What is Glaze?

• A coating is applied over the surface of the bisque fired piece that when fired melts and forms a glass-like coating.

• Glaze: Made up of Glass Formers and Fluxes+ colorants and opacifiers.

• Glass formers: Silica and Clay.

• Fluxes: Melters, can reduce the melting temperature.

• Colorants: Cobalt=Blue, Iron=Brown or Red in Reduction, Copper-Pale green, Chrome-bright green or pink with Tin

• Opacifiers: Make the glaze more opaque or less see-through, or white. Tin and Zircopax are opacifiers.

• Types of Glaze Texture: Matte, Shiny, Special Effect, Breaking

Why Glaze?

• Decoration: It looks beautiful and adds color and surface texture.

• Functionality: When you glaze the surface, any pores are sealed so the piece will hold water and will be easy to clean.

• Strength: When you glaze fire a piece it becomes vitrified or glass-like which makes a pot more durable.

Glaze Application

• The neater you are in applying your glaze, the nicer the result will be.

• Some glaze ingredients are toxic and care should be used when working with glazes.

• Wash your hands thoroughly after. Wear gloves or avoid getting glaze on your hands. No eating or drinking while working with glaze.

• The glaze should be applied to about a dime thickness.

• Glaze applied too thickly could result in running, or crawling.

• Glazes can be overlapped as long as they do not get too thick.

• The previous glaze should be completely dry before applying the next layers of glaze.

• Glaze "A" overglaze "B" will not necessarily look the same as glaze"B" overglaze "A" or the same as Glaze "A" & "B" mixed together.

• Testing is super important.

• Common methods of Applying glaze: Dipping, Pouring, Brushing, Spraying

• There can be no glaze on the bottom of a piece or it will stick to the kiln shelf.

• The excess glaze should be wiped away with a damp sponge.

• Because any glaze can run, the glaze should be wiped up to 1/4 inch from the bottom of the piece.

• If the piece is cracking or glaze is falling off or glaze is not drying, all glaze should be washed off. Dry the piece thoroughly, then reglaze another time.

Glaze Firing

• We glaze fire to cone 10, which is considered high-fire. Some studios glaze fire to cone 6, which is considered mid-fire.

• Glaze when it is melted will stick to anything it touched in the kiln.

• Bisque firing is important so there is less chance of pieces exploding and sticking to other pieces.

• Types of Glaze Firing- Oxidation-Electric Kiln, Reduction-Gas Kiln, Atmospheric- Raku, Soda, Salt, Wood

• The glaze firing is faster and goes to a higher temp. Usually to Cone 10-over 2300 degrees.

Glaze Flaws

• Crazing: A web of tiny cracks that spreads through the glaze on your piece. It is often seen in antique pottery. Some people like the look, but it does weaken the piece.

• Crawling: Blank spaces on your piece where the glaze has moved away. Usually happens on pieces in which the glaze is flaking off prior to firing.

• Pin-holing: Little holes or craters in your glaze. Could be caused by glazing a wet piece.

• Running: When the glaze runs off the piece, causing an ugly mess on the kiln shelf, and a sharp jagged surface on the bottom of your piece. Careful! Remember, the glaze is glass, so don't run your fingers over any surface that ran off your pot. Usually caused by the glaze being too thick.