|Monthly Tech-Tip |
Alternate Names: OH #5, OH#5, Old Hickory #5 Ball Clay
A popular secondary clay used in both clay and glazes. This ball clay is the base for a number of very popular premixed plastic porcelain and whiteware bodies in USA. It is fires to a light grey color with about 13% shrinkage at cone 10. Many potters claim that this is the whitest firing ball clay available in North America. In the powder form it looks much more like a light beige kaolin than a grey ball clay. This ball clay works very well as a glaze suspender and hardener in amounts around 15% (if too much more is used it gels the slurry).
The manufacturer calls it a unique grade that is virtually carbon free and contains a high amount of kaolinite (Al2O3) content. It has excellent fired brightness along with good plasticity. It can be employed at typical ball clay percentages depending on the type formula. Formulas that are more demanding for dry and fired strength values may benefit from some M23 ball clay. The plasticity and strength values of this grade could also be improved by an addition of some sodium bentonite in small percentages to serve as an auxiliary plasticizer.
Crude Color: White
Dry M.O.R. (psi 50% clay/50% flint, cast bars): 305
Wet Sieve Residue, +200 mesh (%): 0.22
Water of Plasticity (%): 33
Linear Dry Shrinkage (%): 6.5
Solubles Sulfates (ppm): 115
Filtration (ml): 26
Specific Surface Area (sq meters per gram): 18.9
CEC/MBI (meq/100 ml): 9.5
Firing Shrinkage (%)
Cone 04: 4.5
Cone 3: 6.6
Cone 11: 7.5
Cone 04: 15.8
Cone 3: 12.7
Cone 11: 5.0
Particle Size (% finer than):
50 microns: 99
Median Particle Diameter (micron): 0.46
I poured 4 teaspoons of two glazes onto a non-absorbent butcher’s board and let them sit for a minute, then inclined the board. The one on the right employs Gleason Ball clay, the left one has Old Hickory #5 ball clay. Neither has any slurry property modifier addition. The one on the right has settled and on incline the watery upper is running off. The other has gelled and the whole thing is running downward slowly. Below I have begun to sponge them off, the one on the right is sticky. The most amazing thing about this: This difference appears despite that there is only 7% ball clay in the recipe.
|Materials||Spinks HC#5 Clay|
|Materials||No. 1 Glaze Ball Clay|
Ball clays are abundant and very plastic and are used in all types of plastic forming bodies. They are not as white-burning or refractory as kaolins but lower in iron and fluxes than bentonites.