Tuesday, 13 March 2012

Slipware Jugs. More Questions than Answers...

I seem to be having more than my fair share
of strange things happening in the workshop at the moment.
Have a look at these two jugs
 Both made at the same time.
Both slipped at the same time with the same bucket of green slip
 Both Biscuit fired in the same kiln
The one with the new elements
The one on the left as you look at them was laid on it's side
in the bottom of the kiln and the other stood upright
at the top of the kiln
 Both then glazed at the same time in the same bucket of glaze
 Both then come out of the firing exactly the same.
what the hell is going on ?
Am I the only person who makes these ? 
and this jug was in the same firing
but looks to be just slightly over fired.
I'm going to re fire this to see if I can get rid of the bubbles.
but I love the richness of the glaze, could it be that the glaze
is a bit on the thick side.?


Hollis Engley said...

That's pretty strange, isn't it? I mean the two different bisque-fired jugs. Maybe there was some carbon burnout that got into the dark one during the first firing, then burned off during the glaze firing? Bizarre. Don't know about the bubbles. I guess I'd worry if it was a whole kilnload. Maybe the glaze wasn't fully stirred when you dipped that one?

Tracey Broome said...

Are these bubbles because of the glaze you mentioned in the previous post bubbling? I once worked for a potter that had a shino that bubbled like mad. When I glazed I had to rub all of the pinholes out really well or the finished piece would have bubbles. AS for the darker bisque, I wonder if the kiln has hotter spots now. sometimes my bisque comes out looking like it was burnt if it was set too close to my burners. Really I have no idea though, just supposing....
I like the richness of the glaze on that last pitcher, even if it does have bubbles, just call it champagne glaze :)

madpotter1 said...

Paul, get a magnifying glass and look at the pinholes to determine if it's from the clay body or glaze. If you see craters in the clay body you know where to start. It might not be the glaze. Good luck!

LindaB said...

I think the pot that was at the top has overfired in the biscuit so that the slip has started to flux and go green. Overfiring the glaze may cause blisters as the flux starts to bubble.

Lori Buff said...

I see hotter spots in the bisque kiln all the time, it tends to be based on how the kiln is loaded, a tighter pack in one area can lead to more heat. It's normally not a great issue when the piece gets into the glaze kiln as you've seen.

DirtKicker Pottery said...

Did you (season) test fire your new elements with witness cones? Maybe you have one or two elements that are firing too hot.

Ron said...

Yes, I think the greener jug was fired hotter.

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