Fired bars of a bentonite used in porcelains! Is this possible?

Monday 25th August 2014

Perhaps you are shocked that a material this dark and dirty (the bars are fired from cone 1 to 7 oxidation, bottom to top), would be used in porcelains. Why? Bentonites are very difficult to process. This is just raw insight-live.com/material/106">bentonite (HPM-20), dry ground to -325 mesh (to guarantee no fired specks). That grinding does not reduce the soluble salts (that melt by cone 4) or the iron (which accounts for the dark-burning color). These undesirable properties must be tolerated (as whiteness loss) to get the plasticity supercharge 3-5% of this can impart. Why not use super-white bentonites or smectites instead? They can cost ten or even twenty times more!

Pages that reference this post in the Digitalfire Reference Library:

HPM-20 Volclay Bentonite, Bentonite, Soluble salts as a white powder on a commercial bentonite, Efflorescence

This post is one of thousands found in the Digitalfire Reference Database. Most are part of a timeline maintained by Tony Hansen. You can search that timeline on the home page of digitalfire.com.