|Monthly Tech-Tip |
Fired to cone 6. These are not glazed. Polar Ice is very vitreous and very white, an ideal host for stains. However there is a caution: It has a high firing shrinkage. If a stain is refractory it can reduce that shrinkage considerably. On the other hand, some stains will flux it and drive the shrinkage even higher. That means if that if high and low shrinkage stained versions of Polar Ice are laminated the firing will create a tension-time-bomb that either exits the kiln cracked or cracks down the road. This work is courtesy of Robert Barritz.
Robert has done really valuable work in this research, what an amazing range of color! I am so grateful he shared this with the rest of us. Surfaces are unpolished and unglazed. All are fired to cone 6. Browns are missing, they can be made using iron oxide. For blacks, Mason 6600 is also effective. The blues require lower percentages than shown here, as low as 2% can be effective. Likewise with others, there is an optimal amount for each stain, beyond that, with increases in percentage the color intensity increase will drop significantly. There is another reason to keep stain percentages to a minimum: To reduce the impact on body maturity (and firing shrinkage). Blues, for example, can significantly heighten the degree of vitrification, even melting the porcelain. If you plan to marble different colors, keeping stain percentage as low as possible is even more important, unless you can do fired shrinkage compatibility testing, for example, the EBCT test. Need to develop your own white porcelain? See the link below.
|Materials||Mason 6308 Stain|
Ceramic stains are manufactured powders. They are used as an alternative to employing metal oxide powders and have many advantages.