1. You will need Glaze Notes page and something to write with.
By Marni Oberpriller
Please DO NOT get your current
clay project out yet.
GLAZE NOTES

2. GLAZE VOCABULARY: What is glaze? What ingredients make up a glaze?
How is a glaze
different from an
Under-glaze?
A layer of glass that makes your vessel shiny, waterproof and food safe.
Silica: tiny particles of glass
Alumina: “glaze inhibitor” that keeps the glaze from running off the clay
Flux: brings down the melting point of silica
Pigment: color
These ingredients appear in various proportions.
The amount of Silica, Alumina and Flux determines the amount of color and opacity.
An under-glaze contains less flux.
This keeps the silica particles from
melting completely.

3. KILNS & FIRING: Low-fire High-fire Two Skutt Electric kilns,
Named “Thing 1” & “Thing 2”
Typically fired to 1800* F or Cone 06 oxidation.
Firing time: 12 hours to reach desired temperature, plus 12 hours to cool, total 24 hours.
One Geil Gas kiln
Named “Cat in the Hat” (look closely, the big kiln has a hat!)
Typically fired to 2400* F or Cone 10 reduction.
Firing time: hours to reach desired temperature, plus 72 hours to cool, total 96 hours.

4. KILNS & FIRING: What type of Firing is done at JHS?
High-Fire: The silica melts within the glaze at 2382 degrees/Cone 10.
Oxidation: The amount of oxygen remains the same inside the kiln as it does outside the kiln.
Reduction: Where the amount of oxygen is reduced in the atmosphere of the kiln.
The reduction method can be unpredictable depending on the amount of oxygen in the kiln. As the oxygen is reduced and amount of gas is increased, the fire pulls oxygen from wherever it can, including the clay!

5. GLAZING MATERIALS: What type of high- fire glazes do we use at JHS?
Glaze particles work best when suspended (floating in the barrel). An electric mixer can help to suspend the particles
Glaze: color and the shine all in one glaze. Samples of these glazes are found on the wall (large).
Under-glaze: color is consistent, but no shine, not food safe (jars).
Shine comes from clear over-glaze applied later.
Samples of these glazes can be found on the wall (small)
Stain: pure pigment. Painted on, then wiped off. Makes texture stand out. Ask about using a stain.

6. TERMS USED TO DESCRIBE GLAZES:
Transparent:
Opaque:
Glossy:
Satin:
Matte:
Semi-_____:
Food-safe:
can see through glaze
solid and not see-through glaze
shiny
partial shine
no shine at all (not food safe)
Partially, or a little bit _____
Safe to eat or drink out of

7. STEPS IN GLAZING:
Form must be bisque-fired first! Clay body must be pink.
Wash any dust off the clay surface.
Ensure under/glaze is properly mixed and particles are suspended in the barrel.
Shake jar with lid on tight
Mix by hand using wand or whisk (clean tools at sink or bucket)
Use electric mixer (clean using water bucket).
Brush/Dip/Pour glaze using clean brush or cup.
Use a brush to apply 3 solid coats of under-glaze on all surfaces except the bottom.
Apply glaze to the inside surface of your form first.
Remove any unwanted glaze. IMPORTANT: ALL GLAZE is to be REMOVED FROM THE BOTTOM OF YOUR FORM BEFORE FIRING!
Wipe wet glaze with a sponge or carpet mat (clean tools after use)
Scrape wet or dry glaze using the glaze scrapping tools.
Put glaze-ware on the cart marked “Glaze-ware/#3” for firing.
Pour back extra glaze into jar; wash all brushes/cups and work surfaces.

8. GLAZING TECHNIQUES: Brush-on Glaze may be applied by using a brush.
Do not use under-glaze over an entire form. Use under-glaze as accent colors
Glaze goes on form only where applied with the brush – perfect for fine details.
Clean up:
Wash brush and return brush to cart with bristles UP
Wipe bottom of clay form with a sponge
Wipe work area with sponge
Wipe glaze jar with sponge.

9. GLAZING TECHNIQUES: Parts of a Brush
Under/glaze may be applied by using a brush.
Glaze goes on form only where applied with the brush – perfect for fine details.
Avoid dipping brush into container. Pour a small amount of under/glaze into a bowl (you can always add more later if needed).
Return any unused under/glaze to original container, and rinse bowl.
Avoid getting glaze on the FERRULE of brush.
Clean up:
Wash brush and return brush to cart with bristles UP
Wipe bottom of clay form with a sponge
Wipe work area with sponge
Wipe glaze jar with sponge.
Parts of a Brush

10. GLAZING TECHNIQUES: Dip
Choose a glaze or combination of glazes to be dipped (review test tiles on the class wall).
Always glaze the inside of the form first.
Glaze is applied by holding onto the form and dipping the entire form or partial form into the glaze barrel.
Glaze will cover the entire form and must be removed from the bottom of the form before firing.
You can overlap applications of different glazes to create new colors – check test tiles for effects!
Clean up:
Replace lid on bucket
Wipe bottom of clay form with a sponge
Wipe work area/surface/floor with sponge
Wipe glaze jar with sponge.
Wipe glaze-mixing tools with a sponge or swirl in water bucket.

11. GLAZING TECHNIQUES: To pour a glaze:
Choose a glaze or combination of glazes to be poured (test tiles).
Always glaze the inside of the form first.
Using a clean cup, fill the cup with glaze by dipping it into the barrel.
Glaze is applied by holding the form and pouring the glaze over the entire-form or partial- form while over the glaze barrel. Allowing the glaze to go back into the glaze barrel.
Glaze may cover the entire form but must be removed from the bottom of the form before firing.
You can overlap applications of different glazes to create new colors – check test tiles for effects!
Clean up:
Replace lid on bucket
Wipe bottom of clay form with a sponge
Wipe work area/surface/floor with sponge
Wipe glaze jar with sponge.
Wipe glaze-mixing tools with a sponge or swirl in water bucket.

12. GLAZING TECHNIQUES:
To spray (we don’t have the tools for spray application at JHS)
Use a sprayer tool and spray booth (requires ventilation) and spray nozzle to apply the glaze to the surface of the form.

13. HELPFUL HINTS… 3 is a magic number for brushing under-glaze layers.
High-fire glazes can be brushed, dipped or poured.
Apply to inside first
Less is more
Wipe the bottom clean of any glaze. Place vessel on glaze-ware cart