.

 Ware cracks in overglaze firing

 Defective ware has become weaker with each firing.

  • Thermal Shock

Future prevention: Allow adequate ventilation around the ware in kiln.

Follow proper procedures to prevent thermal shock. Be careful not to place ware too close to peephole or side of kiln.

 Fish eyes (circular separations in metallic exposing underlying glaze)

Dust or lint on wet gold surface; grease, oil or moisture droplets on ware or in brush.

If ware has not been fired, try to touch up area. ( If even coverage is not obtained, remove metallic with Essence, let dry and reapply.)

 Purple tint

Too thin on application of the metallics.

Apply more gold overglaze and refire.

Metallic sheen rubs off easily

Too cool a firing.

Apply more gold overglaze and fire to witness cone 019/018.

 MOP (Mother of Pearl)

Powders off

Applied too heavily.

Rub off with soft cloth, reapply 1 light coat of MOP and refire to witness cone 020.

 Turns brown in one area

Fired too close to open kiln peephole.

Refire to witness cone 020, being sure to stilt piece and place it away from peephole.

 Frosted look

 Fired too hot.

Fire off at a witness cone 06. Reapply new coat of MOP. Fire no hotter than witness cone 020.

Purple or blue shadows or smudges

Contamination in the MOP.

Fire MOP to witness cone 06 to remove, then reapply and refire. (Make sure brushes are clean.)

If you need more help with Mayco Products.

Technical Support (614)675-2031 technical@maycocolors.com