Test Glaze Firing

So I fired my test glaze pieces a couple of days ago.  I had numbered each piece on the bottom when I threw them so that I could track what I did to each one in terms of glaze thickness and placement on upper or lower shelves.  I wanted to test two different glazes:  the first, red chun, has always been a difficult glaze but when it works out well, it’s really beautiful and probably my favorite all round glaze.  However, instead of coming out red my pieces have been coming out rather gray and I couldn’t tell whether it was because the glaze was too thick, too thin, the kiln was too hot or too cold.  So I put one with thick glaze and one with thin glaze on each of the 3 shelves.  There’s about a whole cone’s difference in temperature between the top shelf in the kiln and the lower as you can see from the photo below.  

These are 5, 6, and 7 cone packs.  I'm trying to fire to cone 5.  I had to put a cone 7 in the kiln sitter and I think it still turned off the kiln a little too early. The single ones are cone 5 which I put right in the peep hole to be able to see it best while firing.  You can see that the cone 5 and cone 6 bent fairly nicely on the top shelf; just the cone 5 bent on the middle shelf; and the cone 5 on the bottom shelf only bent slightly.  

So . .

#1           red chun – thick glaze – bottom (cooler) shelf 

#3           red chun – thick glaze – top shelf

#4           red chun – thick glaze – middle shelf

#2           red chun – thin glaze – bottom shelf

#5           red chun – thin glaze – middle shelf

#7           red chun – thin glaze – top shelf

Starting from the left front they are numbered 1, 2, 4, and 3, 5 7 coming down from the back on the right.  The larger piece in the back is a red chun when behaving well - the color that I'm going for.  

There really seems to be almost no difference overall.  Each of them are fairly gray but each has a section that's got a little red tinge to it.  So I can't say that the test firing taught me anything.  Bummer.  It's still just red chun behaving badly.  Maybe it's just a bad batch.  I buy my glazes all mixed.  The glazes I'm accustomed to using are ones that my pottery teacher, Malley, mixed herself.  

The other glaze I wanted to test is the royal blue which has always been a really solid glaze, didn’t run much and showed off embellishments fairly well.  However, mine had been blistering and running and again, I didn’t know why. I think I did learn something from the royal blue test glazes.

It seems the thinner glaze on the cooler bottom shelf works best for the royal blue, though they all seem to have some blisters.  I really need to get this one right because I'm going to use it for a nice covered casserole dish and don't want to mess it up.  

Test The Glaze Firing

The witness cones on the far left are from the top shelf.  They are Cones 4, 5, and 6 and the two single ones are Cones 5.  Cones in the middle are also 4, 5, and 6.  You can see the 4 bent completely and the 5 just a little.  The cones on the right are all from the bottom shelf - again 4, 5, and 6, and the single one is a 5. But as you can see none of them really bent.   

These two pieces are both done in Celadon Froth.  There was no blistering but I need to make sure I hold it in the glaze long enough to get it thick.  You can see the blue is where it was double dipped and the brown is just a single dip.

Again, Celadon Froth - this was on the bottom shelf which only got to about Cone 4 but it came out nicely.  Even the Celadon Froth pieces on the top shelf came out fine - no blisters.  A great glaze!

This is red chun but it came out mostly grayish.  When not layered with other glazes it did not blister.  These were on the top shelf so it got hot enough and the glaze was plenty thick enough.  So maybe it got too hot or maybe it was too thick.  Gotta try to figure this one out because I love red chun when it works!

This is cappucino with the rim dipped in red chun.  This was on the top shelf and apparently got too hot because it's all blistered.  I think it's the cappucino that blistered because the pieces that were just done in chun and were on the top shelf didn't blister.

Another blistered cappucino and red chun.