|Monthly Tech-Tip |
We are reformulating the cone 10R stoneware (the top mug) to have the variegated surface of the lower one. The top one is more vitrified and thus has a more homogeneous grey color. While that makes it stronger it carries the danger of bloating with the materials we use and particle sizes we grind (and warping). We measure degree-of-vitrification using the SHAB test, that produces fired shrinkage and porosity data. The top mug has a porosity of 1.3% and the bottom one 2.5%. That higher porosity gives protection against bloating and the light/dark variegated aesthetic we also want. The nine test bars on the left each show their porosity/firing shrinkage and recipe (our materials have simple names like A2, A3, 3C, they include ball clays, silts, stonewares). We made these nine mixes trying to find a combination that yields the desired porosity but also does not have more than 7.5% drying shrinkage (to avoid drying cracks), is plastic enough for easy forming and does have too sandy of a texture. The second from the top is the best so far and has given clear direction for the next round of testing. These nine tests were fired at five temperatures producing 45 specimens to track and 180 measurements to make to get the final data (just for this SHAB test, others were done also). Our account at Insight-live.com makes it possible to track this plus 50 other projects on the go right now. And it makes it possible to make decisions based on data.
A cloud-hosted ceramics-targetted LIMS (lab info management system) where technicians manage, develop, adjust and study their recipes, materials and processes.
The term vitrified refers to the fired state of a piece of porcelain or stoneware. Vitrified ware has been fired high enough to impart a practical level of strength and durability for the intended purpose.
SHAB Shrinkage and absorption test procedure for plastic clay bodies and materials