JohnnyK Posted February 7, 2017 Report Share Posted February 7, 2017 Here is an interesting happening... I recently fired about a dozen of these "flowerpot gremlins" in a bisque/glaze firing to ^04. The dark red on the right was done with 2 coats of pure red iron oxide. The strange looking one on the left was done with 2 coats of red iron oxide and 3 coats of ^06 translucent matte glaze. Right came out pretty much as expected, but Left was a total surprise! The "matte" finished glossy and the color just blew me away. Any suggestions as to what might have happened. The clay was a ^5 B-Mix w/o grog. JohnnyK Link to comment Share on other sites More sharing options...
rakukuku Posted February 7, 2017 Report Share Posted February 7, 2017 I don't really know except that I have heard that iron oxide is actually a pretty powerful flux and may have glossed your matte glaze. Glazing never ceases to amaze. Link to comment Share on other sites More sharing options...
Mark C. Posted February 7, 2017 Report Share Posted February 7, 2017 looks like it fluxed out. Link to comment Share on other sites More sharing options...
Mark C. Posted February 7, 2017 Report Share Posted February 7, 2017 Was that one in a hot spot in Kiln??or near elements? Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted February 7, 2017 Report Share Posted February 7, 2017 Cone 04 is hotter than cone 06. My guess is that it's overfired. Or more likely, the glaze sold as a cone 06 matte is actually an under fired gloss at that temperature. Link to comment Share on other sites More sharing options...
neilestrick Posted February 7, 2017 Report Share Posted February 7, 2017 The matte glaze may have cooled too quickly, or it was over-fired. As for the iron, it looks exactly as I would expect under a glaze. The iron is taken into the glaze and diluted. You can see the dark areas where it's going black, which is where the iron is on thicker. It takes a lot of iron to go dark under a glaze when firing in oxidation. I used to use a 10% iron slip in reduction, I use a 22% iron slip in oxidation to get the same darkness. Personally, I would use an iron slip rather than straight iron. It's easier to get an even application, and won't go metallic and overload the glaze when thick. Link to comment Share on other sites More sharing options...
JohnnyK Posted February 8, 2017 Author Report Share Posted February 8, 2017 Thanks for all your input! We'll call this one a test. The next "test" will happen when I do a ^6 firing to see what happens to the dark red ones. If I want color, I will stick with underglazes and clear coats at ^06. JK Link to comment Share on other sites More sharing options...
JohnnyK Posted February 8, 2017 Author Report Share Posted February 8, 2017 Was that one in a hot spot in Kiln??or near elements? They were spread throughout the top shelf away from the elements... The top shelf was a half cone hotter than the bottom of the kiln according to my witness cones. Link to comment Share on other sites More sharing options...
glazenerd Posted February 8, 2017 Report Share Posted February 8, 2017 The top shelf was a half cone hotter than the bottom of the kiln according to my witness cones. Which is normal for most kilns. I learned along time ago to mix crystalline glaze for the entire kiln load and save the end of the batch for the bottom shelf of the kiln. I then added additional flux for that 1/2 cone colder spot. Actually I use a PH meter, and adjust the PH from 10.50 on the top, to 10.75 for the bottom shelf. Then again most glazes are not that picky. If you are dealing with some that are; this is one simple way to deal with them. Nerd By the way, if your clear has zinc in it: that will also play into bleeding (fluxing) out the color of iron. Link to comment Share on other sites More sharing options...
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