Pottery and Ceramics Glaze Recipes
Troubles with your Glaze Recipes?
Why Glaze Recipes Sometimes Don't Work
Ok, a potter sees a piece with a glaze they really like.
They get the recipe, mix up a batch and are disappointed with the results.
Their glaze looks nothing like the one they originally saw.
Now, if this has happened to you, you know how maddening it is.
I will try and help you understand glazes, so you can get the results you want more consistently.
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All About Pottery Glazes
Glaze is affected by many things such as:
Final temperature
Even if it is fired to the same Cone, the temperature may vary from one part of the kiln to another.Two people might interpret the bending of the Cones differently.
Rate of change in temperature, particularly cooling rate.
That is the main reason why glazes look different when fired on a whole piece than when fired in a test kiln, because the smaller test kilns usually cool faster.
Clay Body
Color as well as the materials in the clay body.Iron in a clay will often cause spotting through the glaze or will act as a flux causing glazes to melt earlier.
The thickness or thinness of the application of glaze or the method of application, whether it is sprayed, dipped or brushed.
Variations In Materials
Glaze materials are taken from the earth and their compositions are not pure.There is always some variation from batch to batch and sometimes this variation is enough to affect the glaze in a substantial way.
Atmosphere
The amount of oxygen present or not present.The presence of other glazes nearby.
Particle Size Differences
If a material is available in 200 mesh and 325 mesh, these will melt differently and give different effects.Mixing And Screening
How well the materials are mixed and to what mesh they are screened will affect the final result.Venting
Whether and how much a kiln is vented can affect the final firing.As you can see, there are many factors, so it is not surprising that it is hard to duplicate a glaze.
Commercial glazes have to be formulated to work over as wide of a range as possible or they would not sell very well.
These glazes are not always perfect and they will vary too.
But they are usually chosen for their more stable properties.
Some people think commercial glazes tend to be boring.
You are not likely to get a beautiful commercial multi-colored breaking glaze, because to achieve such a glaze requires a very specific range of conditions.
Breaking means that it changes colors or textures around the piece, like where there is variation in thickness or surface texture.
Commercial low fire glazes are the most stable.
Because of the way they have been formulated and the lower temperatures they are fired at, they usually are very consistent.They can still be affected by the above factors, but are less susceptible to minor changes. People who work with low fire glazes are usually those who are looking for consistent, repeatable colors, rather than unexpected, breaking colors.
The higher the temperature, the more interaction there is between the clay and the glaze. A clay body will play an increasingly important role as you go up in temperature.
At Cone 6 there is some interaction.
At Cone 10 there is a lot of interaction.
There are other problems with traveling glazes.
A glaze that is stable for one person might run or spit all over your shelves, causing damage.
It can also be toxic.
You don’t have to know any chemistry, other than to see that there are many chemical compounds in this single ingredient.
There is Calcium Oxide, Magnesium Oxide and Titanium Dioxide.
Each of these ingredients contributes something to a glaze.
One batch of Cornwall Stone may differ from the next in the proportions of the ingredients above.
This can obviously affect how your glaze will perform.
It is for this reason that professional potters often buy their raw materials in very large batches so they can make sure they have the same composition once they get their recipe working.
It is to expensive to buy large quantities for part time potters who only mix a small amount of glaze at a time.
Now, you know about the dangers of using glaze recipes, and I suppose some of you are wondering where the heck you can find such recipes.
Well, we have some recipes, Click on the links at the top of this page, for fun and interesting glaze recipes.
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