Another firing possibility
Aug 5, 2015 7:34:50 GMT -6
Post by tileman2 on Aug 5, 2015 7:34:50 GMT -6
Greg:
Thank you for the insights: gives me a general direction to head in. Have made notes about reduction for years: but notes and doing it are two different realities. If I kick on the exhausts; it will completely turn over the air in the detached garage roughly every 60 seconds.
Some thoughts and experiences with copper and "boil off." I have tested nearly a dozen different zincs; most sent as free samples from various companies to be tested in crystalline glaze. "Yellow" zinc as we commonly call it will not boil off because it is made by the American process. This just means it is refined ore that has been roasted, washed, and put through a rotary kiln to burn off impurities: then finely ground. The only time there is a reaction with copper that gives the appearance of boiling off is when high amounts of lithium is used: so lower cone firings can be obtained. In reading numerous articles: in reality zinc does not reach its assigned boiling temp: it vaporizes before hand. When that occurs: it has an appearance of boiling: and high amounts of lithium contribute to that problem.
The real problem I have found is with french process zinc; which is made by capturing the vapors from zinc ore or zinc ingots that are intentionally high fired to cause vaporization. The primarily reason all french process zincs are extremely high in purity. Cerox 506 is in fact a french process zinc: but processed from an ore very low in sulphur (yellow color). Then it is highly calcined: the processing method makes it highly resistant to boiling off (vaporization.) Anyone using Cerox506 will probably never experience this problem unless they dump boat loads of lithium in it.
Then there are french process zincs that are cone 6 primarily: but are not really labeled as such. I do a fair amount of cone 6 on wall tiles because they are smaller and I do not want large crystals on them. The french zinc I use on these tiles will disappear if you fire it over 2240F. Add more than 2% lithium, and it starts at 2220F. It both cases; copper seems to be affected more so than any other colorant: which I have to ASSUME is a chemical reaction between the low fire zinc, lithium, and copper.
Then there is zinc dust; which if you look at it too long while it is in the bucket: it begins to boil... LOL
_ personal observations and experiences--- but please note this is flat work.
Tom
Thank you for the insights: gives me a general direction to head in. Have made notes about reduction for years: but notes and doing it are two different realities. If I kick on the exhausts; it will completely turn over the air in the detached garage roughly every 60 seconds.
Some thoughts and experiences with copper and "boil off." I have tested nearly a dozen different zincs; most sent as free samples from various companies to be tested in crystalline glaze. "Yellow" zinc as we commonly call it will not boil off because it is made by the American process. This just means it is refined ore that has been roasted, washed, and put through a rotary kiln to burn off impurities: then finely ground. The only time there is a reaction with copper that gives the appearance of boiling off is when high amounts of lithium is used: so lower cone firings can be obtained. In reading numerous articles: in reality zinc does not reach its assigned boiling temp: it vaporizes before hand. When that occurs: it has an appearance of boiling: and high amounts of lithium contribute to that problem.
The real problem I have found is with french process zinc; which is made by capturing the vapors from zinc ore or zinc ingots that are intentionally high fired to cause vaporization. The primarily reason all french process zincs are extremely high in purity. Cerox 506 is in fact a french process zinc: but processed from an ore very low in sulphur (yellow color). Then it is highly calcined: the processing method makes it highly resistant to boiling off (vaporization.) Anyone using Cerox506 will probably never experience this problem unless they dump boat loads of lithium in it.
Then there are french process zincs that are cone 6 primarily: but are not really labeled as such. I do a fair amount of cone 6 on wall tiles because they are smaller and I do not want large crystals on them. The french zinc I use on these tiles will disappear if you fire it over 2240F. Add more than 2% lithium, and it starts at 2220F. It both cases; copper seems to be affected more so than any other colorant: which I have to ASSUME is a chemical reaction between the low fire zinc, lithium, and copper.
Then there is zinc dust; which if you look at it too long while it is in the bucket: it begins to boil... LOL
_ personal observations and experiences--- but please note this is flat work.
Tom
