|Monthly Tech-Tip |
These are cone 6 commercial glazes made by a popular US manufacturer. The body is a cone 6 casting porcelain made by another popular manufacturer. Zoom the photo, they are all crazing! Which company is at fault? Neither has the responsibility (or is able, especially with stonewares and porcelains) to match their product to that of every other company. The pattern we see here points-the-finger at the body. Mid-fire porcelains craze glazes much more if they lack sufficient silica (20% is minimum). It is difficult for manufacturers to achieve this since much more feldspar is needed to vitrify the body. And the potter does not know the recipe of the porcelain. What to do then? One option is to get a porcelain from another supplier, with assurances from them about glaze fit. Better yet, mix your own. Casters need a mixer anyway, so why not? We can help you with a recipe if you need it. Actually, mixing your own glaze also would get rid of those micro-bubbles and give a glassier surface.
The deflocculation process is the magic behind the ceramic casting process. It enables you to make a slurry of far lower water content and thus lower shrinkage.
Fluid Melt Glazes
Fluid melt glazes and over-melting, over fired, to the point that they run down off ware. This feature enables the development of super-floss and cyrstallization.
A method of forming ceramics where a deflocculated (low water content) slurry is poured into absorbent plaster molds, forming a layer against mold walls, then poured out.