skuzbucket

Sorry, I unloaded a little before I remembered to snap a photo. the kiln was loaded pretty much as tight as possible given the way the dome curls downward at the arch- which is a slight pain in the butt but not horrible. certainly I was able to sneak pots put tight to the arch even at the top of the front stack... so there were two distinct sections to the stack- the back half like this:

and the front half composed 2/3 of pots on shelves with those two tall pillars off to the side- the front was the portion that got the most hot- was it stacked to a similar tightness as the back?- I pretty much think so, but the nature of the spaces was totally different- lots of choppy ones instead of tall columns as it was in the back... anyway- the front was massively more hot than than the back- cone 12. the back top was at about cone 8, bottom more like six.
this is so you can see what I'm talking about with the flue openings- lots in the floor, and a lot in the wall- so for this first fire, I had all the wall closed off, and most of the floor open. it was closed only on the right side near the firebox, because I anticipated using only one side of the kiln's potential fireboxes. but that's another story.

so it is clear that simply having most of the floor openings open in the back is not enough to move the heat back there-- ok, now we know. you can see what was open in the second photo. and remember that I yanked out the bag wall, which was a triangle-shape, taller in the back of the kiln. this would have been even worse, in hindsight. Stephen Mickmaster came to the unloading and suggested a small bag wall at the opposite of where I had had it even temporarily- a little deflector triangle at the front of the kiln- I may do that yet, but I like the rest of his suggestion better- open up some ports in the wall portion of the flue- and figure out a way to slow the flame- more of a skateboard of a target brick, or a rubble by Richard's idea, and of course more focus on air to the back in terms of flue openings... What I'll probably do is load a super-dense load of pots at that place where the bag-wall should be-

But here's the current bane of my existance: SCUM!! scum started when I asked my clay company to ad 5% redart to a "takamori" blend of porcelain. I had done this in grad school without problems.. big disclaimer there- so I had no qualms about ordering half a ton of the special blend from the clay company. they mixed up 2800 lbs for me, which I should have noted to them at the time... as it happened, something about the redart is causing a migration to the surface of the soluable calcium- as the pot dries, any oils on my fingers are making - not a resist- the opposite- a magnet for a scum to form. it shows up in the firing as a thin but distinctly gray layer. flowerpots below are from this firing. color is a little wacked but unintentional surface design is evident.

Below is a pot from a previous firing at Mt Hood college- in a salt kiln, and reduce-cooled, as this one was. Neely thought that perhaps the salt was aggravating it, essentially giving a light tacky surface on which the soot would settle and integrate with the surface. (I hope I got that straight- it was over a year ago). but there was no salt in this kiln... may I draw attention to the orange flashing at the center of the frame- I sanded some of these pots before firing them, to see what would happen- that orange is the most clean clay. then there's the scum, and an inbetween zone.

one photo shows the marks from my rubber rib- there at the top of the left-hand pot is where I pulled the rib upward. lower on that cylinder is a big gray band- why there and not elsewhere? anybody??


so here's the left hook: while I was at Penland, a friend used my studio, making pots with her own porcelain. here's one of hers:


there's no glaze on that pot. there is pretty much no chance for soluable soda ash or any of those quirky elements to be responsible for that mark. turn the pot right-side up in your head- looks to me like water dripping from the lip, absorbing into the clay, like she had washed the rim (with water from my tap...!), and then trimmed it- trimming off the bottom half of the "active ingredient"-- anybody? does this make sense? clearly, the marks on her pot are not scumming but flashing. but is is possible that the minerals in my water are reacting to the redart in this batch of clay to create an unusually subtle problem?? comments, please?!
I'm going to throw with distilled water for a while and see what happens-
next firing scheduled for the end of september.