The information in this glaze course has been written with idea of synchronising practical experiments in glaze making with the theoretical knowledge of glaze chemistry. This course was developed when I was teaching a glaze course in India, so I have kept out a lot of confusing detail and simplified the concepts where possible. During the lesson sessions additional information is given out if students require either more detail, or if a particular student’s problem requires more information. The analysis of materials and results is also done blackboard style and so no notes are available.
If you intend using this information in a course please credit your source – me!
If you are using this information for your own development then good on you, and good luck with your tests.
This practical course covers the basic ideas of experimentation and ties in with the thereoy pages. It does require access to a range of common glaze materials and equipment, including a kiln capable of reaching 1280 degrees.
Much of my early understanding about glaze chemistry arose through the use of a piece of software called HyperGlaze. This software analyses glazes and is immeasurably useful when learning about what materials do in a glaze and how the relationship between materials and oxides works out in a glaze. Of course much testing is still needed, but at least you have a tool that can quickly get to the heart of glaze chemistry. The tests listed have all been initially developed using HyperGlaze.
|Cone 08 - 1||Cone 1 - 6||Cone 6 - 11|
|Soda Frit or Feldspar||20|
If you are low firing and have no access to a borax frit then crushed clear glass will work as well.
The talc is added partly as a filler at low temperatures, partly as a flux at high temperatures and partly as it imparts a smooth creamy quality to the engobe in the wet form.
The zirconium silicate is an opacifier and help to whiten the slip.
To mix the borax in, first dissolve it in some hot water, then add to the engobe. It is used to make the engobe dry hard on the pot prior to firing.
Below is a list of colourants that can be added and the range of percentages used.
|Black||Black Iron Oxide||8%|
|Blue||Cobalt Oxide||2.5% - light < 7.5% - dark|
|Brown with specks||Manganese Dioxide||3% - light < 8.5% - dark|
|Brown||Red Iron Oxide||8%|
|Buff with specks||Ilmenite||6%|
|Grey with brown hue||Copper Oxide||3%|
|Forest Green||Chrome Oxide||2.5% - light < 7.5% - dark|
|Pink||Red Iron Oxide||2%|
|Tan||Rutile||3% - light < 9% - dark|