Apart from its obvious use in the decoration process of ceramic glazes, this is also used as a binder in ceramic bodies.
Related Information
Meet two glazes at the rim using wax emulsion. Why? How?
Reactive glazes (melt-mobile, crystallizing or heavily pigmented) are the least suitable for food surfaces because they have the potential to leach metals. Liner glazing ware is an excellent way to deal with this problem. Not only does this approach improve functionality but it can be aesthetically pleasing and practical in production.
This liner is GA6-B, a pottery glaze recipe we promote with confidence. Not only is it less likely to be leaching metals but also less likely to craze - this assures water tightness on non-vitreous bodies and eliminates any potential for bacteria growth in the cracks (especially if the body has porosity). Unfortunately, glazes that leach are also likely to stain and cutlery mark - these add more reasons why they are most often unsuitable for food surfaces.
The straightness of the dividing line is affected by both the application technique and the degree to which the two glazes bleed into each other and run. Read and watch our liner glazing step-by-step and liner glazing video for details on how to do this - it is practical for any potter or hobbyist (or even in production). And tap/click the picture above for other examples of this.
Wax resist inducing surface pinholes on a low fire transparent over an underglaze
Bubbles are appearing on the two sides over the blue underglaze (vertical wax brushstrokes were applied, not for functional reasons but just to demonstrate this issue). No wax was used over the transparent at the rounded corner or on the vertical centre of the blue area. This transparent, Spectrum 700, is normally ultra-clear and ultra-glossy, but over these Amaco Velvetunderglazes that transparency is fragile and the wax is enough to produce the micro pinholes. This is the Zero4 body so it has minimal LOI, suggesting the main issue is with the wax.
Worst case scenario for handle joins and successful drying
These M390 mugs had progressed to stiff leather hard (after handles were applied, using just slip, and bases trimmed). A white engobe was then applied to the inside. It significantly softened the bodies of the mugs (to re-dry them to the point of being able to turn them over takes 4-6 more hours). This process sets up a big moisture differential between mug and handle. "Even drying" is the key to success, so slowing down the handles is obviously needed. How? I apply wax emulsion (actually I like Reed Wax), leaving just the inside handle-curves bare. That slows down drying enough to keep them even with the body of the mug. This method works so well that these do not even need covering during drying (even in our desert climate). Even drying is the goal - fast and even drying is much better than slow and uneven.
Drying mugs in front of a fan in 2 hours. No Cracks.
These are Plainsman Coffee clay. They, and the handles, were made on the wheel about half an hour ago, then stiffened enough in front of the fan to enable handle attachment. Coffee clay is plastic and will crack if pieces are not dried evenly. But if they are dried evenly, there is no problem. The handles were waxed after they were attached (leaving only a thin section on the inside where some water could escape). This slowed them down, otherwise they would have dried far ahead of the body. They went in the kiln and were ready for glazing the next morning.
Wax emulsion arrived lumpy and thick
This is CrystalCer A from PMC Crystal, a manufacturer of waxes, wax emulsions, oils and soaps. In ceramics it is mainly used as a resist during the application of glazes. Using a propeller mixer we were able to thin it and remove the lumps.
Links
Articles
Binders for Ceramic Bodies An overview of the major types of organic and inorganic binders used in various different ceramic industries.
Typecodes
Additives for Ceramic Bodies Materials that are added to bodies to impart physical working properties and usually burn away during firing. Binders enable bodies with very low or zero clay content to have plasticity and dry hardness, they can give powders flow properties during pressing and impart rheological properties to clay slurries. Among potters however, it is common for bodies to have zero additives.
