How to Make Glazes for Clay
Pottery is an ancient craft, relying on extremely high temperatures to bake clay compounds into a hard, durable form. The heat of the kiln, which hardens the clay, can also be used to melt various substances onto the surface of the pottery vessel, making a hard, glossy colorful glaze. Glazes add to the beauty of a piece, and can also offer practical advantages such as water resistance. They can be compounded at home with a modest investment in equipment and materials.
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Things You'll Need
- Glaze materials, such as pumice stone, calcium carbonate and iron oxide
- Mortar and pestle, or other grinder
- Dust mask, commercial grade
- Stainless steel bowl
- High quality scale, accurate to one gram or less
- Paper towel
- 2 Stainless steel buckets
- Fine sieve, 50 or 80 mesh
- Wire whisk, or immersion-style "stick" blender
Instructions
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Organize your glaze materials near your workspace. If you haven't purchased them in powder form, use a mortar and pestle to grind the pieces as finely as possible. Wear a government-approved, commercial grade dust mask, to avoid breathing the dust. Wash the mortar and pestle carefully between ingredients.
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Place a stainless steel bowl on the scale and "tare" it, or adjust it so it reads zero. Measure out your first ingredient into the bowl, and then transfer it to a stainless steel bucket where it will be mixed. The bucket needs to be twice as large as your batch of glaze, so if you're mixing one quart of glaze use a 2-quart bucket. Repeat the process until you've weighed all the ingredients and transferred them to your mixing bucket. Wipe the bowl with a clean paper towel between ingredients.
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Add 7 ounces of water for each pound of dry ingredients, or as directed in your recipe, and mix it thoroughly with a wire whisk or stick blender. Place a fine mesh strainer over the second bucket, and pour the glaze from one to the other to eliminated lumps and large particles.
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Wash the first bucket and fine mesh strainer, and repeat the straining process twice more using a stiff paintbrush to work the glaze through the mesh. The glaze can then be stored in an airtight container until you are ready to use it.
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Tips & Warnings
Glazes can be made from a wide variety of ingredients found at craft stores, but you can also find suitable glaze materials in your home. Common and inexpensive products such as kitty litter, toothpaste and antacids can be used in glaze making.
Pottery and ceramics are fired at specific temperatures, expressed as a number of cones. When selecting a glaze recipe, make sure that its firing temperature coincides with the temperature of the piece of pottery. Otherwise it may have an imperfect finish, or fail to adhere properly to your work.
Recipes can be made thick for brushing on, thinner for spraying, or very thin for dipping. Ensure that you add the correct amount of water for the planned application method.
A remarkable range of colors and textures can be achieved with a few basic ingredients. Take the time to read a good book or online overview before beginning, in order to understand the process and chemistry involved. Bear in mind the true color of your glaze will not be evident until after it's fired, so many potters construct a palette by glazing and firing small fragments of pottery, and recording which recipe was used for each one.
A good dust mask is mandatory, since some glaze ingredients can be highly toxic if inhaled.
References
Resources
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