Radagast97 replied to Kristine's topic in Clay and Glaze ChemistryI agree with the previous posters, most cone 5 clay's should work, but also remember that different parts of your kiln may fire differently. It's not unusual to get a cone 5 at the one part of the kiln and 6 1/2 in a different part. Be sure to use a few cone packs to ensure you know what all the parts of your kiln are firing to.
No, it won't. Calcium has relatively low vapor pressure. Also remember the amounts in a glaze a fairly low. If they were higher it would affect the clay and glaze. Once the glaze starts to melt, it really doesn't care what compound the calcium came from - it just sees it as calcium oxide. If you want a substitute for calcium chloride with an extremely low vapor pressure, use a little epsom salts (magnesium sulfate). It does the same thing, flocculation-wise, with zero vaporization potential. Sodium, lithium, and potassium salts have a much higher vapor pressure - which means if a pot is glazed with a high potassium/sodium/lithium glaze and is close to an unglazed pot, you'll get a hint of a vapor glaze on the portion closest. I take advantage of this property by adding a small amount of potassium nitrate to my wax-water emulsion resist. It turns the unglazed feet of my pots from an uninteresting peach color to a light toasty color. YMMV Keep in mind calcium chloride forms very low melting point hydrates and is excellent at sucking water out of the air. Keep it in an open containing on a warm, humid day and you'll return to a big puddle. That said, soluble calcium or magnesium compounds (and on +2 charged ions) with flocculate a glaze, not deflocculate. To deflocculate you use something like sodium silicate. However, most people don't want to deflocculate their glazes. Casting slips are deflocculated, but I've never seen anyone deflocculate a glaze. A deflocculated glaze will settle into a thin, hard, concrete like layer that's hard to mix back up. See: http://www.claytimes...eadjusting.html Rad